Generation and metastability of deep level states in β-Ga2O3 exposed to reverse bias at elevated temperatures

Abstract

An intriguing phenomenon of electrically active defect generation is observed in homoepitaxial β-Ga2O3 films exposed to reverse bias at elevated temperatures. In particular, heating samples up to 675 K in the course of deep level transient spectroscopy measurements, i.e., with the reverse bias and voltage pulsing applied, resulted in the generation of three new levels at ∼1, ∼1.5, and ∼2 eV below the conduction band edge (labeled as E3*, E5, and E6). The corresponding defects exhibit different thermal stabilities; E5 and E6 show stability, while E3* demonstrates a remarkable metastability—it can be generated, annealed out, and regenerated in the course of sequential temperature cycles. Combining a number of annealing tests and using different types of epitaxial materials, the levels were systematically investigated, and the most credible scenario behind the phenomenon is the evolution of already existing defect configurations provoked by the applied temperature and bias.