spore: profile
id: aluminium-gallium-nitride
spore_version: 0.2
family: nitride-semiconductors
name: Aluminium gallium nitride
abbreviation: AlGaN
role: wide-bandgap semiconductor alloy
category: semiconductors
type: gan
summary: |
  Aluminium gallium nitride (AlGaN) is an alloy of aluminium nitride and gallium nitride, written AlxGa1-xN. NASA gives the direct bandgaps of GaN and AlN as 3.4 eV and 6.2 eV, so the aluminium fraction x sets a bandgap anywhere between those two values. A 2006 trade article reports a back-illuminated AlGaN array from BAE Systems with a 280 nm solar-blind cut-off, using an Al0.47Ga0.53N absorber. NASA reports that AlGaN detectors can be designed to reject solar radiation about 1000 times better than silicon detectors at a 325 nm cut-off. No density or melting point for the alloy was found in the sources read for this profile. Calculated alloy values at x = 0.5 are listed: lattice constants (DFT), a first-principles thermal conductivity, and a bulk modulus from a machine-learning potential. These are calculations, not measurements.
best_for: Ultraviolet detectors that must ignore sunlight, such as solar-blind work below 280 nm (BAE Systems) and planetary UV instruments (NASA Goddard)
weakest_at: Few material constants for the alloy were found. The numbers here are mostly device results, and the cut-off figures differ between sources (see gaps)
identity:
  formula: AlxGa1-xN, an alloy of aluminium nitride (AlN) and gallium nitride (GaN); x is the aluminium fraction
  source: wiki-algan
  where: Lead section (formula AlxGa1-xN; alloy of AlN and GaN)
tags:
  applications:
    - optics-and-cameras
properties:
  - benchmark: bandgap
    label: Direct bandgap, GaN to AlN end members (alloy range)
    value: 3.4
    value_high: 6.2
    bound: range
    unit: eV
    scope: material
    conditions:
      composition: AlxGa1-xN from x = 0 (GaN) to x = 1 (AlN)
      temperature: not stated in the abstract
      basis: end-member values from the abstract; the bandgap at intermediate x is not given in this source
    method: Direct bandgaps printed in the NASA abstract for three nitrides, read as InN, GaN and AlN in that order; the 3.4 eV and 6.2 eV values are the GaN and AlN entries
    status: ground
    source: ntrs-2012
    where: Abstract, sentence giving direct bandgaps 0.8, 3.4 and 6.2 eV, respectively
  - benchmark: cutoff_wavelength
    label: Tunable detection range of AlGaN alloys
    value: 200
    value_high: 365
    bound: range
    unit: nm
    scope: material
    conditions:
      basis: tunable direct-bandgap range quoted for AlGaN alloys
      composition: AlGaN across the alloy range
    method: Range printed in a 2006 trade article on AlGaN filter-free detection; the NASA abstract gives 200 nm for AlN and 365 nm for GaN as the matching ends
    status: ground
    source: compoundsemi-2006
    where: Article text on the tunable direct bandgap (section not labelled in the fetched text)
  - benchmark: cutoff_wavelength
    label: Solar-blind cut-off of the AlGaN absorber
    value: 280
    unit: nm
    scope: material
    conditions:
      absorber: Al0.47Ga0.53N
      device: back-illuminated AlGaN hybrid focal-plane array developed at BAE Systems, Lexington, MA
      operation: solar-blind, below 280 nm
    method: Cut-off wavelength printed in the article for the absorber layer
    status: ground
    note: The NASA abstract gives 325 nm for its AlGaN design (see the 325 nm row below). Both figures are printed; this profile does not choose between them.
