High carbon doping of Ga1-xInxAs /x about 0.01/ grown by molecular beam epitaxy

We have grown layers of Ga1-x Inx As: C (x ~ 0.01) on (100) GaAs by molecular beam epitaxy. As C source a graphite filament was used. Structures coherent with the substrate were obtained by adjusting properly the In and C concentrations. With simultaneous incorporation of In and C the strain is compensated and, consequently, the defect density is reduced. A maximum hole concentration value of p = 6 x 10 19 ccm was achieved, which is twice higher than the saturation value of C doping of GaAs produced under the same conditions. There is evidence that this value is not in the saturation limit. The product of the hole density times the mobility increases, so the resistance decreases with higher C doping. Raman spectra show that the CAS peak broadens and shifts to lower frecuencies for increasing concentration of indium. In H-passivated samples, Raman spectroscopy shows that CAS is surrounded by Ga atoms only. Indium, atoms are thus present only in the second group III shell.