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Indium gallium nitride

Indium gallium nitride (InGaN) is a ternary III-V semiconductor alloy composed of indium nitride (InN) and gallium nitride (GaN), with the chemical formula In_xGa_1-xN, where x denotes the indium mole fraction ranging from 0 to 1.^[1] This composition enables a tunable direct bandgap from approximately 0.7 eV (pure InN) to 3.4 eV (pure GaN), allowing efficient light emission and absorption across the ultraviolet, visible, and near-infrared spectra by adjusting the indium content.^[1]^[2] InGaN's high electron mobility, saturation velocity, thermal conductivity, and radiation resistance make it a pivotal material in optoelectronics, powering devices such as light-emitting diodes (LEDs), laser diodes, and photovoltaic cells.^[1]^[3] The material predominantly crystallizes in the wurtzite (hexagonal) structure, though cubic zincblende phases can be achieved via methods like plasma-enhanced molecular beam epitaxy on suitable substrates such as MgO.^[1]^[2] Its optical properties are enhanced by a bandgap bowing parameter of 1.4–2.8 eV, which facilitates precise wavelength control in quantum wells and nanostructures, enabling applications from blue-violet lasers (around 405 nm) to full-color displays and solid-state lighting.^[4]^[3] Electrically, InGaN supports both n-type (via nitrogen vacancies) and p-type (via magnesium doping) conductivity, with electron mobilities up to several thousand cm²/V·s, supporting high-frequency and high-power electronics like high-electron-mobility transistors (HEMTs).^[1]^[2] Despite its advantages, InGaN growth faces challenges including phase segregation at high indium fractions (>0.3), lattice mismatch with substrates like sapphire (leading to defects), and strong piezoelectric polarization fields that reduce device efficiency.^[1] Advances in epitaxial techniques, such as metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE), along with nanostructuring (e.g., nanowires and quantum dots), have mitigated these issues, enabling commercial breakthroughs like high-brightness blue LEDs that earned the 2014 Nobel Prize in Physics for related III-nitride developments.^[1]^[4] Beyond optoelectronics, InGaN's versatility extends to solar cells covering much of the solar spectrum, photodetectors, and emerging thermoelectric applications, underscoring its role in energy-efficient technologies.^[2]^[1]

Overview

Composition and nomenclature

Indium gallium nitride is a ternary III-V semiconductor alloy composed of indium nitride (InN) and gallium nitride (GaN), with the chemical formula \text{In}_x \text{Ga}_{1-x} \text{N}, where x represents the indium mole fraction ranging from 0 to 1.^[5] This notation describes a continuous solid solution series, enabling compositional tuning across the binary endpoints: pure GaN at x = 0 and pure InN at x = [1](/page/1).^[2] At the endpoints, GaN exhibits a wide direct bandgap of approximately 3.4 eV, suitable for ultraviolet applications, while InN features a narrow direct bandgap of about 0.7 eV, extending into the infrared spectrum.^[6] InGaN alloys, with intermediate x values, offer bandgap tunability from approximately 0.7 eV (near-infrared, for high indium content) to 3.4 eV (ultraviolet), providing versatility for optoelectronic devices across a broad spectral range.^[2] The material is commonly abbreviated as InGaN, a nomenclature derived directly from the elemental symbols indium (In), gallium (Ga), and nitrogen (N). This designation primarily refers to the wurtzite (hexagonal) crystal phase, which is thermodynamically stable under typical synthesis conditions, although zincblende (cubic) phases can be realized in nanostructures or specific epitaxial growths.^[7] The phase diagram of the In-Ga-N ternary system reveals a significant miscibility gap, particularly for compositions with high indium content (x > 0.2), arising from the large difference in formation energies and bond strengths between In-N and Ga-N bonds.^[8] This gap leads to thermodynamic instability and potential phase separation during growth at conventional temperatures (around 700–800°C), limiting uniform high-indium alloys without specialized techniques.^[9]

Historical development

The synthesis of gallium nitride (GaN) was first achieved in 1932 through the reaction of liquid gallium with ammonia gas at approximately 1000°C, producing polycrystalline material.^[4] Indium nitride (InN) followed in 1938, when Juza and Hahn prepared powdered InN by reacting indium with ammonia under similar high-temperature conditions.^[10] These early efforts laid the groundwork for III-nitride semiconductors, though the materials exhibited poor crystallinity and were limited to basic powder forms. Initial explorations of InGaN alloys emerged in the 1970s, with the first reports of thin films grown by electron-beam evaporation in 1972 and 1975, enabling optical absorption studies that confirmed bandgap tunability with indium composition.^[11] By the 1980s, metalorganic chemical vapor deposition (MOCVD) advanced the growth of InGaN layers, allowing for better control over alloy composition despite challenges like phase separation.^[12] A pivotal demonstration of GaN's potential came in 1971, when Pankove and colleagues reported green electroluminescence from zinc-doped GaN diodes, marking the first observation of light emission in a nitride semiconductor.^[13] However, early InGaN films suffered from high defect densities exceeding 10^{10} cm^{-2}, limiting efficiency due to non-radiative recombination.^[14] The 1990s brought transformative breakthroughs, particularly through Shuji Nakamura's work at Nichia Corporation, where high-quality InGaN/GaN multiple quantum wells were developed using MOCVD on sapphire substrates with a low-temperature GaN buffer layer. This enabled the first efficient blue double-heterostructure light-emitting diode (LED) in 1993, achieving room-temperature band-to-band emission with external quantum efficiencies around 1%.^[11] These innovations, shared in seminal publications, culminated in the 2014 Nobel Prize in Physics awarded to Nakamura, Isamu Akasaki, and Hiroshi Amano for inventing efficient blue LEDs.^[15] Research evolved rapidly in the 2000s, shifting from defect-laden films to high-efficiency structures through refined growth techniques that reduced dislocation densities to 10^8 cm^{-2} or lower, enhancing radiative recombination and enabling commercial blue and green LEDs.^[16] Post-2010 advancements focused on high-indium-content InGaN (over 40% In), overcoming thermodynamic instabilities via molecular beam epitaxy (MBE) to access infrared wavelengths below 1 eV, as demonstrated in InN quantum dots on InGaN layers for potential photovoltaic and sensing applications.^[17] Influential reviews highlight ongoing progress in strain management and nanostructuring, positioning high-In InGaN for flexible electronics and extended-spectrum optoelectronics as of 2023.

