GaN/SiC heterojunction bipolar transistors

Heterojunction bipolar transistors made from GaN emitter and SIC base and c ollector regions are desired for high power, broad bandwidth microwave ampl ifiers. Their most critical element is the quality of the base-emitter junc tion. High efficiency emitter injection requires an interface between these lattice-mismatched materials, which does not produce significant leakage c urrent due to defects, in addition to having desirable band-offsets. An imp ortant factor in understanding GaN/SiC heterojunction rectification is acco unting for spontaneous polarization and piezoelectric effects. Theory is pr esented which shows that a strained GaN/SiC junction will form a 2D hole ga s in the base, while an unstrained junction will form a 2D-electron gas. Ex tending the critical thickness of GaN grown on SiC using patterned area gro wth might permit improved interface properties. (C) 2000 Elsevier Science L td. All rights reserved.