Characterization of heavily carbon-doped GaAs with a hole concentration of the order of 10 21 cm −3 grown by metalorganic molecular beam epitaxy and its application to InGaP/GaAs heterojunction bipolar transistors

Abstract

Ultra-high carbon-doping up to 10 21 cm −3 into GaAs is possible by metalorganic molecular beam epitaxy (MOMBE) technique using trimethylgallium (TMG) and elemental arsenic (As 4) as source materials. Room temperature photoluminescence (PL) of carbon-doped GaAs with such a high hole concentration showed the dominant emission by electron-acceptor transition. Local vibration mode (LVM) spectra were also measured by Raman scattering spectroscopy and Fourier transform infrared (FTIR) spectroscopy. It is revealed that carbon is fully incorporated on the arsenic lattice site despite the ultra-high doping regime, suggesting that there is no carrier compensation in the GaAs layers. Carbon-doped base In 0.5Ga 0.5P/GaAs heterojunction bipolar transistors (HBTs) with a hole concentration of 1.5 × 10 21 cm −3 in the base were fabricated by MOMBE for the first time. For the growth of In 0.5Ga 0.5P emitter, tertiarybutylphosphine (TBP), elemental In and elemental Ga were used as source materials. Small signal current gain h fe of 16 and DC current gain h FE of 12 were obtained for devices with a base thickness of 15 nm despite the ultra-high doping in the base layer. These results suggest that heavily carbon-doped GaAs with a hole concentration of 1.5 × 10 21 cm −3 is useful for the application to HBTs with heavily doped base layer.