GaN Bipolar Junction Transistors with Regrown Emitters

Small-area ( 3 × 10 μ m emitter) GaN bipolar junction transistors (BJTs) incorporating a superlattice GaN(Mg)/AlGaN(Mg) base contact layer and a selectively regrown emitter were fabricated using a self-aligned dry etch process. The dc current gains were typically 10 at 25°C, and the devices were operated up to emitter current densities of 15 kA cm −2 . The BJTs exhibited high emitter injection efficiency, indicating the presence of a good interface between the initial epi structure and the regrown emitter.