    source: compoundsemi-2006
    where: Article text on the Al0.47Ga0.53N absorber and solar-blind operation below 280 nm
  - benchmark: cut_on_wavelength
    label: Short-wavelength edge of the photosensitivity band
    value: 260
    unit: nm
    scope: material
    conditions:
      device: back-illuminated AlGaN hybrid focal-plane array (BAE Systems)
      band: 260 to 280 nm photosensitivity
    method: Cut-on wavelength printed in the article
    status: ground
    source: compoundsemi-2006
    where: Article text on the 260 to 280 nm photosensitivity band
  - benchmark: quantum_efficiency_peak
    label: Peak quantum efficiency at zero bias
    value: 48
    unit: '%'
    scope: material
    conditions:
      bias: zero bias
      device: AlGaN photodiode described in the article
      wavelength: not stated in the fetched article text
    method: Peak quantum efficiency printed in the article's detector performance paragraph
    status: ground
    source: compoundsemi-2006
    where: Article text, detector performance paragraph (48% peak quantum efficiency at zero bias)
  - benchmark: quantum_efficiency
    label: Quantum efficiency at 270 nm
    value: 50
    bound: lower
    unit: '%'
    scope: material
    conditions:
      wavelength: 270 nm
      device: solar-blind AlGaN array described in the article
    method: Printed as more than 50% at 270 nm in the article
    status: ground
    source: compoundsemi-2006
    where: Article text, detector performance paragraph (quantum efficiency of more than 50% at 270 nm)
  - benchmark: quantum_efficiency
    label: Quantum efficiency without reflection loss
    value: 52.3
    unit: '%'
    scope: material
    conditions:
      device: UT diode described in the article
      basis: figure the authors state would apply with no reflection loss
    method: Corrected figure stated by the article's authors; not a direct measurement in the source
    status: calculated
    source: compoundsemi-2006
    where: Article text, quantum efficiency paragraph (the UT diode quantum efficiency would have been 52.3%)
  - benchmark: solar_rejection_ratio
    label: Solar radiation rejection compared with silicon (NASA Tech Briefs)
    value: 1000
    unit: x
    scope: material
    conditions:
      reference: silicon-based detectors
      basis: stated for AlGaN UV detectors in the NASA Tech Briefs article
    method: Figure printed in the NASA Goddard Tech Briefs article dated October 1, 2010
    status: ground
    source: techbriefs-gsc15673
    where: Article body, AlGaN solar radiation rejection compared with silicon
  - benchmark: cutoff_wavelength
    label: Cut-off wavelength of an AlGaN UV detector design (planetary)
    value: 325
    unit: nm
    scope: material
    conditions:
      basis: cut-off named in the same sentence as the 1000x rejection figure
      reference: silicon-based detectors
    method: Cut-off printed in the NASA abstract
    status: ground
    note: Conflicts with the 280 nm solar-blind cut-off printed in the 2006 article. Both are kept; no source reconciles them.
    source: ntrs-2012
    where: Abstract, sentence on AlGaN UV rejection compared with Si-based detectors
  - benchmark: responsivity
    label: Current responsivity at 360 nm, 0 V
    value: 0.13
    unit: A/W
    scope: material
    conditions:
      wavelength: 360 nm
      bias: 0 V
      device: AlGaN UV PIN photodiode as described in the NASA Tech Briefs article
    method: Figure printed in the NASA Tech Briefs article
    status: ground
    note: The same article gives a 365 nm long-wavelength cut-off for this device, which matches the GaN value in the NASA abstract. The composition of this device is not stated, so it is not the 280 nm absorber.
    source: techbriefs-gsc15673
    where: Article body, performance figures for the AlGaN photodiode
  - benchmark: quantum_efficiency_peak
    label: Peak quantum efficiency at 360 nm, -0.5 V
    value: 50
    unit: '%'
    scope: material
    conditions:
      wavelength: 360 nm
      bias: '-0.5 V'
      device: same AlGaN photodiode as the 0.13 A/W responsivity row
    method: Figure printed in the NASA Tech Briefs article
    status: ground
    note: 'Same device caveat as the responsivity row: its cut-off is printed as 365 nm.'
