Suppression of current dispersion in AlGaN/GaN MISHFETs with in-situ AlN passivation layer

Abstract

We demonstrate effective reduction of interface states and current collapse in AlGaN/GaN metal insulator semiconductor heterostructure field effect transistor (MISHFETs) with Al2O3 and in-situ AlN passivation layer. Here, first, a 3 nm-thick in-situ AlN layer is grown on AlGaN/GaN structure by using MOCVD at 1070 °C, and second a 7 nm-thick atomic layer deposition (ALD) Al2O3 layer is immediately deposited on the AlN layer. The X-ray photoelectron spectroscopy (XPS) analyses for the Ga 3d core level and multi-frequency capacitance–voltage (C–V) measurement show that the density of interface states originated from the Ga-O bonds, which is dramatically reduced with the in-situ AlN passivation layer. The AlGaN/GaN-based MISHFET with the Al2O3/in-situ AlN layers exhibits the low gate-lag effect (8%), remarkably less than that of the device with the typical GaN capping layer (21.5%). These results indicate that the Al2O3/in-situ AlN double passivation layer is very effective in suppressing the current collapse, and hence, it is found to be the promising method for the fabrication of AlGaN/GaN MISHFETs with enhanced performance.