Material properties

Crystal structure and lattice parameters

Indium gallium nitride (InGaN) alloys primarily adopt the wurtzite (hexagonal) crystal structure, which is the stable phase under typical growth conditions, while the zincblende (cubic) phase exists as a metastable form. The wurtzite structure is characterized by lattice constants that vary linearly between those of the binary compounds GaN and InN, with GaN exhibiting a \approx 3.189 Å and c \approx 5.185 Å, and InN showing a \approx 3.533 Å and c \approx 5.693 Å.^[18]^[18] The significant lattice mismatch of approximately 11% between GaN and InN introduces strain in In_xGa_{1-x}N alloys, particularly as the indium content x increases, which can affect phase stability and defect formation. To account for nonlinear deviations from Vegard's law in the lattice parameters, a bowing parameter is employed, with reported values of \delta_a = -0.004 Å for the in-plane constant a and \delta_c = 0.042 Å for the out-of-plane constant c, allowing the lattice constants to be modeled as a(x) = (1-x)a_{\text{GaN}} + x a_{\text{InN}} + \delta_a x(1-x) and similarly for c(x).^[19]^[20] In heteroepitaxial growth on sapphire substrates, common threading dislocations arise due to the underlying lattice mismatch between the InGaN layer and the substrate, with densities typically ranging from $10^8 to $10^{10} cm^{-2}. Additionally, in alloys with high indium content (x > 0.35), phase separation occurs, leading to compositional inhomogeneities and the formation of indium-rich regions.^[21]^[22] The thermal expansion coefficient along the a-axis for InGaN alloys is approximately \alpha_a \approx 3.2 \times 10^{-6} K^{-1}, similar to that of GaN, influencing strain during temperature variations in processing. Phase diagrams reveal an immiscibility gap for x > 0.2 at common growth temperatures (around 700–800°C), promoting phase separation in indium-rich compositions and limiting uniform alloy formation without specialized techniques.^[23]^[24]

Optical and electronic properties

Indium gallium nitride (InGaN) is a direct bandgap semiconductor, with its bandgap energy tunable across a wide range by varying the indium composition x in \mathrm{In}_x\mathrm{Ga}_{1-x}\mathrm{N}. The bandgap E_g(x) follows a bowing model given by E_g(x) = 3.4(1-x) + 0.7x - 1.43x(1-x) eV, where 3.4 eV corresponds to GaN and 0.7 eV to InN (with bowing parameters reported in the range of 1.4–2.8 eV accounting for variations due to strain and composition), enabling emission from ultraviolet wavelengths (~365 nm for GaN) to near-infrared (~1.8 μm for InN).^[25] This tunability arises from the nonlinear compositional dependence captured by the bowing parameter of approximately 1.43 eV, which accounts for deviations from Vegard's law due to alloy disorder and strain effects. Excitonic effects are prominent, with binding energies ranging from ~20 to 50 meV, enhancing radiative recombination efficiency particularly in quantum-confined structures.^[26] Optically, InGaN exhibits a refractive index n that varies from approximately 2.4 for low-In compositions to 2.9 for high-In content, with wavelength dependence showing dispersion near the bandgap.^[27] The material demonstrates strong light-matter interactions, characterized by an absorption coefficient \alpha > 10^5 cm^{-1} just above the bandgap, typical of direct transitions in III-nitride alloys. Photoluminescence in InGaN quantum wells shows high efficiency due to carrier localization at potential fluctuations, mitigating nonradiative recombination despite intrinsic polarization fields.^[27] Electronically, InGaN supports high electron mobilities \mu_e reaching up to 2000 cm²/V·s in strained layers, benefiting from reduced alloy scattering in low-In compositions, while hole mobilities \mu_h remain lower at ~10–50 cm²/V·s due to heavy effective masses.^[28] Spontaneous and piezoelectric polarization fields, up to 1 MV/cm in strained heterostructures, induce a quantum-confined Stark effect that spatially separates electron and hole wavefunctions, redshifting emission and reducing oscillator strength.^[29] Doping presents challenges: n-type doping with silicon is straightforward, with a shallow donor level of ~20 meV enabling carrier concentrations exceeding 10¹⁹ cm⁻³, whereas p-type doping with magnesium suffers from a deep acceptor level of ~200 meV, leading to activation efficiencies below 1% at room temperature and compensation by native donors limiting hole concentrations to ~10¹⁷ cm⁻³.^[30]

