Determination of channel temperature for AlGaN/GaN HEMTs by high spectral resolution micro-Raman spectroscopy

Channel temperature determinations of AlGaN/GaN high electron mobility transistors (HEMTs) by high spectral resolution micro-Raman spectroscopy are proposed. The temperature dependence of the E2 phonon frequency of GaN material is calibrated by using a JYT-64000 micro-Raman system. By using the Lorentz fitting method, the measurement uncertainty for the Raman phonon frequency of +/- 0.035 cm(-1) is achieved, corresponding to a temperature accuracy of +/- 3.2 degrees C for GaN material, which is the highest temperature resolution in the published works. The thermal resistance of the tested AlGaN/GaN HEMT sample is 22.8 degrees C/W, which is in reasonably good agreement with a three dimensional heat conduction simulation. The difference among the channel temperatures obtained by micro-Raman spectroscopy, the pulsed electrical method and the infrared image method are also investigated quantificationally.