An AlGaN/GaN heterojunction bipolar transistor was grown onto a substrate by using the lateral epitaxial overgrowth technique. Active layers were grown, by means of plasma-assisted molecular-beam epitaxy, onto metal-organic chemical vapour deposition-grown templates on sapphire. The collector-emitter leakage mechanism in the devices was found to be a local punch-through which was associated with base-layer compensation near to the dislocations. The (non-dislocated) lateral epitaxial overgrowth wing-regions were found to reduce emitter-collector leakage by 4 orders of magnitude over adjacent window regions which had a dislocation density of 108/cm2. Varying the dopant profile through the base confirmed that the leakage mechanism was local punch-through due to compensation.

Effect of Threading Dislocations on AlGaN/GaN Heterojunction Bipolar Transistors. L.McCarthy, I.Smorchkova, H.Xing, P.Fini, S.Keller, J.Speck, S.P.DenBaars, M.J.W.Rodwell, U.K.Mishra: Applied Physics Letters, 2001, 78[15], 2235-7