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Tell us your substrate and epi needs for GaN HEMT on silicon or related materials. Typical response time: 1 business day.
- Diameter (100–200 mm) and orientation (Si(111))
- Resistivity (HR or undoped), thickness
- Epi structure (Al% barrier, sheet R□, 2DEG density)
- Bow, warp, and TTV limits
Universities and labs worldwide use our substrates for HEMT, RF, and optoelectronic research.
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Quick Specs & Typical Values
- Substrate: Si(111), 100–200 mm (HR/undoped)
- Epi: AlGaN/GaN with AlN interlayer + graded buffer
- Sheet Resistance: ~350–420 Ω/□
- Mobility: ~1300–1800 cm²/V·s
- 2DEG Density: ~8×1012 – 1.2×1013 cm⁻²
- Bow: < 50 µm typical; TTV: < 10 µm
- Barrier: Al 25–30 nm (x ≈ 0.25–0.30)
FAQ
Why choose GaN-on-Si?
It offers large wafer sizes, lower cost, and compatibility with mainstream semiconductor fabrication.
For high-voltage devices, GaN-on-SiC remains optimal.
What should I include in my quote request?
Specify diameter, orientation, resistivity, target sheet R□ and 2DEG, buffer type, and bow/warp limits.
Do you supply sapphire and SiC substrates?
Yes, UniversityWafer offers sapphire
and Silicon Carbide (SiC)
for
GaN epitaxy and device prototyping.
What is a GaN HEMT on Silicon?
A Gallium Nitride High Electron Mobility Transistor (HEMT) uses an AlGaN/GaN heterojunction grown on a silicon substrate with carefully engineered buffer layers. At the interface between AlGaN and GaN, strong spontaneous and piezoelectric polarization effects generate a two-dimensional electron gas (2DEG) without intentional doping. This channel provides extremely high carrier mobility and sheet density, enabling devices with high current density, low on-resistance, and excellent high-frequency response.
Advantages of Using Silicon as the Substrate
- Large wafer diameters: Silicon substrates support 150 mm and 200 mm formats, allowing GaN HEMT fabrication in standard CMOS facilities.
- Lower cost: Silicon’s abundance and mature manufacturing reduce overall wafer cost compared with sapphire or SiC.
- Mechanical robustness: High fracture toughness makes wafer handling easier during epitaxy and dicing.
- CMOS compatibility: Enables integration of GaN power devices with silicon control circuitry on the same platform.
- Thermal conductivity: While lower than SiC, silicon still offers good thermal performance and established cooling techniques.
Challenges and Engineering Solutions
The large lattice (~17%) and thermal mismatch between GaN and Si can cause high dislocation densities and wafer bowing. To mitigate this, graded AlN/AlGaN buffer layers are grown to manage strain and minimize cracking. Advanced MOCVD or MBE growth techniques further optimize surface morphology, reduce leakage paths, and stabilize the 2DEG layer.
Typical AlGaN/GaN HEMT Epitaxial Stack Example
- GaN Cap (~2–3 nm)
- AlxGa1−xN barrier (~20–30 nm, x≈0.25–0.30)
- AlN interlayer (~1–2 nm)
- GaN channel (~1.5–2.0 µm)
- Graded AlGaN buffer (~1.0 µm)
- AlN nucleation layer on Si(111)
- Silicon substrate (100 or 111 orientation, 100–200 mm)
Typical parameters: 2DEG sheet density 8×1012–1.2×1013 cm⁻², mobility 1300–1800 cm²/V·s, and sheet resistance 350–420 Ω/□. Bow and TTV control are critical for lithographic yield and reliability.
How HEMTs Work
The 2DEG acts as the conductive channel between source and drain. When a negative gate voltage depletes this channel, current flow is modulated. Because no ionized dopants are present, scattering is reduced, allowing high electron velocity and low noise. These properties make HEMTs ideal for RF, radar, and high-efficiency power switching circuits.
Comparing GaN-on-Si vs. GaN-on-SiC vs. GaN-on-Sapphire
| Substrate | Thermal Conductivity (W/m·K) | Wafer Size (mm) | Cost | Typical Use |
|---|---|---|---|---|
| Silicon (Si) | ~150 | 100–200 | Low | Cost-effective R&D, CMOS-compatible RF and power |
| Silicon Carbide (SiC) | ~490 | 100–150 | High | High-power and high-voltage devices |
| Sapphire (Al2O3) | ~25 | 50–150 | Medium | Optoelectronic and LED devices |
Thermal Management in GaN-on-Si Devices
Although silicon has moderate thermal conductivity, managing self-heating in GaN HEMTs remains important. Backside thinning, heat spreaders, and diamond or AlN composite layers are often used to improve heat extraction. Research is ongoing into integrating microfluidic cooling for next-generation RF amplifiers.
Application Areas
- 5G/6G base stations and RF front-end modules
- Phased-array radar and satellite transceivers
- High-efficiency DC–DC converters and motor inverters
- Millimeter-wave imaging and sensing
- Microwave power amplifiers for industrial and medical systems
Available Research Substrates
- Undoped & high-resistivity silicon wafers — Si(111), 100–200 mm, for GaN epitaxy and test growth.
- Sapphire wafers — 2–6 inch, ideal for AlGaN/GaN HEMT epi and optical inspection.
- Silicon Carbide (SiC) — semi-insulating and conductive types for high-voltage GaN devices.
- Aluminum Nitride wafers — high thermal conductivity and lattice-matched alternatives for R&D.
Requesting a Quote
When contacting UniversityWafer, include:
- Diameter and orientation (typically Si(111))
- Resistivity and doping type (HR or undoped)
- Epi design parameters: barrier Al%, thickness, and buffer scheme
- Desired sheet resistance and 2DEG density range
- Wafer bow, warp, and surface finish requirements
Request a fast quote for silicon, sapphire, SiC, or AlN substrates suitable for AlGaN/GaN HEMT R&D, RF, and power device fabrication.