A semiconductor device includes a channel layer, a barrier layer, source contact and a drain contact, a doped group III-V layer, and a gate electrode. The barrier layer is positioned above the channel layer. The source contact and the drain contact are positioned above the barrier layer. The doped group III-V layer is positioned above the barrier layer and between the first drain contact and the first source contact. The first doped group III-V layer has a first non-vertical sidewall and a second non-vertical sidewall. The gate electrode is positioned above the doped group III-V layer and has a third non-vertical sidewall and a fourth non-vertical sidewall. A horizontal distance from the first non-vertical sidewall to the third non-vertical sidewall is different than a horizontal distance from the second non-vertical sidewall to the fourth non-vertical sidewall.