An apparatus includes an enhancement mode transistor having multiple Group III-V layers above a substrate and a gate above the Group III-V layers. The gate includes multiple layers of material that form at least a portion of a thyristor. The multiple layers of material may include a first p-type layer of material, an n-type layer of material on the first p-type layer, and a second p-type layer of material on the n-type layer. The multiple layers of material may also include a p-type layer of material, an n-type layer of material on the p-type layer, and a Schottky metal layer on the n-type layer. The enhancement mode transistor may represent a high electron mobility transistor (HEMT) or a heterostructure field effect transistor (HFET).