Defects at the surface of beta-Ga2O3 produced by Ar plasma exposure

Abstract

Films of beta-Ga2O3 grown by halide vapor phase epitaxy on native substrates were subjected to Ar inductively coupled plasma treatment. As a result, the built-in voltage of Ni Schottky diodes deposited on the plasma treated surfaces decreased from 1 V to -0.02 V due to the buildup of deep trap concentration in the near surface region. Deep level spectra measurements indicate a strong increase in the top similar to 200 nm of the plasma treated layer of the concentration of E2* (Ec - 0.8 eV) and especially E3 (Ec - 1.05 eV) deep electron traps. Capacitance-voltage profiling with monochromatic illumination also indicated a large increase in the upper similar to 100 nm of the film in the concentration of deep acceptors with optical threshold for an ionization of similar to 2.3 eV and 3.1 eV. Such defects at the surface led to a significant increase in reverse current, an increase in the ideality factor in forward current, and a dramatic decrease in the diffusion length of nonequilibrium charge carriers from 450 nm to 150 nm.