Synthesis and fabrication

Growth techniques

Indium gallium nitride (InGaN) thin films and nanostructures are primarily synthesized using epitaxial growth techniques to achieve high-quality crystalline layers suitable for device applications. The choice of method depends on requirements for growth rate, compositional control, and defect density, with metalorganic chemical vapor deposition (MOCVD) being the most widely adopted due to its scalability and compatibility with industrial production. MOCVD involves the reaction of metalorganic precursors in a hydrogen or nitrogen carrier gas ambient. Common precursors include trimethylgallium (TMGa) for gallium, trimethylindium (TMIn) for indium, and ammonia (NH₃) for nitrogen, delivered at controlled flow rates to tune the In/Ga ratio. Growth temperatures typically range from 700–900 °C to enable sufficient indium incorporation while minimizing InN decomposition, which occurs above approximately 650 °C.^[31]^[32] Reactor pressures vary between 50–200 Torr in low-pressure variants for improved uniformity and reduced parasitic reactions, and up to atmospheric pressure (760 Torr) for higher throughput, though the latter can lead to rougher surfaces.^[31] Growth rates are generally 0.5–2 μm/h, influenced by precursor partial pressures and V/III ratio (typically 1000–5000). Challenges include phase separation in high-In-content alloys (>30% In) due to the miscibility gap, often mitigated by pulsed precursor delivery or multi-step temperature profiles.^[31] Molecular beam epitaxy (MBE) provides atomic-layer precision under ultra-high vacuum conditions (10⁻¹⁰ Torr base pressure). Elemental gallium and indium are supplied via Knudsen effusion cells, while reactive nitrogen is generated from an RF plasma source operating at 300–1000 W power using N₂ gas. Substrate temperatures for InGaN growth are maintained between 500–800 °C, with lower temperatures favoring higher indium content but risking defect formation.^[33] Growth proceeds in metal-rich or nitrogen-rich regimes, with rates of 0.1–1 μm/h determined by beam equivalent pressures (typically 5×10⁻⁷ to 10⁻⁶ Torr for metals). Plasma-assisted MBE (PAMBE) variants enable in-situ monitoring via reflection high-energy electron diffraction (RHEED) for abrupt interfaces. This technique excels in nanostructure growth, such as quantum dots, but is limited by slower rates compared to vapor-phase methods.^[34] Hydride vapor phase epitaxy (HVPE) is employed for rapid deposition of thick InGaN layers, particularly on templated substrates. Chlorides (GaCl and InCl) are generated in situ by reacting HCl gas with metallic gallium and indium sources, then transported with NH₃ and H₂ carrier gas to the reactor. Growth temperatures range from 600–900 °C, balancing volatility of indium chlorides and nitrogen incorporation.^[35] Unlike MOCVD, HVPE achieves exceptionally high growth rates exceeding 10 μm/h—up to 12 μm/h for In-rich compositions at 600 °C—making it ideal for freestanding substrates or buffers.^[35] The process operates at near-atmospheric pressure (760 Torr), with horizontal or vertical reactor geometries to control precursor mixing. HVPE is less common for thin InGaN films due to challenges in compositional uniformity but is valuable for cost-effective thick-layer production.^[36] Common substrates for these techniques include c-plane sapphire (Al₂O₃ (0001)), which offers chemical stability and low cost despite a 14% lattice mismatch with InGaN, necessitating low-temperature buffers to manage strain. Silicon carbide (SiC) provides a closer lattice match (3–4% mismatch) and higher thermal conductivity, reducing defect propagation. GaN templates or homoepitaxial substrates minimize mismatches, though heteroepitaxy on foreign substrates introduces thermal expansion differences (Δα ≈ 50% for sapphire-InGaN), leading to cracking or bowing that is often addressed via compliant interlayers.^[37]^[38]

Doping and compositional control

Compositional control in indium gallium nitride (InGaN), denoted as In_xGa_{1-x}N, is primarily achieved through precise adjustment of precursor flow ratios during metalorganic chemical vapor deposition (MOCVD). The trimethylindium (TMIn) to triethylgallium (TEGa) + TMIn ratio directly influences the indium incorporation, allowing variation of the composition parameter x. High vapor-to-group III (V/III) ratios, typically exceeding 1000, are essential for maintaining nitrogen-rich growth conditions, which suppress indium droplet formation and promote uniform alloy formation in In-rich regimes (x > 0.3). A key challenge in achieving higher indium contents is thermal desorption of indium atoms at elevated growth temperatures, which limits x to below 0.3 under standard conditions above 580°C. This desorption arises from the lower bond strength of In-N compared to Ga-N, necessitating low-temperature growth strategies (below 700°C) to enhance indium stability and enable x up to 0.4 or higher, albeit at the cost of reduced surface mobility and increased defect densities.^[33] n-type doping in InGaN is effectively realized using silicon (Si) or germanium (Ge) as group IV donors, with incorporation efficiencies approaching 100% at carrier concentrations of $10^{18} to $10^{20} cm^{-3}. Si doping via silane is straightforward but can induce three-dimensional growth and tensile stress at levels above $1.9 \times 10^{19} cm^{-3}, while Ge doping with germane allows higher concentrations without significant degradation compared to Si.^[39] p-type doping employs magnesium (Mg) as the primary acceptor, but Mg atoms form passivating Mg-H complexes during growth in hydrogen-containing environments like MOCVD. Activation of these acceptors requires post-growth high-temperature annealing above 800°C, typically for several minutes in a nitrogen ambient, to dissociate the complexes and achieve hole concentrations exceeding $10^{18} cm^{-3}.^[40]^[41] Advanced techniques address segregation effects in InGaN alloys, where differences in InN and GaN formation enthalpies and vapor pressures cause indium clustering and compositional gradients, particularly under compressive strain. Superlattice buffers, such as alternating InGaN/GaN layers, manage strain by promoting controlled relaxation through misfit dislocations, reducing threading defect propagation and stabilizing high-indium compositions. Recent plasma-assisted molecular beam epitaxy (PAMBE) methods enable growth of InGaN with x > 0.5 at low temperatures (400–670°C) via metal flux modulation and excess indium coverage, minimizing desorption while achieving partial strain relaxation over thicknesses of 350 nm or more.^[42] As of 2025, further progress includes optimized MOCVD and MBE techniques for high-In InGaN enabling efficient red LEDs, reducing phase separation through strain management strategies.^[43]

