III-V Infrared & Quantum Materials
Gallium Antimonide (GaSb) Wafer & T2SL Infrared Lab
Explore stoichiometric Vertical Gradient Freeze (VGF) crystal growth at 712°C, 6N Ga and 6N Sb precursors, low-EPD substrate polishing, broken-gap InAs/GaSb Type-II superlattice (T2SL) bandgap engineering, and 20-year DCF cleanroom fab economics for next-generation MWIR/LWIR defense sensors and High Operating Temperature (HOT 150K) thermal imaging.
Annual Epi-Ready Wafers
18,920
Substrate: 22.0 g (100mm)
FPA Sensors/Yr
624.4k
Levelized Wafer Cost
$520 / wafer
Annual Revenue
$25.5M
Epi-ready substrates
Annual EBITDA
$15.7M
61.5% margin
20-Yr NPV (8.5%)
$64.2M
Discounted FCF
Project IRR
21.8% IRR
4.6 Years
6N Ga Precursor
$13.3 / wafer
36.4% mass fraction
6N Sb Feedstock
$2.4 / wafer
63.6% mass fractionGaSb VGF Crystal Growth & Type-II Superlattice Architecture
VGF Crystal Growth & Cleanroom Fab Parameters
GaSb & Type-II Superlattice Physics
1. The 6.1 Å Family Lattice Matching
GaSb ($6.0959\text{ \AA}$) provides near-zero lattice strain for InAs ($6.0584\text{ \AA}$) and AlSb ($6.1355\text{ \AA}$):
$\Delta a / a = \frac{a_{\text{InAs}} - a_{\text{GaSb}}}{a_{\text{GaSb}}} \approx -0.61\%$
Allows strain-balanced superlattice growth of over 500 periods without generating misfit dislocations.
2. Broken-Gap Type-II Band Engineering
The conduction band of InAs lies below the valence band of GaSb ($\Delta E_v \approx 0.51\text{ eV}$):
$E_{g,\text{eff}} = E_c(\text{InAs}) - E_v(\text{GaSb}) + \Delta E_{\text{quantum}} \implies \lambda_c = \frac{hc}{E_{g,\text{eff}}}$
Enables continuously tunable infrared absorption across MWIR (3-5 µm) and LWIR (8-12 µm).
3. High Operating Temperature (HOT) SWaP-C
Higher effective electron mass ($m_e^* \approx 0.03\text{ }m_0$) suppresses tunneling dark current:
$J_{\text{dark}} \propto \exp\left(-\frac{\sqrt{m_e^*} \cdot E_g^{3/2}}{\hbar q \mathcal{E}}\right) \implies T_{\text{op}} = 150\text{ K}$
Replaces bulky liquid-nitrogen 77K cryocoolers with miniature 150K Stirling coolers.
4. Crystal Stoichiometry & Density
GaSb crystallizes in the zinc-blende ($F\bar{4}3m$) structure with density $\rho = 5.614\text{ g/cm}^3$:
$\text{Mass}(100\text{mm}) \approx 22.0\text{ g} \quad (36.4\%\text{ Ga}, \, 63.6\%\text{ Sb})$
20-Year DCF Cash Flow Schedule ($M USD)
Cleanroom Foundry Model| Period | Revenue | Operating Costs | EBITDA | Free Cash Flow | Discounted FCF | Cumulative Cash |
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GaSb Substrates & T2SL Physics Knowledge Check
Frequently Asked Questions (FAQ)
GaSb has a lattice constant of 6.0959 Å, which forms the anchor of the renowned '6.1 Å III-V semiconductor family' alongside InAs (6.0584 Å) and AlSb (6.1355 Å). This extraordinary lattice matching (mismatch under 0.6%) enables the epitaxy of hundreds of atomic periods of alternating InAs and GaSb layers without generating lattice strain-induced misfit dislocations, which would otherwise act as non-radiative recombination centers and ruin infrared detector sensitivity.
In a Type-II broken-gap heterojunction, the conduction band edge of InAs lies approximately 0.15 eV lower than the valence band edge of GaSb. Electrons are energetically confined in the ultra-thin InAs quantum wells, while holes are confined in adjacent GaSb quantum wells. By tuning the sub-nanometer thickness of each layer (typically 1.5 to 4.5 nm), the effective miniature bandgap created by overlapping wavefunctions can be custom engineered to detect any infrared photon wavelength from 3 µm (MWIR) to 15 µm (VLWIR).
Mercury Cadmium Telluride (Hg1-xCdxTe) suffers from extreme compositional sensitivity (a 0.1% change in Cd fraction shifts the cutoff wavelength drastically), weak Hg-Te bonds leading to crystal defects, and an ultra-light electron effective mass (0.009 m0) that causes massive tunneling dark current unless cooled to 77K. T2SL offers superior spatial pixel uniformity across large wafers, robust covalent III-V bonding, and a larger electron effective mass (0.03 m0) that suppresses tunneling, allowing sensors to run at High Operating Temperatures (HOT, 150K), cutting cryocooler electrical power and payload weight by over 60%.
GaSb has relatively low mechanical yield strength at high temperatures. In conventional Czochralski pulling, high convective liquid turbulence and sharp axial temperature gradients create heavy thermal shear stress, generating high dislocation densities (EPD > 10,000 cm^-2). VGF grows the single crystal inside a stationary pyrolytic boron nitride (PBN) crucible by slowly translating a low temperature gradient through a multi-zone furnace. This quiescent growth reduces EPD below 500 cm^-2, providing the defect-free surface essential for growing complex superlattices.
A commercial GaSb wafer fabrication cleanroom requires between $60M and $180M in CapEx for high-pressure VGF synthesis furnaces, multi-wire diamond slicing saws, double-sided CMP polishers, and atomic force surface metrology. Epi-ready 100mm (4-inch) wafers command $1,000 to $1,800 each, while 150mm (6-inch) wafers sell for $1,500 to $2,500+. With 6N Gallium and Antimony feedstock costs comprising under 15% of total wafer value, gross margins typically exceed 60% and EBITDA margins remain above 50% across defense and aerospace procurement cycles.