Performance limiting inhomogeneities of defect states in ampere-class Ga2O3 power diodes

Abstract

Impacts of spatial charge inhomogeneities on carrier transport fluctuations and premature breakdown were investigated in Schottky ampere-class Ga2O3 power diodes. Three prominent electron traps were detected in Ga2O3 epilayers by a combination of the depth-resolved capacitance spectroscopy profiling and gradual dry etching. The near-surface trap occurring at 1.06 eV below the conduction band minimum (EC), named E3, was found to be confined within a 180 nm surface region of the Ga2O3 epilayers. Two bulk traps at EC − 0.75 eV (E2*) and at EC − 0.82 eV (E2) were identified and interconnected with the VGa- and FeGa-type defects, respectively. In the framework of the impact ionization model, employing the experimental trap parameters, the TCAD simulated breakdown characteristics matched the experimental breakdown properties well, consistently with inverse proportionality to the total trap densities. In particular, the shallowest distributed E3 trap with the deepest level is responsible for higher leakage and premature breakdown. In contrast, Ga2O3 Schottky diodes without E3 trap exhibit enhanced breakdown voltages, and the leakage mechanism evolves from variable range hopping at medium reverse voltages, to the space-charge-limited conduction at high reverse biases. This work bridges the fundamental gap between spatial charge inhomogeneities and diode breakdown features, paving the way for more reliable defect engineering in high-performance Ga2O3 power devices.