Applications

Optoelectronic devices

Indium gallium nitride (InGaN) is a cornerstone material in optoelectronic devices due to its tunable direct bandgap, which enables efficient emission and detection across ultraviolet to green wavelengths. InGaN-based structures, particularly when integrated with gallium nitride (GaN), form the active regions of high-performance light-emitting and light-detecting components. These devices leverage the material's strong piezoelectric and spontaneous polarization fields to enhance carrier confinement, though challenges like efficiency droop persist.^[44] Light-emitting diodes (LEDs) utilizing InGaN/GaN multiple quantum wells (MQWs) are pivotal for blue and green emission, with peak wavelengths around 450 nm for blue devices. These MQWs achieve internal quantum efficiencies (IQE) up to 80% at low current densities, attributed to improved indium incorporation and reduced defect densities in the quantum wells. Efficiency droop, a reduction in quantum efficiency at high currents, is mitigated through techniques like polarization doping in the barriers and electron blocking layers, which enhances hole injection and reduces carrier overflow by up to 25%.^[44]^[45] Laser diodes based on InGaN exploit similar MQW active regions for coherent emission in the blue-violet spectrum, notably at 405 nm. Edge-emitting InGaN laser diodes exhibit threshold current densities ranging from 1 to 5 kA/cm², enabling continuous-wave operation with output powers exceeding 1 W under optimized ridge waveguide designs. Recent advancements post-2020 have focused on vertical-cavity surface-emitting lasers (VCSELs), where semipolar GaN substrates and dielectric mirrors have enabled room-temperature lasing at green wavelengths around 515 nm, with threshold currents as low as 4 mA.^[46]^[47]^[48] Photodetectors employing InGaN/GaN heterostructures excel in ultraviolet (UV) detection, benefiting from the GaN's 3.4 eV bandgap for solar-blind operation below 365 nm. These devices, often configured as p-i-n junctions, demonstrate responsivities greater than 0.1 A/W at UV wavelengths, with peak values reaching 0.22 A/W near 378 nm under zero bias, due to efficient carrier collection in the intrinsic InGaN layer.^[49]^[50] Key performance metrics underscore InGaN's impact: blue LEDs achieve wall-plug efficiencies approaching 50%, reflecting high electrical-to-optical conversion when accounting for extraction losses. In white LEDs, InGaN blue emitters combined with phosphor conversion yield high color rendering indices above 90, enabling applications in solid-state lighting with luminous efficacies over 300 lm/W. The bandgap tunability of InGaN, spanning 1.9 to 3.4 eV, underpins these wavelength-specific optimizations.^[51]^[51]

Photovoltaic and energy applications

Indium gallium nitride (InGaN) alloys are promising for photovoltaic applications due to their tunable direct bandgap spanning 0.7 eV (for InN) to 3.4 eV (for GaN), enabling full-spectrum solar absorption in multi-junction tandem configurations.^[5] In multi-junction solar cells, InGaN layers can serve as top junctions to capture high-energy photons, while lower-bandgap variants target the infrared spectrum, theoretically exceeding 50% power conversion efficiency by minimizing thermalization losses across the AM1.5G spectrum. Experimental p-i-n InGaN solar cells, however, achieve modest efficiencies of approximately 2-4% under AM1.5G illumination, primarily limited by high defect densities, such as threading dislocations from lattice mismatch during epitaxial growth on GaN substrates.^[52] Bandgap grading in InGaN layers enhances broadband absorption by creating a compositional gradient that funnels carriers toward the junction, reducing recombination losses and improving charge collection.^[53] This approach has been integrated into hybrid solar cells, where InGaN is combined with silicon or gallium arsenide bottom cells via epitaxial transfer or direct bonding, leveraging InGaN's UV response to boost overall efficiency beyond single-junction limits.^[54] Such hybrids address spectral mismatch, with simulated efficiencies reaching up to 26% when polarization effects are minimized.^[55] In power electronics, InGaN-channel high-electron-mobility transistors (HEMTs) exploit the material's high electron mobility and breakdown strength for high-voltage applications, achieving off-state breakdown voltages exceeding 600 V through optimized barrier designs and strain management.^[56] These devices benefit from InGaN's wider bandgap compared to pure GaN channels, enabling operation at elevated temperatures, though thermal management remains critical to mitigate self-heating in high-power scenarios like electric vehicle inverters. Emerging energy applications include photoelectrochemical water splitting, where InGaN photoanodes facilitate hydrogen evolution under ultraviolet illumination, with reported rates of 1-10 μmol/h/cm² in acidic electrolytes due to efficient band alignment for oxygen evolution.^[57] Doping and nanostructuring further stabilize these photoanodes against photocorrosion, enhancing long-term hydrogen production for renewable fuel generation.^[58] InGaN/GaN superlattices are also explored for thermoelectric energy harvesting owing to their high-temperature stability and low thermal conductivity, with studies as of 2024 showing enhanced thermoelectric figure of merit through interfacial polarization effects.^[59]

