Certain aspects of the present disclosure provide a high electron mobility transistor (HEMT). The HEMT generally includes a gallium nitride (GaN) layer and an aluminum gallium nitride (AlGaN) layer disposed above the GaN layer. The HEMT also includes a source electrode, a gate electrode, and a drain electrode disposed above the AlGaN layer. The HEMT further includes n-doped protuberance(s) disposed above the AlGaN layer and disposed between at least one of: the gate electrode and the drain electrode; or the source electrode and the gate electrode. Each of the n-doped protuberances is separated from the gate electrode, the drain electrode, and the source electrode.