Trapping effects and microwave power performance in AlGaN/GaN HEMTs

The dc, small-signal, and microwave power output characteristics of AlGaN/G aN HEMTs are presented. A maximum drain current greater than 1 A/mm and a g ate-drain breakdown voltage over 80V have been attained. For a 0.4 mum gate length, an f(T) of 30 GHz and an f(max) of 70 GHz have been demonstrated. Trapping effects, attributed to surface and buffer layers, and their relati onship to microwave power performance are discussed, It is demonstrated tha t gate lag is related to surface trapping and drain current collapse is ass ociated with the properties of the GaN buffer layer. Through a reduction of these trapping effects, a CW power density of 3.3 W/mm and a pulsed power density of 6.7 W/mm have been achieved at 3.8 GHz.