High Current Gain In_0.49Ga_0.51P/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 In_0.49Ga_0.51P/GaAs heterojunction bipolar transistors(HBTs) with undoped spacers grown by the gas source molecular beam epitaxy. A 600 Å GaAs base doped with beryllium at 3 x 10¹⁹cm^-3 and a 1000 Å In_0.49Ga_0.51P emitter doped with silicon at 3 x 10¹⁷cm^-3 have been grown. On both sides of the base, the 50 Å undoped GaAs spacers were grown. Devices with emitter area of 100 x 100 μm² were fabricated by using selective wet chemical etching technique. The measured results of HBTs reveal cood junction characteristics, and the common-emitter current gain reaches 320 at the collector current density of 280 A/cm².