Gallium Nitride on Sapphire (GaN-on-Sapphire) Substrates
GaN-on-Sapphire epitaxial substrates for LED, power electronics, and RF applications. Available in 2″ to 8″ diameters with C-plane sapphire base and high-quality GaN epi layers.
Gallium Nitride on Sapphire (GaN-on-Sapphire) Substrates
Gallium Nitride on Sapphire (GaN-on-Sapphire) is the foundational epitaxial substrate platform for the global solid-state lighting industry and is rapidly expanding into power electronics and RF applications. GaN's wide direct bandgap of 3.4 eV, high critical electric field (3.3 MV/cm), and the spontaneous formation of a high-mobility two-dimensional electron gas (2DEG) at AlGaN/GaN heterointerfaces make it the most versatile wide-bandgap semiconductor commercially available.
Because bulk GaN substrates remain expensive and limited in diameter, heteroepitaxial growth on sapphire (α-Al₂O₃) has become the dominant commercial approach. Sapphire offers a hexagonal crystal structure compatible with wurtzite GaN, outstanding thermal and chemical stability at MOCVD growth temperatures (1,000–1,100°C), transparency across the visible and near-UV spectrum (critical for LED light extraction), and availability in large diameters up to 8″ at moderate cost. The 16% lattice mismatch is managed through optimized low-temperature buffer layers (AlN or GaN) that nucleate high-quality GaN growth.
The GaN-on-Sapphire substrate market exceeds USD 800 million annually, driven primarily by LED production (over 100 billion die per year), with power electronics and RF representing the fastest-growing segments. The transition from 4″ to 6″ and 8″ sapphire substrates in LED fabs has driven a 3× reduction in cost per lumen over the past decade, making LED lighting the dominant illumination technology worldwide.
At GINECHIP, we supply GaN-on-Sapphire epitaxial substrates in UID, N-type Si-doped, and P-type Mg-doped variants from 2″ to 8″ diameters. Standard GaN epi thicknesses from 2μm to 8μm, with AlN buffer layer included in all templates. Premium-grade substrates with XRD (0002) FWHM below 200 arcsec and dislocation density below 1×10⁸/cm² are available for laser diode and high-reliability applications.
Epitaxial Growth Methods
Three distinct epitaxial growth approaches deliver GaN-on-Sapphire substrates, each optimized for different defect density, thickness, and cost requirements. MOCVD dominates volume production, while HVPE and ELOG serve high-value specialty applications.
MOCVD on Sapphire
TMGa + NH₃ precursors — highest throughput
Metal-Organic Chemical Vapor Deposition (MOCVD) is the dominant production method for GaN-on-Sapphire epitaxial substrates. Trimethylgallium (TMGa) and ammonia (NH₃) precursors are introduced into a heated reactor (1,000–1,100°C) where they pyrolyze and deposit GaN onto a C-plane sapphire wafer. A thin AlN or low-temperature GaN buffer layer nucleates the growth, managing the 16% lattice mismatch between GaN and sapphire. MOCVD enables precise thickness control (±5%), uniform doping, and high throughput for 2″ through 8″ wafers. This is the standard template for blue/green LED production worldwide.
HVPE Templates
GaCl + NH₃ chemistry — thick layers
Hydride Vapor Phase Epitaxy (HVPE) uses GaCl (formed by HCl gas flowing over liquid gallium) and NH₃ to deposit GaN at growth rates exceeding 100μm/hour — over 50× faster than MOCVD. HVPE is primarily used to grow thick (10–300μm) GaN layers that serve as quasi-bulk templates. These templates are subsequently separated from the sapphire substrate via laser lift-off or chemical etching to create free-standing GaN wafers, or kept as low-defect-density templates for high-voltage vertical power devices where thick drift layers are required.
ELOG (Epitaxial Lateral Overgrowth)
Patterned mask regrowth — lowest defect density
Epitaxial Lateral Overgrowth (ELOG) is a defect-reduction technique where a patterned dielectric mask (SiO₂ or SiNₓ) is deposited on a GaN template layer. During subsequent MOCVD regrowth, GaN nucleates selectively in mask openings and then grows laterally over the mask, bending and annihilating threading dislocations. The regions above the mask achieve dislocation densities below 5×10⁶/cm² — two orders of magnitude improvement over standard MOCVD GaN. ELOG substrates are essential for laser diodes where dislocation density directly determines device lifetime and threshold current density.
