Trap-mediated bipolar charge transport in NiO/Ga2O3 p+-n heterojunction power diodes

The construction of p-NiO/n-Ga2O3 heterojunction becomes a popular alternative to overcome the technological bottleneck of p-type Ga2O3 for developing bipolar power devices for practical applications, whereas the identification of performance-limiting traps and the bipolar transport dynamics are still not exploited yet. To this end, the fundamental correlation of carrier transport, trapping and recombination kinetics in NiO/beta-Ga2O3 p(+)-n heterojunction power diodes has been investigated. The quantitative modeling of the temperature-dependent current-voltage characteristics indicates that the modified Shockley-Read-Hall recombination mediated by majority carrier trap states with an activation energy of 0.64 eV dominates the trap-assisted tunneling process in the forward subthreshold conduction regime, while the minority carrier diffusion with near-unity ideality factors is overwhelming at the bias over the turn-on voltage. The leakage mechanism at high reverse biases is governed by the Poole-Frenkel emissions through the beta-Ga2O3 bulk traps with a barrier height of 0.75 eV, which is supported by the identification of majority bulk traps with the energy level of E-C - 0.75 eV through the isothermal capacitance transient spectroscopic analysis. These findings bridge the knowledge gap between bipolar charge transport and deep-level trap behaviors in Ga2O3, which is crucial to understand the reliability of Ga2O3 bipolar power rectifiers.

Automated summary

This study investigates the fundamental correlation of carrier transport, trapping, and recombination kinetics in NiO/beta-Ga2O3 heterojunction power diodes. The findings reveal that majority carrier trap states dominate the trap-assisted tunneling process in the forward conduction regime, while minority carrier diffusion is important at higher biases. The leakage mechanism at high reverse biases is governed by Poole-Frenkel emissions through beta-Ga2O3 bulk traps.