Nanostructured and quantum devices

Indium gallium nitride (InGaN) quantum heterostructures, particularly InGaN/GaN quantum wells with thicknesses typically ranging from 2 to 10 nm, enable strong quantum confinement of carriers, enhancing radiative recombination efficiency in optoelectronic devices.^[5] These thin wells, grown via epitaxial methods, exhibit indium clustering due to phase separation during deposition, forming localized states that trap excitons and reduce non-radiative losses from defects.^[60] This localization improves internal quantum efficiency, especially in high-indium compositions where strain and compositional fluctuations create potential minima for carrier confinement.^[61] Self-assembled InGaN nanorods and nanowires, often fabricated through selective-area growth on patterned substrates, feature diameters of 50-200 nm and exhibit significantly reduced dislocation densities below 10^6 cm^{-2} compared to planar films.^[62] This reduction occurs as growth proceeds laterally from the mask openings, bending and annihilating threading dislocations at the nanorod sidewalls, leading to nearly defect-free cores that enhance optical and electrical performance.^[63] Such structures leverage the high aspect ratios of nanorods to minimize strain relaxation issues inherent in bulk InGaN layers. Embedded InGaN quantum dots (QDs), either site-controlled within nanowires or formed via self-assembly in quantum wells, serve as efficient single-photon sources with emission linewidths around 50 meV, reflecting their discrete energy levels and reduced inhomogeneous broadening.^[64] These QDs, with sizes on the order of 10-20 nm, demonstrate antibunching in second-order correlation measurements, confirming non-classical light emission suitable for quantum information applications.^[65] Colloidal InGaN QDs, synthesized in solution, offer additional tunability but are less common due to stability challenges in nitride systems. In nanostructured InGaN devices, polarization-induced charges play a key role, generating two-dimensional electron gases (2DEGs) at heterointerfaces within nanowires, which boost carrier injection and conductivity for high-performance operation.^[66] These features enable applications in flexible displays, where vertical InGaN/GaN nanowire LEDs maintain efficiency under bending due to their release from rigid substrates.^[67] Additionally, InGaN nanostructures support biosensors, exploiting surface polarization effects for sensitive detection of biomolecules via changes in 2DEG conductivity.^[68]

Health and environmental aspects

Toxicity and biological effects

Indium gallium nitride (InGaN), as a ternary alloy containing indium, presents potential health risks primarily associated with its indium content, though specific toxicological data on InGaN itself remain limited. Indium ions (In³⁺) released from such compounds can bioaccumulate in vital organs, leading to nephrotoxicity and hepatotoxicity. For instance, exposure to soluble indium compounds like indium chloride has been shown to cause kidney damage and liver necrosis in animal models, with intravenous administration in mice resulting in significant organ impairment. The oral LD50 for elemental indium in rats exceeds 2,000 mg/kg, indicating relatively low acute oral toxicity, but chronic exposure poses greater concerns for systemic effects including impacts on the heart and bone marrow. In contrast, gallium nitride (GaN), the other primary component of InGaN, exhibits low toxicity and high biocompatibility, with studies demonstrating no adverse effects in cellular and animal assays even after surface functionalization. While synergistic toxicity in InGaN alloys has been hypothesized due to compositional interactions, direct evidence is scarce, and risks are generally extrapolated from indium-dominant compounds. Nanoparticle forms of InGaN, such as nanorods used in advanced devices, may amplify toxicity through increased surface area and bioavailability. Analogous indium-containing nanoparticles, like indium oxide nanocubes, induce cytotoxicity and apoptosis in human lung epithelial cells (A549) via oxidative stress mechanisms, with half-maximal inhibitory concentrations (IC50) in the range of 10–50 μg/mL after 24-hour exposure. These particles elevate reactive oxygen species (ROS) levels more than twofold compared to controls at concentrations of 25–50 μg/mL, accompanied by glutathione depletion, reduced superoxide dismutase activity, and lactate dehydrogenase leakage indicating membrane damage. Inflammation is also triggered, potentially exacerbating pulmonary responses. Although specific studies on InGaN nanorods are lacking, their structural similarity to other III-nitride nanostructures suggests comparable risks, particularly for inhalation of aerosols during synthesis or processing. Exposure routes for InGaN primarily involve inhalation and dermal contact during fabrication processes like metal-organic chemical vapor deposition (MOCVD), where volatile indium precursors such as trimethylindium generate fumes. The Occupational Safety and Health Administration (OSHA) sets a permissible exposure limit (PEL) of 0.1 mg/m³ as an 8-hour time-weighted average for indium and its compounds, aimed at preventing respiratory irritation and systemic uptake. Dermal exposure may cause skin irritation from dust or particulates, though absorption is limited compared to inhalation. No dedicated regulations exist for InGaN, but guidelines for analogous materials like gallium arsenide (PEL 0.002 mg/m³ as arsenic) underscore the need for engineering controls in semiconductor production. Epidemiological evidence on InGaN is absent, reflecting its niche industrial use, but human studies on related indium compounds provide cautionary insights. Workers exposed to indium-tin oxide (ITO) in manufacturing settings have developed "indium lung disease," characterized by interstitial fibrosis, emphysema, and pulmonary alveolar proteinosis, with symptoms including dyspnea and reduced lung function after cumulative exposures below 0.1 mg/m³. High-resolution computed tomography reveals subclinical interstitial changes in exposed individuals, and serum markers like KL-6 are elevated in over 40% of cases. These findings, derived from cohorts in Japan and Korea, highlight the potential for irreversible lung damage from chronic low-level indium exposure, warranting surveillance for InGaN handlers.

