Temperature Dependence of Photogenerated Carriers in GaN Layer of AlGaN/GaN HEMT

In this study, we irradiated light with energy greater than the bandgap of GaN from the top of the GaN-HEMT to generate photogenerated carriers in the GaN layer. By investigating the behavior of photogenerated carriers, we elucidated the carrier behavior in the GaN layer. Photogenerated carriers were generated under different temperatures. The temperature dependence of the high frequency characteristics of photogenerated carriers was also investigated. According to the results, the attenuation of high-frequency gain due to high temperature was canceled out by photogenerated carriers. Furthermore, analysis of the parasitic capacitance between the gate and source electrodes confirmed that the parasitic capacitance tended to increase as the drain voltage increased. The hole accumulation effect caused by photogenerated-carrier holes of near the source electrode was experimentally found to inhibit current gain amplification.