Characterization of heavily carbon-doped GaAs with a hole concentration of the order of 1021 cm−3 grown by metalorganic molecular beam epitaxy and its application to InGaP/GaAs heterojunction bipolar transistors

Abstract

Ultra-high carbon-doping up to 1021 cm−3 into GaAs is possible by metalorganic molecular beam epitaxy (MOMBE) technique using trimethylgallium (TMG) and elemental arsenic (As4) 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 In0.5Ga0.5P/GaAs heterojunction bipolar transistors (HBTs) with a hole concentration of 1.5 × 1021 cm−3 in the base were fabricated by MOMBE for the first time. For the growth of In0.5Ga0.5P emitter, tertiarybutylphosphine (TBP), elemental In and elemental Ga were used as source materials. Small signal current gain hfe of 16 and DC current gain hFE 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 × 1021 cm−3 is useful for the application to HBTs with heavily doped base layer.