Reliability aspects of GaN microwave devices

Rf drain-current (ID) collapse is the major factor limiting the output-power density at microwave frequencies in GaN-based FET's [1]. Its detrimental consequences on device performance have been put into evidence by using different experimental techniques, including measurements of pulsed ID vs drain-source-voltage (VDS) characteristics, gate- and drain-lag transients, transconductance (gm) frequency dispersion, rf response [1,2,3]. Several studies suggest that surface states can play a predominant role in originating the observed device behavior.