Growth Method Comparison: MOCVD vs HVPE vs ELOG
The choice between MOCVD, HVPE, and ELOG depends on the target device's defect tolerance, required GaN thickness, and economics. The table below summarizes key differentiating factors.
MOCVD on Sapphire
High-throughput metal-organic CVD producing GaN templates from 2″ to 8″. Threading dislocation density < 5×10⁸/cm² is acceptable for LED and power HEMT applications. The workhorse of the LED industry — over 95% of all GaN LEDs are produced on MOCVD-grown GaN-on-Sapphire.
HVPE Templates
Ultra-fast growth (50–200 μm/hr) producing thick GaN layers for quasi-bulk templates. Dislocation density below 1×10⁷/cm² — one order of magnitude better than MOCVD. Used for vertical power devices requiring thick drift layers and as precursors for free-standing GaN substrates after sapphire removal.
ELOG Regrowth
Patterned mask and lateral overgrowth reducing dislocation density to < 5×10⁶/cm² — two orders of magnitude below standard MOCVD. Essential for laser diodes where dislocation density directly correlates with device lifetime. Multi-step process with higher cost; reserved for premium applications.
Wide Bandgap Material Property Comparison
GaN's material properties place it at the intersection of high-frequency (GaAs domain) and high-power (SiC domain) performance. The table below compares key semiconductor figures of merit — Johnson (JFOM) for RF power capability and Baliga (BFOM) for DC-DC converter efficiency — across the four most important semiconductor materials in modern electronics.
| Property | GaN | Silicon (Si) | GaAs | 4H-SiC |
|---|---|---|---|---|
| Bandgap (eV) | 3.4 (direct) | 1.12 (indirect) | 1.42 (direct) | 3.26 (indirect) |
| Critical Field (MV/cm) | 3.3 | 0.3 | 0.4 | 2.8 |
| Electron Mobility (cm²/V·s) | 2,000 (2DEG) | 1,350 | 8,500 | 900 |
| Saturation Velocity (10⁷ cm/s) | 2.5 | 1.0 | 1.2 | 2.0 |
| Thermal Conductivity (W/m·K) | 130 (bulk) / 250 (SiC) | 150 | 55 | 490 |
| Max Operating Temp (°C) | > 500 | 150 | 200 | > 600 |
| JFOM (Johnson Figure of Merit) | 760 | 1 | 3 | 280 |
| BFOM (Baliga FOM, relative) | 650 | 1 | 15 | 130 |
Power Electronics: GaN HEMT Revolution
AlGaN/GaN HEMTs represent the most disruptive wide-bandgap device technology in power electronics. The spontaneous and piezoelectric polarization fields at the AlGaN/GaN heterointerface induce a 2DEG with sheet carrier concentrations exceeding 1×10¹³/cm² and electron mobility above 2,000 cm²/V·s — without the need for impurity doping. This creates a normally-on (depletion-mode) channel with exceptionally low sheet resistance (300–800 Ω/sq).
GaN power HEMTs achieve breakdown voltages from 100V to 1,200V with specific on-resistance (RDS(on)·A) 5–10× lower than the silicon theoretical limit. A 650V GaN HEMT in a 5×6mm PQFN package replaces a silicon super-junction MOSFET in a 10×12mm package while reducing gate charge (Qg) by 80% and output capacitance (Coss) by 70% — enabling hard-switching converters at 1 MHz+ with efficiencies exceeding 98%. This is transformative for USB-C fast chargers (65W in a 30cm³ volume), telecom rectifiers (3kW in 1U), and EV traction inverters where GaN is projected to reduce inverter losses by 50% compared to Si IGBTs.
GINECHIP offers AlGaN/GaN HEMT epiwafers on 6″ and 8″ sapphire with specified 2DEG sheet resistance (300–500 Ω/sq), carrier concentration (> 8×10¹²/cm²), and mobility (> 1,800 cm²/V·s). AlN interlayers and carbon-doping for dynamic RDS(on) suppression are available for power-switching applications.