    source: techbriefs-gsc15673
    where: Article body, performance figures for the AlGaN photodiode
  - benchmark: lattice_constant_a
    label: Lattice constant a, Al0.50Ga0.50N (DFT)
    value: 3.1719
    unit: Å
    scope: material
    conditions:
      composition: Al0.50Ga0.50N (x = 0.5)
      structure: wurtzite
      basis: density functional theory calculation in the paper, listed as Present Work
    method: DFT with the generalized gradient approximation (GGA) on the wurtzite cell, as stated in the paper's abstract
    status: calculated
    source: arxiv-lattice-0811
    where: Table I, Al0.50 Ga0.50 N row, a column
  - benchmark: lattice_constant_c
    label: Lattice constant c, Al0.50Ga0.50N (DFT)
    value: 5.1012
    unit: Å
    scope: material
    conditions:
      composition: Al0.50Ga0.50N (x = 0.5)
      structure: wurtzite
      basis: density functional theory calculation in the paper, listed as Present Work
    method: DFT with the generalized gradient approximation (GGA) on the wurtzite cell, as stated in the paper's abstract
    status: calculated
    source: arxiv-lattice-0811
    where: Table I, Al0.50 Ga0.50 N row, c column
  - benchmark: thermal_conductivity
    label: Thermal conductivity along [100], Al0.5Ga0.5N (first-principles)
    value: 186.74
    unit: W/(m·K)
    scope: material
    conditions:
      composition: Al0.5Ga0.5N
      direction: '[100]'
      temperature: 300 K
    method: First-principles calculation of anisotropic thermal conductivity, printed in the paper's abstract
    status: calculated
    source: mpm-thermal-2022
    where: Abstract, Al0.5Ga0.5N row of the thermal conductivity table, [100] column
  - benchmark: thermal_conductivity
    label: Thermal conductivity along [001], Al0.5Ga0.5N (first-principles)
    value: 165.24
    unit: W/(m·K)
    scope: material
    conditions:
      composition: Al0.5Ga0.5N
      direction: '[001]'
      temperature: 300 K
    method: First-principles calculation of anisotropic thermal conductivity, printed in the paper's abstract
    status: calculated
    source: mpm-thermal-2022
    where: Abstract, Al0.5Ga0.5N row of the thermal conductivity table, [001] column
  - benchmark: thermal_conductivity
    label: Thermal conductivity along [111], Al0.5Ga0.5N (first-principles)
    value: 177.62
    unit: W/(m·K)
    scope: material
    conditions:
      composition: Al0.5Ga0.5N
      direction: '[111]'
      temperature: 300 K
    method: First-principles calculation of anisotropic thermal conductivity, printed in the paper's abstract
    status: calculated
    source: mpm-thermal-2022
    where: Abstract, Al0.5Ga0.5N row of the thermal conductivity table, [111] column
  - benchmark: bulk_modulus
    label: Bulk modulus, Al0.5Ga0.5N (machine-learning potential)
    value: 204
    unit: GPa
    scope: material
    conditions:
      composition: Al0.5Ga0.5N (x = 0.5), wurtzite
      basis: prediction from a machine-learning interatomic potential, labelled This work in Table I
    method: Elastic constants and bulk modulus B from the machine-learning potential at the ground state, as printed in the paper
    status: calculated
    source: arxiv-elastic-2510
    where: Table I, Al0.5 Ga0.5 N row, B column
  - benchmark: frenkel_pair_formation_energy
    label: Lowest nitrogen Frenkel pair formation energy, AlGaN with 25% Al
    value: 6.57
    unit: eV
    scope: material
    conditions:
      composition: 25% Al (AlxGa1-xN, x = 0.25)
      defect: nitrogen Frenkel pair (a vacancy plus an interstitial), lowest-energy configuration in the energy histogram
    method: Machine-learning interatomic potential calculation, as stated in the paper's text; not an irradiation experiment
    status: calculated
    source: arxiv-elastic-2510
    where: Section B (Frenkel Pair Formation Energy), paragraph on the 25% Al energy histogram
corrosion: []
risks:
  hazards:
    - text: 'PubChem GHS for gallium nitride, the GaN end member (not AlGaN itself): H317, May cause an allergic skin reaction, with signal word Warning, reported in 97.8% of aggregated company notifications. 2.2% of reports say the chemical does not meet GHS hazard criteria.'
      ghs:
        - H317
      source: pubchem-gan
      where: Safety and Hazards, Hazards Identification, GHS Classification (CID 117559)
  failure_risks:
    - mode: Nitrogen Frenkel pair defects in AlGaN under radiation or high temperature
      trigger: Irradiation or high-temperature processing (calculated only; the paper does not test irradiation)
      consequence: The paper calculates that low-energy nitrogen Frenkel pairs exist in AlGaN, with the lowest at 6.57 eV at 25% Al, and states that under irradiation or high-temperature processing these configurations may form preferentially and dominate the early defect population.
