We report on the development of Time-resolved Ultraviolet Micro-Raman Scattering to measure transient self-heating effects in semiconductor devices. Temperature measurements are performed on AlGaN/GaN High-electron-mobility transistors (HEMTs) grown on SiC substrate. Ultraviolet excitation probes the temperature close to the AlGaN/GaN interface, in the two-dimensional electron gas (2DEG) region. This new measurement setup allows us to obtain a temporal, spectral and measured spatial resolution of 200 ns, 0.8 cm(-1) and 1.7 mu m respectively. The temperature accuracy is better than 5-10 K. Temperature evolution as function of time has been studied. Self-heating effects are immediately observed. A fast thermal response is demonstrated during the first microsecond after switching the device ON then, a slower thermal response is established during the second microsecond. (C) 2010 Elsevier Ltd. All rights reserved.