Trapping in $\text{Al}_{2}\mathrm{O}_{3}/\text{GaN}$ MOScaps investigated by fast capacitive techniques

We present a detailed investigation of charge trapping processes in $\text{Al}_{2}\mathrm{O}_{3}/\text{GaN}$ vertical MOS capacitors, detected by means of advanced capacitance measurements. The devices stressed at positive bias present a trapping mechanism that results in an increase of the flatband voltage, while under negative voltages the negative charge stored in bulk and interface states is released with a leftward shift of the C-V characteristic. We also demonstrated that the formation of the hump in depletion regime is the result of trapping of electrons at the oxide-semiconductor interface. The detected behavior is modeled by considering the $\mathbf{D_{IT}}$ profile extrapolated by photoassisted CV measurements. The results provide relevant input for the design of stable and reliable MOS transistors based on GaN.