A high electron mobility transistor (HEMT) includes a substrate; a source on the substrate; a drain on the substrate spaced from the source; and a gate between the source and the drain, wherein the gate has a stem contacting the substrate, the stem having a source side surface and a drain side surface, wherein a source side angle is defined between the source side surface and an upper planar surface of the substrate and a drain side angle is defined between the drain side surface and the upper planar surface of the substrate, and wherein the source side angle and the drain side angle are asymmetric. Methods for making the HEMT are also disclosed.