The trend of miniaturization and rapid progress in the cost-competitive microelectronic industry require high resolution, fast, accurate and cost-effective thermal characterization techniques. These techniques aid the assessment of reliability and performance benchmarking of new device designs for the realistic operation conditions. We present a time resolved, surface sensitive, sub-micron resolution wide field thermal imaging technique, exploiting fast radiative recombination rates of quantum rod photoluminescence to probe temperature transients in semiconductor devices. We demonstrate a time resolution of 20 s on a single finger AlGaN/GaN HEMT. This technique provides an image of the surface temperature transients regardless of the device design/material system under test. The results were verified with transient thermo-reflectance measurements.