A high electron mobility field effect transistor (HEMT) having a substrate, a channel layer on the substrate and a barrier layer on the channel layer includes a stress inducing layer on the barrier layer, the stress inducing layer varying a piezo-electric effect in the barrier layer in a drift region between a gate and a drain, wherein a two dimensional electron gas (2DEG) has a non-uniform lateral distribution in the drift region between the gate and the drain, wherein the stress inducing layer comprises a material having a height that decreases linearly and monotonically in the drift region in the direction from the gate towards the drain, and wherein the 2DEG decreases in density in the drift region between the gate and the drain.