AlGaN/GaN heterojunction bipolar transistor

We demonstrate the first GaN bipolar transistor. An AlGaN/GaN HBT structure was grown by MOCVD on c-plane sapphire substrate. The emitter was grown with an Al/sub 0.1/Ga/sub 0.9/N barrier to increase the emitter injection efficiency. Cl/sub 2/ RIE was used to pattern the emitter mesa, and selectively regrown base contact pads were implemented to reduce a contact barrier associated with RIE etch damage to the base surface. The current gain of the devices was measured to be as high as three with a base width of 200 nm. DC transistor characteristics were measured to 30 V V/sub CE/ in the common emitter configuration, with an offset voltage of 5 V. A gummel plot and base contact characteristics are also presented.