Continuous time-domain RF waveforms monitoring under overdrive stress condition of AlGaN/GaN HEMTs

Abstract

This paper reports an advanced time-domain methodology to investigate the device reliability and determine its safe operating area of AlGaN/GaN HEMTs. The presented technique is based on the continued monitoring of the RF waveforms and DC parameters in order to assess the degradation of transistor characteristics in RF power amplifiers. The reliability study is carried out in class AB operation, under RF operating excitation at high drain voltages and overdrive conditions (12dB compression). The analysis is carried out with two different output load impedances: optimum of PAE and mismatched impedance. The results show a drift of RF performances due to a variation of electrical parameters. In particular, the operation with optimum PAE load impedance induces slight positive threshold voltage shift. The operation with mismatched load shows a stronger degradation, with a positive threshold voltage shift and a drop in saturation drain current, due principally to the high temperature reached by the devices during RF stress.