Drain barrier lowering in HEMTs

Drain barrier lowering gives pinchoff voltages that vary as /spl gamma/Vds, which affects the output conductances. The factor /spl gamma/ depends on the channel aspect ratio X=/spl pi/L/4d, where L is the effective gate length and d is the effective channel depth. For low output conductances we need to minimize /spl gamma/ and maximize the channel aspect ratio X. This paper uses 2D simulations to delineate the effective L and d parameters, and illustrates what can be done to the layer design to minimize d.