High current gain In0.49Ga0.51P/GaAs heterojunction bipolar transistors with double spacers grown by gas source molecular beam epitaxy

This paper reports the improved performance of the lattice-matched N-p(+)-n In0.49Ga0.51P/GaAs heterojunction bipolar transistors(HBTs) with undoped spacers grown by the gas source molecular beam epitaxy. A 600 Angstrom GaAs base doped with beryllium at 3 x 10(19) cm(-3) and a 1000 Angstrom In0.49Ga0.51P emitter doped with silicon at 3 x 10(17) cm(-3) have been grown. On both sides of the base, the 50 Angstrom undoped GaAs spacers were grown. Devices with emitter area of 100 x 100 mum(2) were fabricated by using selective wet chemical etching technique. The measured results of HBTs reveal good junction characteristics, and the common-emitter current gain reaches 320 at the collector current density of 280 A/cm(2).