Trap characterization in ultra-wide bandgap Al0.65Ga0.4N/Al0.4Ga0.6N MOSHFET's with ZrO2 gate dielectric using optical response and cathodoluminescence

Abstract

Ultrawide bandgap (UWBG) AlGaN-channel metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with a ZrO2 gate dielectric achieve peak current in excess of 0.4 A/mm and current ON/OFF ratios >106 with subthreshold swings as low as 110 mV/decade. These devices have strong potential for use in power and radio frequency electronics or as true solar-blind photodetectors. In this work, we present the photoresponse analysis in UWBG AlGaN MOSHFETs. Persistent photoconductivity with the decay time above 10 minutes can be quenched by illuminating with strong UV light at 365 nm and 254 nm, suggesting deep traps to be responsible for this behavior. Upon correlating the optical response under various illumination conditions with cathodoluminescence of these devices, we identified two key trap levels at ∼2.48 ± 0.14 eV and 3.76 ± 0.06 eV, controlling the slow response time. By depth-profiling using cathodoluminescence, these traps are identified to be at the AlN/AlGaN interface at the back of the device, due to partial relaxation from the lattice mismatch between AlN and Al0.4Ga0.6N.