Trapping and Detrapping Mechanisms in beta-Ga2O3 Vertical FinFETs Investigated by Electro-Optical Measurements

We present a detailed investigation of the trapping and detrapping mechanisms that take place in the gate region of beta-Ga2O3 vertical finFETs and describe the related processes. This analysis is based on combined pulsed characterization, transient measurements, and tests carried out under monochromatic light, with photon energies between 1.5 and 5 eV. The original results presented in this article demonstrate that: (i) when submitted to positive gate stress with V-GS > V, the devices show a significant threshold voltage variation; (ii) this effect is not recoverable in 10 000 s in rest condition (zero bias, dark condition). (iii) V-TH can quickly recover its initial value when the device is illuminated with UV-C light at 280 nm. (iv) Stress-recovery experiments carried out at different photon energies allowed us to estimate the threshold energy for the release of carriers from the Al2O3/Ga2O3 interface, and for the injection of electrons from metal to the Al2O3 insulator (conduction band discontinuity at the metal/Al2O3 interface).