In order to optimize and improve the design of power devices with improved surge current safe operating area it is necessary to obtain a good correlation between measured and simulated space and time resolved temperature distributions. Therefore, an IR microscope capable of measuring the space and time resolved surface temperature distributions in Si power diodes operating under self-heating conditions has been developed. The minimum detectable spot size is 15 mum, while the signal rise time is detector limited to about 1 mus. The lower temperature detectivity limit is about 10 degreesC over room temperature. Using this instrument dynamic thermal phenomena in fast recovery 3.3 kV Si power diodes having radiation-induced recombination centers [Proceedings of the 7th EPE, Trondheim, 1997] subjected to 1.2 ms 400-2000 A/cm(2) and 0.3-2 ms 2000 A/cm(2) current pulses have been studied. The experimental results have been compared to results from 2D device simulations including surface recombination and carrier lifetime temperature dependence. The agreement between experimental and device simulation results (i.e. dynamic IV characteristics and time and space resolved temperature distributions) is very good up to a peak current density of 1500 A/cm(2), and a reasonable good one for peak current densities up to 2000 A/cm(2) (1.2 ins current pulses).