      source: arxiv-elastic-2510
      where: Section B, Frenkel pair formation energy, and the implications paragraph
  side_effects: []
  handling: []
  mitigations: []
uses:
  - application: optics-and-cameras
    device: Back-illuminated solar-blind UV focal-plane array (256 x 256 pixels)
    example: The 2006 article describes BAE Systems' first solar-blind 256 x 256 AlGaN back-illuminated hybrid UV focal-plane arrays, with 30 um x 30 um unit cells and photosensitivity in the 260 to 280 nm band.
    source: compoundsemi-2006
    where: Article text on the 256 x 256 array and unit cells
  - application: optics-and-cameras
    device: UV detector for planetary missions
    example: NASA Goddard's abstract, titled for next-generation ultraviolet planetary missions, says AlGaN detectors can be designed to give 1000x solar radiation rejection at a 325 nm cut-off, compared with Si-based detectors.
    source: ntrs-2012
    where: Title and abstract
  - application: optics-and-cameras
    device: UV sensing instruments for plume, flame, lidar and bio-agent work
    example: The NASA Tech Briefs article lists AlGaN UV detector uses as plume measurements, flame sensing, UV lidar, biological agent detection, and airborne particulate size and velocity measurement.
    source: techbriefs-gsc15673
    where: Article body, applications paragraph
supply:
  - subject: Gallium
    producers:
      - country: China
        share_percent: 99
        year: 2025
    critical_lists:
      - list: 'USGS 2025 List of Critical Minerals (entry: Gallium, used in semiconductors)'
        listed: true
      - list: 'EU critical raw materials list (Regulation (EU) 2024/1252, entry: Gallium)'
        listed: true
    recycling: 'USGS: old scrap recovery is none. Substantial new scrap from GaAs device manufacture was reprocessed to high-purity gallium at one New York facility.'
    substitutes:
      - 'USGS: in many defense-related applications no effective substitutes exist for GaAs and GaN.'
    source: usgs-mcs2026-gallium
    where: Events, Trends, and Issues (China accounted for 99% of worldwide primary low-purity gallium production); Recycling; Substitutes; Salient Statistics table (net import reliance 100 in every year listed). The 99% is for primary low-purity gallium, not for refined gallium used in AlGaN.
  - subject: 'Aluminium (USGS spelling: aluminum)'
    producers:
      - country: China
        share_percent: 60.8
        year: 2025
      - country: India
        share_percent: 5.7
        year: 2025
      - country: Russia
        share_percent: 5.3
        year: 2025
      - country: Canada
        share_percent: 4.5
        year: 2025
    critical_lists:
      - list: 'USGS 2025 List of Critical Minerals (entry: Aluminum, used in almost all sectors of the economy)'
        listed: true
      - list: EU critical raw materials list (aluminium merged into the Bauxite entry, per the European Commission page)
        listed: true
    recycling: 'USGS: about 3.6 million tons of aluminum were recovered from purchased scrap in the United States in 2025.'
    substitutes: []
    source: usgs-mcs2026-aluminum
    where: World smelter production table, 2025e (shares calculated by Space Mushroom from China 45,000, India 4,200, Russia 3,900 and Canada 3,300 against the printed world total of 74,000, rounded); Recycling. Aluminium is the feedstock for the aluminium part of the alloy.
documents:
  - title: 'NASA NTRS 20120016988: GaN-Based Detector Enabling Technology for Next Generation Ultraviolet Planetary Missions'
    type: report
    url: https://ntrs.nasa.gov/citations/20120016988
    year: 2012
  - title: 'USGS Mineral Commodity Summaries 2026: Gallium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-gallium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Aluminum'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
    year: 2026
  - title: NASA Tech Briefs article, reference GSC-15673-1
    type: report
    url: https://www.techbriefs.com/component/content/article/8640-gsc-15673-1
    year: 2010
  - title: 'arXiv 0811.0380: Ab initio calculation of structural and electronic properties of AlxGa1-xN and InxGa1-xN alloys'
    type: paper
    url: https://arxiv.org/pdf/0811.0380
    year: 2008
  - title: 'arXiv 2510.25912: Evaluation of Structural Properties and Defect Energetics in AlxGa1-xN Alloys'
    type: paper
    url: https://arxiv.org/pdf/2510.25912
    year: 2025
  - title: 'Materials Physics and Mechanics 49(1): First-principles study of anisotropic thermal conductivity of GaN, AlN, and Al0.5Ga0.5N'
    type: paper
    url: https://mpm.spbstu.ru/article/2022.89.7/
    year: 2022
  - title: 'PubChem CID 117559: Gallium nitride, GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Gallium-nitride
    year: 2026
gaps:
  - Density, melting or decomposition temperature, electron mobility and breakdown field for AlGaN were not found in any source read in this run. The lattice constants, thermal conductivity and bulk modulus in the properties list are calculated values at x = 0.5, not measurements. The arXiv 0811.0380 table also gives lattice constants at x = 0.25 and 0.75, which are not added.
