Thermal and trapping effects in GaN-based MESFETs

RF power performances of GaN-MESFETs are reported using a physics-based model that incorporates dispersion in the output resistance and transconductance due to traps and thermal effects. Calculated I-V characteristics are in excellent agreement with the measured results. Taking thermal effects into account, the maximum output power of a 0.3 μm×100 μm GaN MESFET is 22 dBm at a power gain of 4.2 dB at 4 GHz. The corresponding quantities are 27 dBm and 6.4 dB, respectively if a constant channel temperature of 300 K is assumed. At elevated temperatures, compression in output power, gain and PAE is less in MESFETs with longer gate lengths.