1. Core Product Advantages: Self-Developed Sapphire Substrates for Low-Cost Ga₂O₃ Epitaxy System
As a next-generation ultra-wide bandgap (UWBG) semiconductor, β-Ga₂O₃ features a 4.9 eV ultra-wide bandgap, an ultra-high breakdown field of 8 MV/cm, and excellent thermal stability, making it a core material for power devices and solar-blind ultraviolet photodetectors. At present, n-type doping technology for Ga₂O₃ is relatively mature in the industry. However, stable and controllable p-type doping remains a critical technical bottleneck, severely restricting the R&D and mass production of Ga₂O₃ PN junctions and bipolar power devices.
Our full series of c-plane (0001) polished
sapphire substrates serve as the optimal low-cost base for Ga₂O₃ heteroepitaxy. Compared with homoepitaxial Ga₂O₃ single-crystal substrates, they offer three major industrial advantages:
1.
Extreme Cost-Effectiveness: Sapphire fabrication technology is mature and stable, supporting mass delivery of 2/4/6/8-inch large-size substrates without precious metal consumption. It reduces the overall manufacturing cost of Ga₂O₃ epitaxial devices by more than 60%, perfectly suitable for large-scale production scenarios such as consumer fast chargers, home appliance inverters, and civilian ultraviolet detection devices.
2.
Full Process Compatibility: Featuring high flatness and stable lattice structure, the substrates are fully compatible with the complete semiconductor production process, including MOCVD epitaxial growth, ion implantation, high-temperature annealing and metal evaporation. No warpage, deformation or damage occurs under high-energy ion irradiation and 1000 °C high-temperature conditions, ensuring high and stable production yield.
3.
Excellent Optoelectronic and Thermal Performance: Sapphire exhibits high transmittance in the deep ultraviolet band, ideal for solar-blind UV device R&D. Its room-temperature thermal conductivity reaches 42 W/m·K, which efficiently dissipates heat generated by operating devices, compensates for the low thermal conductivity disadvantage of Ga₂O₃, and significantly improves the long-term reliability of power devices.
2. Complete Epitaxy and Phosphorus Doping Process Based on Sapphire Substrates
2.1 Epitaxial Thin Film Growth Process
Adopting our standard c-plane (0001) polished sapphire substrates, unintentionally doped (UID) β-Ga₂O₃ epitaxial layers with a precise thickness of 200 nm were grown via MOCVD at 875 °C. Triethylgallium (TEGa) was used as the Ga precursor and 99.999% high-purity oxygen as the O precursor, with a stable growth pressure of 15 Torr.
The as-grown undoped Ga₂O₃ epitaxial layer presents near-insulating characteristics with a resistance as high as 10¹⁴ Ω. Cooperated with our ultra-smooth sapphire substrates (surface roughness ≤ 0.3 nm), high-quality single-crystal epitaxial films with negligible defects and dislocations can be obtained.
2.2 Graded Phosphorus Ion Implantation Process (Sapphire Substrate Adapted)
Using the E220HP ion implantation system, ion implantation was performed at room temperature with a 7° incident angle. Three superimposed ion energies of 40 keV, 50 keV and 100 keV were adopted to solve the problem of uneven near-surface doping concentration caused by single-energy implantation, achieving uniform full-region doping. Three graded dosage levels were designed to meet diverse device performance requirements:
Low dosage: 2.5×10¹² ~ 1.6×10¹³ atoms/cm²
Medium dosage: 2.5×10¹³ ~ 1.6×10¹⁴ atoms/cm²
High dosage: 2.5×10¹⁴ ~ 1.6×10¹⁵ atoms/cm²
[Figure 1 ] SRIM simulation curves of phosphorus ion depth distribution (comparison of concentration and penetration depth under low, medium and high dosages)
2.3 High-Temperature Activation Annealing and Ohmic Contact Fabrication
After ion implantation, rapid thermal annealing (RTA) was performed at 1000 °C for 1 minute in a nitrogen atmosphere to activate dopants. The sapphire substrates maintained intact morphology without deformation or abnormal element precipitation, demonstrating excellent thermal stability. Subsequently, 20 nm/100 nm Ni/Au metal electrodes were deposited on the epitaxial surface, followed by secondary annealing at 600 °C for 1 minute in N₂ to form stable ohmic contacts for subsequent electrical testing and device fabrication.
3. Material Characterization and Electrical Performance Test Results
3.1 SIMS Depth Distribution Measurement
[Figure 2 ] SIMS depth distribution profiles of phosphorus elements (a: low dosage, b: medium dosage, c: high dosage; dotted line represents the sapphire/Ga₂O₃ interface)
The test results show that the phosphorus distribution of low-dosage samples is uniform with a peak concentration of 2×10¹⁸ cm⁻³, and no obvious interdiffusion occurs at the substrate-epitaxy interface. The peak phosphorus concentrations of medium and high-dosage samples reach 2×10¹⁹ cm⁻³ and 2×10²⁰ cm⁻³ respectively. Slight lattice damage induced by high-dose ion implantation causes minor Al-P interdiffusion, which can be completely optimized via our custom buffered
sapphire substrates. The experimental data is highly consistent with SRIM simulation results, proving that the substrate doping concentration is precise and repeatable.
3.2 Conductivity Type Identification via UPS Spectroscopy
[Figure 3 ] UPS valence band spectra of samples with different doping dosages (inset: schematic diagram of Fermi level position in the band gap)
The test results clearly distinguish conductivity types: low-dose doped samples show n-type insulating characteristics with the Fermi level close to the conduction band. Medium-dose samples exhibit standard p-type conductivity with a Fermi level valence band offset of 1.99 eV (located between the intrinsic level and valence band maximum). High-dose samples show further enhanced p-type characteristics with a reduced offset of 1.84 eV. The results verify that medium and high-dose phosphorus implantation on sapphire substrates effectively breaks the p-type doping bottleneck of Ga₂O₃.
3.3 Hall Electrical Performance Test
[Figure 4 ] I-V curves of Ni/Au ohmic contacts for medium and high-dose p-type Ga₂O₃ and schematic diagram of the test device structure
Low-dose samples exhibit excessively high resistivity with no valid electrical output. Stable p-type conductivity is successfully realized in medium and high-dose samples, with key electrical parameters as follows:
| Implantation Dosage |
Resistivity (Ω·cm) |
Hole Concentration (cm⁻³) |
Hole Mobility (cm²/V·s) |
| Medium Dosage |
9.699 |
1.612×10¹⁸ |
0.399 |
| High Dosage |
6.439 |
6.428×10¹⁷ |
1.51 |
4. Product Application Scenarios & Supporting Services
4.1 Core Application Scenarios
Consumer Power Devices: 650 V fast chargers and home appliance inverters, realizing large-scale mass production relying on sapphire’s cost advantages;
Solar-Blind UV Detection Devices: Utilizing sapphire’s high deep-UV transmittance for fire early warning, grid corona detection and environmental monitoring equipment;
Scientific R&D Iteration: 2/4-inch standard polished substrates for Ga₂O₃ doping process and device development in universities and research institutes.
4.2 Exclusive Supporting Services
Customizable multi-orientation sapphire substrates (c-
plane, r-plane, a-plane) with tailored Ga₂O₃ epitaxial buffer layer solutions;
Full technical support including substrate selection, MOCVD epitaxy and ion implantation parameter simulation;
Mass delivery of 4/6/8-inch large-size substrates to shorten customer production verification and mass production cycles.
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