Multi-gate pHEMT modeling for high-power operation

Multi-gate pHEMTs are key elements in switch circuits in wireless communication applications due to their low loss and high power capacity with relatively small sizes. A great concern on their high power operation is the power step-back at on-state and at certain power level with harmonics deteriorated. In this paper we discuss the mechanism of power step-back. The power that can pass through an on-state pHEMT is dependent on saturation current, or the maximum available channel current. A premature power step-back or gain collapse in a multi-gate pHEMT is due to largely reduced saturation channel current caused by self-heating in center gate or gates. We developed a self-heating thermal model for multi-gate pHEMTs that can predict power level at that the power step-back and related hysteresis occur.