Nm-scale measurements of fast surface potential transients in an AlGaN/GaN high electron mobility transistor

Abstract

Fast, bias-induced, surface potential transients (SPTs) and conductance transients (CTs) were simultaneously measured on an AlGaN/GaN high electron mobility transistor. SPTs measured near the drain-side gate edge and CTs have nearly the same shape and are well-fit with two exponentials having room-temperature time constants of 4.2 ms and 36 ms, likely indicating emission from two trap species. Kelvin probe force microscopy was used to measure SPTs. Electrostatic simulations of SPT amplitudes, which account for the measured probe/sample geometry, are consistent with a uniform trapped surface charge density of 7 × 1012 electrons/cm2 extending 200 nm from the drain-side gate edge.