Deep-Level Defect Investigation of Si-Doped $\beta$-Ga2O3 Homoepitaxial Films Grown by Halide Vapor Phase Epitaxy

Abstract

We have electrically investigated deep-level defects in Si-doped $\beta$ -Ga 2 O 3 homoepitaxial films grown by halide vapor phase epitaxy (HVPE), employing capacitance-voltage (C-V) and steady-state photo-capacitance spectroscopy (SSPC) techniques. The optical bandgap was determined to be ~4.6 eV from Tauc plots. From differential 1/C2-V plots, the effective n-type carriers $(\vert \mathrm{N}_{\mathrm{d}}-\mathrm{N}_{\mathrm{a}}\vert)$ with $\sim 4.2\mathrm{x}10^{16}\mathrm{cm}^{-3}$ were seen to be almost uniformly distributed. SSPC measurements revealed four positive deep-level defects (T1, T2, T3, T4, and T6) with their optical onsets at ~1.77, ~2.45, ~2.78, ~3.18, and ~3.88 eV below the conduction band and two negative deep-level defects (T5 and T7) with their optical onsets at ~3.67 and ~4.0 eV above the valence band. In particular, the ~3.67 eV and ~4.0 eV levels were found to be significantly enhanced compared to those in undoped $\beta$ -Ga 2 O 3 substrates and are probably attributable to oxygen vacancies produced by Si doping into $\beta$ -Ga 2 O 3 epitaxial films during the HVPE growth. In addition, the ~3.88 eV level with precipitous photo-capacitance change is likely associated with dislocations and/or surface defects $\beta$ -Ga 2 O 3 homoepitaxial films.