Deep traps in Ga2O3 Schottky diodes induced by soft electric breakdown

Abstract

We report the electrical characteristics and deep trap behavior of vertical Ga₂O₃ Schottky diodes with diameters ranging from 200 to 380 μm, fabricated on commercial n/n⁺ epistructures. There was a significant inverse relationship between diode diameter and breakdown voltage (V_B). Specifically, the V_B for a 200 μm diameter diode was 330 V, decreasing to 225 V for 300 μm, and further to 200 V for 380 μm diameter diodes. This scaling is attributed to pre-existing extended defects and those forming under high voltage stress, which act as localized electric field concentrators and enhance current leakage. Electron beam induced current (EBIC) mapping post-breakdown revealed new bright spots and lines within the diodes, indicative of increased local current gain due to defect agglomerates. Following breakdown, a pronounced increase in reverse current was observed at low voltages, which is explained by Poole–Frenkel hopping. This hopping mechanism is predominantly mediated by deep centers with energy levels near E_c −0.7 eV, identified as the dominant E2* traps from pre-breakdown deep trap spectra. While capacitance deep level transient spectroscopy (DLTS) showed only slight changes in trap concentrations, current deep level transient spectroscopy (CDLTS) exhibited a strong signal for E1 and E2* traps after breakdown, suggesting a non-uniform formation of these centers in the vicinity of extended defects, leading to enhanced localized leakage.