On the nature of deep-level defects in <i>β</i> -Ga2O3 epilayers: The impact of isochronal rapid thermal annealing

Abstract

Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate electrically active defects in (010)-oriented β-Ga2O3 epilayers grown via metal-organic chemical vapor deposition and doped with Si during growth. The impact of isochronal rapid thermal annealing in N2 on the electrical characteristics of Pt Schottky barrier diodes and on defect concentrations was examined by annealing at temperatures from 150 to 450 °C with 100 °C increments. Four deep levels were detected, with concentrations in the range of 1013–1014 cm−3 and activation energies of electron emission to the conduction band (ΔEc) of 0.06, 0.40, 0.55, and 0.62 eV. The Ec-0.06 eV trap was no longer observed in DLTS measurements after heating to 400 K, and the Ec-0.62 eV trap was suppressed after annealing at 350 °C. In contrast, the Ec-0.40 eV trap progressively reduced in concentration, while the trap density of the Ec-0.55 eV level increased with each rapid thermal annealing step, suggesting defect redistribution along the [010] direction. The electric field dependence of the electron emission rates indicates acceptor-like behavior for the Ec-0.55 eV state and donor-like behavior for the Ec-0.62 eV state. As both states exhibit activation energies consistent with the commonly reported E1 defect, we propose the following labelling conventions: E1a (Ec-0.55 eV) and E1b (Ec-0.62 eV). The nature and potential origins for each of the observed defects are discussed.