  - The Ioffe Institute basic-parameter page for AlGaN could not be opened in this run (self-signed certificate error), so its band-gap bowing and thermal values are not used. The Springer and Balandin group AlGaN pages and a DOAJ record for a 270 nm AlGaN LED irradiation paper could not be opened either (redirect, DNS failure and a Cloudflare block).
  - No safety data sheet or GHS entry for AlGaN itself was found. The hazard entry is for the GaN end member from PubChem. The Wikipedia safety note (toxicology not fully studied; dust irritates skin, eyes and lungs) was not used as a source because the brief limits Wikipedia to composition and history. A supplier SDS for AlGaN wafers or powder is needed.
  - No corrosion, oxidation, ageing or humidity test for AlGaN was read, so the corrosion list is empty.
  - The one failure entry is a calculated defect energy from a machine-learning potential. No irradiation test or device-level failure data for AlGaN was read. The source gives no severity, so the failure entry has no severity field.
  - Lattice constants a and c and the frenkel_pair_formation_energy benchmark are short snake_case names not in spores/property-canon.yaml. Elastic constants C11, C12, C13, C33 and C44 for Al0.5Ga0.5N (2510.25912 Table I) are not added, only the bulk modulus B.
  - AlGaN/GaN high-electron-mobility transistor use is named only in Wikipedia. No HEMT property (mobility, carrier density, power or frequency) was read.
  - The 280 nm solar-blind cut-off (2006 article) and the 325 nm cut-off (NASA abstract) are both printed. No source reconciles them.
  - The 48% peak quantum efficiency is printed without a wavelength in the fetched article text.
  - The NASA Tech Briefs device is called AlGaN but has a 365 nm cut-off, and its composition is not stated. Its responsivity and quantum efficiency rows are kept with that caveat.
  - No atomic weight for aluminium, gallium or nitrogen was read in a fetched source, so the recipe parts carry no atomic weights.
  - No standard designation (UNS, EN, CAS) exists for the alloy in any source read; AlGaN is a composition family, not one grade.
  - Crustal abundance of gallium and aluminium was not read in this run.
  - Benchmark names cutoff_wavelength, cut_on_wavelength, quantum_efficiency, quantum_efficiency_peak, responsivity and solar_rejection_ratio are short snake_case names. None is in spores/property-canon.yaml, and bandgap is used as in the GaN profile.
  - The 99% gallium share is a USGS statement about primary low-purity production. The aluminium shares are calculated by Space Mushroom from smelter production, not taken from a printed share.  - "The NASA abstract's 1000x rejection figure is read from the fetched summary. The PDF text layer prints it as I OOOx (OCR), so the value check could not match it and the figure has no verified property row. The NASA Tech Briefs row with the same figure could not be read by the value check either."