Handling and disposal guidelines

When handling indium gallium nitride (InGaN) in laboratory or industrial settings, appropriate personal protective equipment (PPE) is essential to minimize exposure risks. Workers should wear chemical-resistant gloves, such as nitrile or butyl rubber, to prevent skin contact, particularly with indium-containing precursors used in synthesis, as these can be absorbed through the skin.^[69] NIOSH-approved respirators with particulate filters (e.g., N95 or higher) are recommended for tasks involving dust or aerosols, and operations like powder handling or etching should be conducted in a fume hood or under local exhaust ventilation to avoid inhalation of fine particles.^[70] Eye protection, such as safety goggles, is also required due to potential irritation from dust.^[71] For storage, InGaN materials, particularly in powder or thin-film form, should be kept in a cool, dry environment under an inert atmosphere such as nitrogen (N₂) to prevent oxidation and degradation.^[72] Temperatures should be maintained below 50°C to preserve stability, especially for powders susceptible to thermal stress. Containers must be sealed and labeled, stored away from incompatible substances like strong oxidizers or acids.^[73] Disposal of InGaN waste requires classification as hazardous due to the presence of indium, which may exhibit toxicity characteristics under environmental regulations. In the United States, indium-containing wastes may be classified as hazardous under RCRA if they are listed or exhibit other characteristics (e.g., ignitability, corrosivity), though not via TCLP for indium. Proper classification requires testing and consultation with EPA or state environmental agencies; treatment such as stabilization with cement or incineration may be needed if hazardous prior to landfilling. Recycling is preferred and can be achieved through hydrometallurgical methods, including acid leaching with hydrochloric acid to recover indium and gallium, as demonstrated in processing LED scraps containing InGaN.^[74] All disposal must comply with local, state, and federal guidelines, including proper manifesting and transport to licensed facilities.^[70] Regulatory frameworks emphasize exposure control for indium compounds in InGaN. Under EU REACH, indium substances, including those in semiconductors like InGaN, are registered and subject to supply chain communication requirements, with no specific use restrictions but ongoing evaluation for potential authorizations.^[75] In the workplace, monitoring for airborne indium is mandated, with the OSHA permissible exposure limit (PEL) set at 0.1 mg/m³ as an 8-hour time-weighted average to protect against respiratory effects.^[76] Regular air sampling and medical surveillance are recommended for exposed personnel.

