A study was made of the stability of C-related and native point defects, and the p-type doping levels of these 2 materials were compared by performing first-principles pseudopotential calculations. In the case of GaAs, a substitutional C acceptor at an As site was found to be a predominant defect, and the hole density saturated at about 1020/cm3. This was attributed mainly to compensation by [100] split-interstitial C-C complexes in the high-doping regime. In the case of InAs, the CAs acceptor was most stable among C-related defects. However, its formation energy was higher than for an As antisite or an In vacancy in the As-rich limit. The incorporation of C into bulk InAs was more difficult, as compared with GaAs, since C-related defects in InAs required higher formation energies. This resulted in lower hole densities in InGaAs alloys. When C occupied an In site in InAs, the associated defect level was found to lie below the valence band maximum. But this energy level moved to above the valence band maximum with increasing pressure.

K.J.Chang, S.G.Lee, B.H.Cheong: Materials Science Forum, 1995, 196-201, 803-8