High-temperature low-pressure chemical vapor deposition of β-Ga2O3

Abstract

Recent advancements in β-Ga2O3 materials’ growth and device developments are briefly reviewed with the focus on low-pressure chemical vapor deposition (LPCVD) of β-Ga2O3. β-Ga2O3 films are grown on off-axis c-sapphire and (010) β-Ga2O3 substrates via high-temperature LPCVD (HT-LPCVD) with growth temperatures ranging between 950 and 1050 °C. The effects of HT-LPCVD growth conditions on material properties are comprehensively studied. With relatively higher growth temperatures, an increased O2 flow rate is required to maintain β-Ga2O3 crystalline quality with high electron mobility. The growth rate of the HT-LPCVD β-Ga2O3 film scales with the increase of growth temperature and O2 flow rate. The film growth rate is strongly related to the sapphire substrate off-axis angle, which determines the preferred nucleation sites from the step edges. The transport properties of samples grown on substrates with different off-axis angles are compared. The optimized growth temperature for obtaining films with high electron mobility varies with the off-axis angle. From this comprehensive study, high-quality β-Ga2O3 films grown on c-sapphire are achieved with room temperature mobilities of 126 cm2/V s (6° off-axis c-sapphire), 116 cm2/V s (8° off-axis c-sapphire), and 119 cm2/V s (10° off-axis c-sapphire) at carrier concentrations of mid-1016 cm−3. β-Ga2O3 LPCVD homoepitaxy optimized at elevated growth temperatures is performed on Fe-doped semi-insulating (010) Ga2O3 substrates. With controllable Si doping, record-high room temperature mobilities of 156 cm2/V s (150 cm2/V s) are achieved with doping concentrations of 3 × 1016 cm−3 (1.5 × 1017 cm−3) at a growth temperature of 1050 °C. Secondary ion mass spectroscopy analysis shows more than an order of magnitude reduction of C and H impurity incorporation with increased growth temperature. Results from this work demonstrate that HT-LPCVD growth is a promising method to produce high-quality β-Ga2O3 films on both off-axis c-sapphire and native Ga2O3 substrates with a fast growth rate and superior transport properties critical for high power device applications.