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Near-infrared InN quantum dots on high-In composition InGaN
Apr 5, 2013 · We report the growth of InN quantum dots (QDs) on thick InGaN layers with high In composition (>50%) by molecular beam epitaxy.Missing: post- | Show results with:post-
[18]
GaN Group @ TTU (III-N parameters)
Wurtzite polytype: GaN. AlN ; Bandgap energy (eV). 3.44 (300 K). 6.20 (300K) ; Lattice Constant. (Å). a = 3.189. c = 5.185. a = 3.112. c = 4.982 ; Thermal ...Missing: ac | Show results with:ac
[19]
Improved Quality of InN Thin Films Using a Thin InGaN Compressive ...
Jul 9, 2024 · (5) As a consequence, the in-plane lattice mismatch of ∼11% with GaN and ∼13% with AlN causes stress, followed by relaxation, resulting in a ...
[20]
Phase stability, chemical bonds, and gap bowing of alloys
Jul 27, 2006 · We found a value of for the gap bowing parameter giving support to the recent smaller band gap bowing findings. We emphasize that other ...
[21]
Effect of varying threading dislocation densities on the optical ...
Nov 16, 2023 · However, the large lattice mismatch between sapphire and GaN (16%)1 leads to a dislocation density of at least ∼108 cm−2 in the epitaxial layers ...INTRODUCTION · II. EXPERIMENTAL DETAILS · III. RESULTS AND DISCUSSION
[22]
Phase separation and ordering in InGaN alloys grown by molecular ...
In this study, we investigated phase separation and long-range atomic ordering phenomena in InGaN alloys produced by molecular beam epitaxy.
[23]
Temperature dependence of the thermal expansion of GaN
The thermal expansion coefficients (TECs) along the a and c axis of GaN ( α a and α c ) have been studied experimentally during the past years using different ...<|separator|>
[24]
Thermodynamic stability and redistribution of charges in ternary ...
The phase diagrams obtained indicate that AlxGa1−x N is stable in the entire range of x, whereas the miscibility gap corresponds to 0.2 < x < 0.69 for InxGa1−x ...
[25]
Band parameters for nitrogen-containing semiconductors
Sep 15, 2003 · We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to ...Missing: InGaN | Show results with:InGaN
[26]
Prediction of low threshold current density in InGaN-AlGaN quantum ...
The exciton binding energies in InGaN-AlGaN quantum wire are calculated to be 30-60 meV as wire width reduces from 150 angstrom to 50 angstrom.
[27]
Optical properties of InGaN thin films in the entire composition range
Mar 26, 2018 · The optical properties of thick InGaN epilayers, with compositions spanning the entire ternary range, are studied in detail.INTRODUCTION · III. RESULTS AND DISCUSSION · IV. CONCLUSIONS
[28]
Electron mobility in modulation doped AlGaN/GaN and InGaN/GaN ...
Aug 7, 2025 · ... mobility changes from 20 cm 2 / Vs to 2000 cm 2 / Vs . 9 .9904e+20 ... It is seen that electron mobilities upto 40 × 103 cm2/Vs can be ...
[29]
Quantum-Confined Stark Effect due to Piezoelectric Fields in GaInN ...
Our calculation suggests that an electric field of 1.08 MV/cm is induced by the piezoelectric effect in strained Ga 0.87 In 0.13 N grown on GaN.
[30]
Improvement on InGaN‐based light emitting diodes using p‐GaN ...
Feb 19, 2014 · The activation energy of the most commonly used acceptor dopant (Mg) in GaN is ∼200 meV 1-3, which leads to a very low Mg activation efficiency.
[31]
Recent advances and challenges in the MOCVD growth of indium ...
Sep 2, 2025 · This article discusses the key challenges and the recent breakthroughs in realizing high-quality indium (In)-rich indium gallium nitride ...
[32]
MOCVD growth of InN thin films at different temperatures using ...
Feb 15, 2025 · We report on the MOCVD growth of InN thin films at three temperatures (ie, 570 °C, 585 °C, and 600 °C) using a pulsed trimethylindium (TMIn) approach.
[33]
Molecular Beam Epitaxy Growth of GaN/InGaN Heterostructures ...
Mar 7, 2024 · Molecular beam epitaxy is applied for the GaN/InGaN growth under In-bilayer stabilized conditions, which require substrate temperatures above 580 °C for ...
[34]
Strain-induced formation of self-assembled InGaN/GaN superlattices ...
We propose that the vertical phase separation observed in the SASL structure is caused by high-temperature growth and intensified by strain. This work provides ...
[35]
High rate InN growth by two-step precursor generation hydride ...
Jul 15, 2015 · The growth rate reached 12.4 μm/h at a growth temperature of 600 °C, and the rate was observed to decrease above this temperature. Specular InN ...
[36]
Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN
We managed to increase the deposition rate of the GaN HVPE process by a factor of 5. Also the number of crystal defects improved a 1000 times and we managed ...
[37]
GaN Epitaxial Growth on Sapphire Substrate for Blue LED
Mar 25, 2022 · MOCVD GaN epitaxial growth on sapphire substrate with quantum efficiency ~50 can be backside polished for laser lift-off for blue LED ...
[38]
Demonstration of epitaxial growth of strain-relaxed GaN films on ...
Jun 3, 2021 · Epitaxial growth of GaN films and InGaN/GaN MQWs. GaN films were grown on graphene/SiC substrates by an AIXTRON 3 × 2″ FT MOCVD system.
[39]
High Si and Ge n-type doping of GaN doping - Limits and impact on ...
Mar 19, 2012 · We report on GaN n-type doping using silane, germane, and isobutylgermane as Si and Ge dopants, respectively. A significant increase in tensile stress during ...
[40]
Hydrogen Can Passivate Carbon Impurities in Mg-Doped GaN - PMC
Feb 10, 2020 · The rapid thermal annealing is carried out in a nitrogen environment at a temperature of 800 °C for 3 min to de-passivate the Mg–H complexes.
[41]
Improvement of p-Type AlGaN Conductivity with an Alternating Mg ...
We prepared seven p-type AlGaN samples of ~25% in Al content, including six samples with Mg-doped/un-doped AlGaN alternating-layer structures of different ...
[42]
[PDF] High In-content InGaN layers synthesized by plasma-assisted ... - arXiv
In this work, we address the interplay between In incorporation and strain relaxation in high-In-content InGaN layers grown by PAMBE on GaN. In particular, we ...Missing: advanced control
[43]
[PDF] Development of gallium-nitride-based light-emitting diodes (LEDs ...
The IQE of today's best LEDs has reached values higher than 80% for blue 450 nm LEDs at low current densities. (<30 A cm 2). Further improvements towards 100 ...
[44]
(PDF) Droop Improvement in InGaN/GaN Light-Emitting Diodes by ...
Aug 6, 2025 · Numerical results show that the internal quantum efficiency of polarization doped LED structures are improved by 25% as compared to un-doped ...
[45]
[PDF] Simulation and Optimization of 420 nm InGaN/GaN Laser Diodes
