Ge Doping in LPCVD-Grown (010) β-Ga2O3 Homoepitaxial Films: Structural, Electrical, and Schottky Diode Characteristics

Abstract Ge-doped β-Ga2O3 homoepitaxial films were grown on native (010) β-Ga2O3 substrates using low-pressure chemical vapor deposition (LPCVD). Controlled n-type doping was achieved with room-temperature carrier concentrations ranging from 7.4×1017 to 2.57×1018 cm−3 and corresponding electron mobilities of 105−62 cm2/V·s. The films exhibited smooth surface morphology with RMS roughness values of 2.94−3.97 nm, while X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed phase-pure β-Ga2O3 with excellent crystalline quality and near-stoichiometric composition. Temperature-dependent Hall measurements on the film with a room-temperature carrier concentration of 7.4×1017 cm−3 and mobility of 105 cm2/V·s yielded a peak electron mobility of 234 cm2/V·s at 116 K, while charge-neutrality and transport modeling revealed a dominant shallow donor level with an activation energy of 14 meV, confirming efficient electrical activation of Ge donors. Vertical Ni/β-Ga2O3 Schottky barrier diodes fabricated using the Ge-doped drift layer exhibited good rectifying behavior with a turn-on voltage of 0.74 V, an ideality factor of 1.32, a Schottky barrier height of 1.02 eV, and a specific on-resistance of 2.49 mΩ·cm2. Capacitance−voltage measurements yielded a net donor concentration of 7.7×1017 cm−3 and a Schottky barrier height of 1.06 eV, in good agreement with Hall and current−voltage measurements. These results demonstrate that LPCVD enables controllable Ge doping while maintaining high structural and electronic quality, establishing LPCVD-grown Ge-doped β-Ga2O3 as a promising platform for future high-voltage power electronic devices.