CARBON DOPING AND ETCHING OF MOCVD-GROWN GAAS, INP, AND RELATED TERNARIES USING CCL4

Pure carbon tetrachloride is shown to be an excellent carbon-doping source for MOCVD-grown GaAs, but an etchant, rather than a doping source, for InP. Similar to the equilibria used in chloride vapor phase epitaxy, the etching (or reduced growth rate) is believed to occur because of the formation of InCl. In the case of Ga0.5IN0.5P, this etching is manifested by a change in the alloy composition, since the InP etches faster than the GaP. The composition of Ga0.5In0.5As is not changed significantly for comparable carbon tetrachloride flows. The doping efficiency of CCl4 for GaAs is shown to decrease sharply with the growth temperature and to be inversely proportional to the V/III ratio. The hole mobilities for carbon-doped GaAs are shown to be as high or higher than for zinc-doped GaAs. Compensation is not a problem, even at hole concentrations exceeding 10(19) cm-3. However, the quality of carbon-doped Ga0.5In0.5P films is significantly lower than that of zinc-doped Ga0.5In0.5P, and hole concentrations could not be increased above 10(17) cm-3. The carrier concentration of InP films is unaffected by the flow of carbon tetrachloride.