Technical Specifications
| Parameter | Available Range / Values |
|---|---|
| Base Substrate | C-plane sapphire (0001), 430μm or 650μm thickness |
| GaN Epi Thickness | 2μm, 3.5μm, 5μm, 8μm (custom on request) |
| Doping Options | UID (unintentionally doped), N-type Si-doped, P-type Mg-doped |
| Dislocation Density | < 5×10⁸/cm² (typical); < 1×10⁸/cm² (premium grade) |
| Sheet Resistance | N-type: 300–800 Ω/sq; UID: > 10⁶ Ω/sq |
| Surface Roughness | Ra < 0.5nm (AFM 5×5μm scan) |
| Wafer Bow | ≤ 40μm (4″); ≤ 80μm (6″); ≤ 120μm (8″) |
| Available Diameters | 2″ (50.8mm), 4″ (100mm), 6″ (150mm), 8″ (200mm) |
| AlN Buffer Layer | 20–30nm, included in all standard templates |
| XRD FWHM (0002) | < 300 arcsec (typical); < 200 arcsec (premium) |
| XRD FWHM (10-12) | < 500 arcsec (typical); < 350 arcsec (premium) |
| GaN Bandgap | 3.4 eV (direct, wurtzite crystal structure) |
| Sapphire Thermal Expansion | 7.5×10⁻⁶/K (a-axis); 8.5×10⁻⁶/K (c-axis) at 300K |
| Sapphire Refractive Index | nₒ = 1.768, nₑ = 1.760 at 633nm |
| Backside Finish | As-cut, lapped, or polished per customer specification |
| Laser Mark | SEMI M12/M13 compliant: soft-mark on front or back side |
| Particle Count @ 0.3μm | ≤ 20 particles (laser surface scan) |
| Packaging | Vacuum-sealed single-wafer containers, Class 100 cleanroom |
| Compliance | SEMI Standards, RoHS, REACH |
Applications & Market Segments
Blue, Green & UV LEDs
GaN-on-Sapphire is the universal platform for InGaN/GaN multiple-quantum-well (MQW) LEDs spanning 365nm (UVA) to 550nm (green). The technology powers solid-state lighting, automotive headlamps, full-color displays (microLED), and UV-C sterilization. Over 100 billion GaN LEDs are produced annually on sapphire substrates — making this the highest-volume compound semiconductor application by unit count.
GaN Power HEMTs
AlGaN/GaN high-electron-mobility transistors (HEMTs) on silicon or sapphire substrates leverage the spontaneous and piezoelectric polarization-induced 2DEG (two-dimensional electron gas) with sheet carrier densities exceeding 1×10¹³/cm². GaN HEMTs achieve breakdown voltages above 650V with RDS(on) below 50mΩ, enabling compact, high-efficiency power supplies, EV onboard chargers, and data center PSUs that outperform silicon super-junction MOSFETs.
Laser Diodes (LDs)
GaN-based edge-emitting laser diodes operating at 405nm (violet/Blu-ray), 450nm (blue), and 520nm (green) require ELOG-quality substrates with dislocation density below 5×10⁶/cm². Applications include laser projection (pico-projectors, AR/VR waveguide displays), automotive LiDAR (scanning MEMS-mirror systems), and high-brightness laser lighting for stadium and architectural illumination.
GaN RF Transistors
GaN-on-SiC and GaN-on-Si HEMTs dominate the RF power amplifier market above 3 GHz for 5G base stations, radar, and electronic warfare. With power densities exceeding 8 W/mm at 30 GHz (compared to ~1 W/mm for GaAs), GaN enables higher output power from smaller die areas, reducing system cost and thermal management complexity in phased-array antenna elements.
UV Photodetectors
GaN and AlGaN-based metal-semiconductor-metal (MSM) and Schottky photodiodes provide solar-blind UV detection (200–365nm) with visible rejection ratios exceeding 10⁴. These detectors are essential for flame sensing, missile plume detection, and UV-C disinfection monitoring where immunity to ambient visible light is critical.
Space & Harsh Environment
GaN's wide bandgap (3.4 eV) provides inherent radiation hardness — displacement damage thresholds 10–100× higher than silicon. Combined with operating temperatures exceeding 500°C, GaN devices are qualified for satellite power systems, deep-space probes, and downhole geothermal instrumentation where silicon electronics cannot survive.
Metrology & Quality Assurance
Every GaN-on-Sapphire wafer lot is characterized through a comprehensive metrology protocol at ISO 9001:2015 certified facilities. The combination of XRD, PL mapping, AFM, and Hall effect measurements provides a complete picture of crystalline quality, optical uniformity, surface morphology, and electrical transport properties.
Need GaN-on-Sapphire Substrates?
Specify your diameter (2″–8″), GaN thickness, doping type (UID/N-type/P-type), and dislocation density grade — our wide-bandgap specialists will provide a detailed quotation with XRD, AFM, and PL mapping data within 24 hours.