A method of making a high-electron mobility transistor (HEMT) includes forming an unintentionally doped gallium nitride (UID GaN) layer over a silicon substrate, a donor-supply layer over the UID GaN layer, a gate, a passivation layer over the gate and portions of the donor-supply layer, an ohmic source structure and an ohmic drain structure over the donor-supply layer and portions of the passivation layer. The source structure includes a source contact portion and an overhead portion. The overhead portion overlaps the passivation layer between the source contact portion and the gate, and may overlap a portion of the gate and a portion of the passivation layer between the gate and the drain structure.