Temperature distribution in Gunn diodes and GaAs MESFET's determined by micro-photoluminescence

It is shown that micro-photoluminescence (PL) may be used for evaluating the local temperature on the surface of GaAs microwave devices. This novel method is based on the phenomenon that the near-band-gap PL radiation of laser-beam irradiated GaAs shifts toward longer wavelengths, if its temperature increases. The intensity of the measured radiation is not important, an advantage as compared to other methods. The spatial resolution employed so far was about 20-50 µm. The reliability of the method is demonstrated for axial and planar Gunn diodes (dc and pulsed operation) and for two-gate GaAs MESFET's (where the mutual temperature influence of the channels is examined). The measuring accuracy achieved is 3 to 5°C. Satisfying agreement with theoretical calculations is obtained.