Role of hole trapping by deep acceptors in electron-beam-induced current measurements in β-Ga2O3 vertical rectifiers

Abstract

Current increases in vertical-geometry Ga2O3 rectifiers during electron-beam-induced current measurements are dominated by the impact ionization of deep acceptors in the depletion region. At room temperature, mobile hole diffusion in the quasi-neutral region of Schottky diodes contributes significantly to the charge collection efficiency. Even when electron–hole pairs are created well inside the space charge region, there are significant losses of charge collection efficiency due to the trapping of holes by deep acceptors in the lower half of the bandgap. Capacitance–voltage profiling under illumination points to deep acceptors with optical ionization close to 2.3 eV as the most important agents of capture. Collection efficiency can be improved by increasing the electric field in the space charge region. The jump in collection efficiency at electric fields close to (5–6) × 105 V cm−1 is attributed to the impact ionization of these deep acceptors. These processes can manifest themselves in measurements of the impact ionization coefficients and breakdown voltages of β-Ga2O3 rectifiers and in analyses of the response times of β-Ga2O3 photodetectors.