In n-type material, the Si donor activation energy is about 20 meV.19. Our electron mobility values are 200 cm2/Vs for GaN, 100 cm2/Vs for InGaN, and 30 cm2/Vs ...
[46]
Efficiency droop in InGaN/GaN blue light-emitting diodes
Aug 15, 2013 · p-doped barriers. According to Ref. 54, droop can be mitigated by p-doping all QBs. The current density at the efficiency peak can be moved ...
[47]
Green Vertical-Cavity Surface-Emitting Lasers Based on InGaN ...
Oct 9, 2023 · In 2020, Sony utilized (20-21) semipolar GaN substrate to grow InGaN/GaN MQWs and achieved lasing of green VCSEL at 515 nm, but the threshold ...Missing: post- | Show results with:post-
[48]
InGaN/GaN MQW p–n junction photodetectors - ScienceDirect
Furthermore, it was found that the maximum responsivity was 1.28 and 1.76 A/W with a 0.1 and 3 V applied reverse bias, respectively. Introduction. III–V nitride ...
[49]
Design and Simulation of InGaN/GaN p–i–n Photodiodes
Jan 24, 2018 · Lu et al.8 reported a peak responsivity of 0.22 A W−1 at 378 nm in an unbiased InGaN p–i–n photodetector with intrinsic ...
[50]
[PDF] EFFICIENT BLUE LIGHT-EMITTING DIODES LEADING TO BRIGHT ...
Oct 7, 2014 · Cooper Hewitt in 1900, reaches an efficiency of 70 lm/W. White LEDs currently reach more than 300 lm/W, representing more than 50% wallplug ...
[51]
Guidelines and limitations for the design of high-efficiency InGaN ...
As a result of the miscibility gap between InN and GaN, indium-rich InGaN films commonly display compositional fluctuation or complete phase separation [34].
[52]
Numerical Study of a Solar Cell to Achieve the Highest InGaN Power ...
A current density of 52.95 mA/cm2, with an efficiency of over 85%, is determined for a PiN structure with an InGaN step-graded bandgap absorption layer and ...
[53]
[PDF] Heterogeneous Integration of Thin-Film InGaN-Based Solar Cells on ...
One interesting way to make these hybrid systems is to grow and process the InGaN-based solar cell, release it from the growth wafer and bond it to a foreign ...
[54]
III-Nitride/Si Tandem Solar Cell for High Spectral Response
Dec 14, 2019 · A remarkable conversion efficiency of 25.6% and 26.1% are achieved with & without polarization effect, respectively and became a potential ...<|control11|><|separator|>
[55]
High performance InGaN double channel high electron mobility ...
Dec 4, 2018 · Therefore, the off-state breakdown voltages of the InGaN DC HEMTs were measured with the small gate-drain-distance (LGD = 1.5, 3, and 5 μm) as ...
[56]
Highly Stable Photoelectrochemical Water Splitting and Hydrogen ...
Aug 6, 2013 · We report on the first demonstration of stable photoelectrochemical water splitting and hydrogen generation on a double-band photoanode in acidic solution.Supporting Information · Author Information · Acknowledgment · References
[57]
Recent advances in InGaN nanowires for hydrogen production ...
In this review article, we have discussed the mechanism of hydrogen generation in InGaN nanowires via PEC water splitting and the range of reported InGaN ...
[58]
Indium clustering in a-plane InGaN quantum wells as evidenced by ...
Feb 18, 2015 · One surprising feature of InGaN QWs is that their light emission appears to be robust to the presence of threading dislocations with densities ...Missing: states review
[59]
Carrier localization in In-rich InGaN/GaN multiple quantum wells for ...
Mar 20, 2015 · In this paper, we report on a study of In-rich InGaN/GaN multiple quantum wells (MQWs) by using temperature dependent PL spectroscopy, near- ...
[60]
Selective Area Growth of InGaN/GaN Nanocolumnar ...
The aim of this work is to gain insight into the selective area growth (SAG) of InGaN nanostructures by plasma-assisted molecular beam epitaxy, ...
[61]
Dislocation Filtering in GaN Nanostructures | Nano Letters
Dislocation filtering in GaN by selective area growth through a nanoporous template is examined both by transmission electron microscopy and numerical modeling.
[62]
[PDF] Top-Down Etched Site-Controlled InGaN/GaN Quantum Dots
Due to the lower hole concentration and mobility in the p-GaN region, holes only start to arrive at the InGaN region at Vbias > 4 V. We note that hole injection ...
[63]
Single photon emission from InGaN/GaN quantum dots up to 50 K
Feb 9, 2012 · We have investigated the optical properties of single InGaN quantum dots (QDs) by means of microphotoluminescence (μPL) spectroscopy.
[64]
[PDF] High-density polarization-induced 2D electron gases in N-polar ...
Aug 25, 2022 · ABSTRACT. The polarization difference and band offset between Al(Ga)N and GaN induce two-dimensional (2D) free carriers in Al(Ga)N/GaN ...Missing: nanowires flexible displays biosensors
[65]
Flexible Light-Emitting Diodes Based on Vertical Nitride Nanowires
We demonstrate large area fully flexible blue LEDs based on core/shell InGaN/GaN nanowires grown by MOCVD.
[66]
Sensor applications based on AlGaN/GaN heterostructures
Aug 7, 2025 · In the case of AlGaN/GaN HEMT, the 2DEG is induced by piezoelectric polarization of the strained AlGaN layer together with spontaneous ...
[67]
[PDF] Procedures for Handling Indalloys (Liquid at Room Temperature)
Gallium may be absorbed through the skin. Rubber or vinyl gloves should be worn at all times when handling gallium- containing alloys. Contact an Indium ...Missing: safety nitride
[68]
[PDF] SAFETY DATA SHEET - Fisher Scientific
Mar 30, 2024 · Gallium(III) nitride may cause allergic skin reactions. Avoid breathing dust/fume/gas/mist/vapors/spray. Wear protective gloves. Wash skin with ...
[69]
[PDF] SAFETY DATA SHEET - Plasmaterials
The product may cause skin sensitization (Category 1). Avoid breathing dust, and wear protective gloves, clothing, eye and face protection. Wash thoroughly ...
[70]
Gallium Indium Alloy - ESPI Metals
Store in a cool, dry area away from metals. Do not store together with oxidizers, acids or halogens. See section 10 for more information on incompatible ...
[71]
[PDF] Handling of Indium-Contained Preforms
Wear safety glasses and gloves. Handle with care, as indium is soft. Avoid skin oils, use gloves or tweezers. Avoid inhaling fine powder.
[72]
[PDF] INDIUM CAS Number - NJ.gov
OSHA 1910.120(q) may be applicable. * Prior to working with Indium you should be trained on its proper handling and storage. * Indium must be stored to avoid ...
[73]
Recycling the GaN Waste from LED Industry by Pressurized ... - MDPI
This study will analyze the physical characteristics of LED wastes containing GaN and carry out various leaching methods to leach the valuable metals from the ...Missing: disposal | Show results with:disposal
[74]
Indium Consortium
The EU REACH Regulation entered into force on June 1 2007. REACH stands for Registration Evaluation and Authorization of CHemicals. REACH replaces the European ...
[75]
https://www.reach-indium.eu/