The present disclosure, in some embodiments relates to a semiconductor device. The semiconductor device includes a layer of semiconductor material disposed over a substrate and an electron supply layer disposed over the layer of semiconductor material between an anode terminal and a cathode terminal. A layer of III-N (III-nitride) semiconductor material is disposed over the electron supply layer. A passivation layer contacts an upper surface of the electron supply layer and further contacts an upper surface and a sidewall of the layer of III-N semiconductor material. A gate structure is separated from the layer of III-N semiconductor material by the passivation layer.