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Heavily carbon-doped p-GaAs layers with a hole concentration of 1.5 × 10 21 −3.4 × 10 18 cm -3 were grown by metalorganic molecular beam epitaxy (MOMBE). The carrier concentration agrees well with the carbon concentration measured by SIMS, which suggests 100% of electrical activation of the incorporated carbon as an acceptor. The p-n diodes with carbon-doped p-GaAs show good rectification. The lattice constant of GaAs decreases with increasing carbon concentration. The carbon-doped InGaAs with a hole concentration of 2.6 × 10 20 cm -3 , lattice-matched with a GaAs substrate, was obtained for the first time. The effective bandgap narrowing in heavily doped GaAs was also studied by photoluminescence. The measured bandgap with a hole concentration of 10 20 cm -3 is about 100 meV lower than that of intrinsic GaAs. Finally, the static and high-frequency characteristics of heterojunction bipolar transistors with carbon-doped p-GaAs were calculated.

In order to overcome a problem of the lattice mismatch between heavily carbon-doped p-GaAs and moderately doped GaAs, we have grown heavily carbon-doped InGaAs with a hole concentration of 2.6×1020 cm-3 and resistivity of 6.5×10-4 Ω·cm by MOMBE, in which the indium content was adjusted so that its lattice constant became equal to that of SI GaAs. In the lattice-matched InGaAs, the indium molar fraction determined from the Raman spectrum and the bandgap from the 4.2 K photoluminescence spectrum are 0.05 and 1.396 eV, respectively.

The potential of metalorganic molecular beam epitaxy (MOMBE) for the growth of extremely low resistivity p-tape GaAs and GaAlAs has been investigated. The acceptor is carbon which is incorporated from trimethylgallium. The hole concentration was controlled in the range 10 19 -10 21 cm -3 by changing the growth temperature. The highest hole concentrations of 1.5×10 21 and 2.5×10 21 cm -3 have been obtained for GaAs and GaAlAs with the Al mole fraction of 0.35, respectively, which are higher than any other values reported for p-type epitaxial GaAs and GaAlAs thin films. The growth mechanism and detailed electrical properties have been discussed. It was found that the behavior of carbon as an acceptor is much more suitable than that of beryllium for device applications, which require thin layers with ultra low resistivity.

Band gap narrowing in heavily doped p-type GaAs is estimated by photoluminescence measurement. Measured values agree well with the theoretical results. Monte Carlo simulation of minority electron transport demonstrates that plasmon scattering plays an essential role in heavily doped p-type GaAs. Theoretical calculations, including these heavy doping effects, on heterojunction bipolar transistors (HBT's) show that maximum oscillatiorn frequency of over 300 GHz is expected by increasing the hole concentration of the base layer to 1×1021 cm-3.

We have investigated the potential of metalorganic molecular beam epitaxy (MOMBE) for the growth of extremely low resistivity p-type GaAs and GaAlAs. Heavily doped GaAs and GaAlAs epilayers with a carrier concentration of 5 × 1020-1 × 1021cm-3 were successfully grown by MOMBE. The acceptor was carbon which was incorporated from TMG. The thermal diffusion coefficient was much lower than that of Be, and the lattice constant did not vary with increasing carrier concentration. The behavior of carbon as an acceptor is very suitable for device applications, which require thin layers with ultra-low resistivity.

p‐type GaAs with doping levels of up to 5.8×1020 cm−3 has been grown by metalorganic molecular‐beam epitaxy (MOMBE) using carbon (C) as a dopant. The mobility and minority‐carrier diffusion length of the C‐doped MOMBE layers were comparable to those of Be‐doped MBE layers. The diffusion coefficient of C at 900 °C was estimated to be 6×10−15 cm2 /s which is about two orders of magnitude less than that of Be (1×10−12 cm2 /s). In addition, the lattice constant of C‐doped GaAs was found to be 5.6533 A which completely matches that of the substrate, while the lattice constant of Be‐doped GaAs decreases to 5.6467 A at a doping level of 2×1020 cm−3 as reported by Lievin et al. [Inst. Phys. Conf. Ser. No. 79, 595 (1985)].