Role of barrier structure in current collapse of AlGaN/GaN high electron mobility transistors

Simultaneous measurements of surface potential by Kelvin force microscopy and drain current detrapping transients in AlGaN/GaN high electron mobility transistors are performed on devices with two different epitaxial structures to understand if the trapped charges are predominantly in the AlGaN bulk, at the AlGaN surface, or in the GaN buffer. The results show that the predominant location of charge trapping is affected more strongly by the design of the device and the operating voltages than by surface passivation or buffer defects. The experiments also show that the dominant component of current collapse in devices with thick AlGaN barrier layers comes from AlGaN traps.