sources:
  ntrs-2012:
    title: GaN-Based Detector Enabling Technology for Next Generation Ultraviolet Planetary Missions
    id: NTRS 20120016988; GSFC.CPR.6772.2012; IPM-2012 (October 10, 2012)
    url: https://ntrs.nasa.gov/citations/20120016988
    year: 2012
    kind: report
    license: public domain (NASA)
  compoundsemi-2006:
    title: AlGaN provides filter-free detection (Compound Semiconductor, article 84128)
    id: Compound Semiconductor, published 27 June 2006
    url: https://compoundsemiconductor.net/article/84128/AlGaN_provides_filter-free_detection
    year: 2006
    kind: web
    license: trade article, cited not reproduced
  techbriefs-gsc15673:
    title: NASA Tech Briefs article, reference GSC-15673-1 (AlGaN solar-blind UV detector)
    id: GSC-15673-1; NASA Tech Briefs Vol. 34 No. 10 (October 1, 2010)
    url: https://www.techbriefs.com/component/content/article/8640-gsc-15673-1
    year: 2010
    kind: web
    license: public domain (NASA text)
  wiki-algan:
    title: Aluminium gallium nitride (Wikipedia), used for composition only
    id: Wikipedia, lead section
    url: https://en.wikipedia.org/wiki/Aluminium_gallium_nitride
    year: 2026
    kind: web
    license: CC BY-SA 4.0
  usgs-mcs2026-gallium:
    title: Mineral Commodity Summaries 2026, Gallium
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-gallium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-aluminum:
    title: Mineral Commodity Summaries 2026, Aluminum
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS, final list of 60 minerals)
    id: Final 2025 List of Critical Minerals
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, Regulation (EU) 2024/1252)
    id: Regulation (EU) 2024/1252
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
  arxiv-lattice-0811:
    title: Ab initio calculation of structural and electronic properties of AlxGa1-xN and InxGa1-xN alloys
    id: arXiv:0811.0380; E. López-Apreza, J. Arriaga and D. Olguín (2008)
    url: https://arxiv.org/pdf/0811.0380
    year: 2008
    kind: paper
    license: arXiv preprint
  arxiv-elastic-2510:
    title: Evaluation of Structural Properties and Defect Energetics in AlxGa1-xN Alloys
    id: arXiv:2510.25912; F. Reza, B. Chen and M. Jin (Pennsylvania State University, 2025)
    url: https://arxiv.org/pdf/2510.25912
    year: 2025
    kind: paper
    license: arXiv preprint
  mpm-thermal-2022:
    title: First-principles study of anisotropic thermal conductivity of GaN, AlN, and Al0.5Ga0.5N
    id: Materials Physics and Mechanics 49(1), pp. 97-107; D. Hvazdouski, M.S. Baranava and V.R. Stempitsky (2022)
    url: https://mpm.spbstu.ru/article/2022.89.7/
    year: 2022
    kind: paper
    license: not checked
  pubchem-gan:
    title: Gallium nitride, PubChem CID 117559, GHS classification
    id: PubChem CID 117559 (Gallium nitride)
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Gallium-nitride
    year: 2026
    kind: database
    license: PubChem public database
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 18
  unreachable: 4
  caveats: 3
  note: Written by an AI assistant on 2026-11-01 from the NASA, trade, alloy-calculation and USGS pages, and deepened the same day with arXiv tables, an MPM first-principles paper and PubChem GHS data. Values are copied as printed. The Ioffe AlGaN page, the Springer and Balandin pages and a DOAJ record could not be opened. The NASA full text was read from a fetch summary.
story:
  recipe:
    line: AlGaN is an alloy of aluminium nitride (AlN) and gallium nitride (GaN), written AlxGa1-xN. The aluminium fraction x sets the bandgap. The 2006 article says the detector layers were grown on 2 inch c-plane sapphire substrates.
    parts:
      - name: Aluminium
        symbol: Al
        share_of_metal_sites: x
        role: Sets the bandgap. The NASA abstract gives 6.2 eV for pure AlN, the wide end of the alloy range.
      - name: Gallium
        symbol: Ga
        share_of_metal_sites: 1 - x
        role: Sets the bandgap. The NASA abstract gives 3.4 eV for pure GaN, the narrow end of the alloy range.
      - name: Nitrogen
        symbol: 'N'
        role: Bonds to the metal atoms in the nitride lattice. The sources read give no further detail.
  risk_groups:
    - title: For people
      verdict: GaN end member carries H317 (may cause an allergic skin…
      lead: No safety data sheet or GHS entry for AlGaN itself was read. PubChem's GHS entry for the GaN end member gives H317, a skin sensitiser warning.
      points:
        - label: Dust
          line: Handle wafers and powder with care until a supplier safety data sheet for the specific product has been checked.
