Time-resolved nanosecond sub-micron resolution thermal analysis of high-power AlGaN/GaN HFETs

Abstract

A novel time-resolved micro-Raman thermography technique has been developed to measure the active region temperature in AlGaN/GaN electronic devices, achieving a temporal and spatial resolution of 200 ns and 0.5-0.7 μm, respectively. AlGaN/GaN heterostructure field effect transistors (HFETs) grown on SiC and sapphire substrates are compared. Rapid temperature changes within 200 ns of current changes are followed by a slower change in device temperature. For a device on a SiC substrate an approximate temperature plateau is reached within 1-2 μs after switching the device on or off, illustrating its fast thermal response. This is in contrast to the slower time constant of devices on sapphire substrates where (is-separated electrical pulses do not allow the devices to cool to room temperature between the electrical pulses.