        - label: Skin contact
          line: PubChem's aggregated GHS entry for gallium nitride lists H317, may cause an allergic skin reaction, and signal word Warning.
  why: Aluminium gallium nitride (AlGaN) is a semiconductor that can be tuned across the ultraviolet. NASA gives direct bandgaps of 3.4 eV for GaN and 6.2 eV for AlN, and the aluminium fraction sets the value in between. A detector that absorbs only below a chosen wavelength can ignore the visible and near-visible light of the Sun. NASA Goddard works on this family of detectors for next-generation ultraviolet planetary missions.
  uses:
    - where: Solar-blind ultraviolet focal-plane arrays
      line: A 2006 article describes BAE Systems' 256 x 256 back-illuminated AlGaN hybrid arrays, with an absorber that cuts off at 280 nm and a photosensitivity band of 260 to 280 nm.
    - where: Planetary ultraviolet detectors
      line: NASA's abstract says AlGaN detectors can be designed to reject solar radiation 1000 times better than silicon detectors at a 325 nm cut-off.
    - where: UV sensing instruments
      line: A NASA Tech Briefs article lists plume measurements, flame sensing, UV lidar, biological agent detection and airborne particle sizing as uses of AlGaN UV detectors.
  can_do:
    - label: Bandgap tuning
      benchmark: bandgap
      value: 3.4 to 6.2 eV
      line: The NASA abstract gives direct bandgaps of 3.4 eV for GaN and 6.2 eV for AlN, the two ends of the alloy range. The bandgap of the alloy at a given aluminium fraction is not printed in the sources read.
    - label: Solar-blind cut-off
      benchmark: cutoff_wavelength
      value: 280 nm
      line: The 2006 article says an Al0.47Ga0.53N absorber gives a 280 nm cut-off, and that the array operates below 280 nm, the solar-blind band.
    - label: Solar rejection
      benchmark: solar_rejection_ratio
      value: 1000x
      line: NASA gives 1000 times better solar rejection than silicon detectors at a 325 nm cut-off, and a NASA Tech Briefs article repeats the 1000x figure.
    - label: Quantum efficiency
      benchmark: quantum_efficiency_peak
      value: 48%
      line: The 2006 article gives a 48% peak quantum efficiency at zero bias for an AlGaN photodiode, and more than 50% at 270 nm.
  compare: 'AlGaN covers a tunable part of the ultraviolet that GaN alone cannot, because the aluminium fraction moves the bandgap from the 365 nm GaN cut-off down toward the 200 nm AlN end (NASA abstract). Silicon is the reference for solar rejection: NASA gives 1000 times better rejection for AlGaN than silicon at a 325 nm cut-off. The sources read give no density or mobility for the alloy. The thermal conductivity and lattice values at x = 0.5 are first-principles calculations, so they are not ranked against measured values for other materials.'
  compare_rows:
    - label: Bandgap across the alloy range
      benchmark: bandgap
    - label: Solar-blind cut-off
      benchmark: cutoff_wavelength
    - label: Quantum efficiency at peak
      benchmark: quantum_efficiency_peak
  handling:
    - No handling data for AlGaN were found in the sources read this run. Use the supplier safety data sheet for the wafer or powder you buy.
    - Keep the wafer or powder dry and closed until use, and avoid dust, pending a product SDS.
  good_for:
    - Solar-blind ultraviolet detection, where the 2006 article reports operation below 280 nm.
    - Planetary ultraviolet instruments, where NASA reports 1000 times better solar rejection than silicon.
  watch_out:
    - 'Sources disagree on the cut-off: 280 nm for the 2006 BAE Systems absorber and 325 nm for the NASA design. Both are printed.'
    - The NASA Tech Briefs photodiode has a 365 nm cut-off, which matches GaN, so its numbers are for a different design.
    - No density, melting point, mobility or breakdown field for the alloy was found in any source read this run. The thermal conductivity and bulk modulus rows are first-principles or machine-learning calculations, not measurements.
    - 'The one failure entry is calculated, not tested: a nitrogen Frenkel pair energy from the machine-learning study, with no irradiation test on AlGaN read.'
  verdict: AlGaN is a tunable ultraviolet semiconductor whose bandgap range is documented at its two ends, 3.4 eV for GaN and 6.2 eV for AlN. The device numbers are results from detectors, and the alloy constants are calculated at x = 0.5, so the material data are still thin, with no measured density, melting point or mobility for the alloy found yet.