EFFECTS OF NH3 ON THE GROWTH-RATE AND THE SURFACE-MORPHOLOGY OF GAAS IN CHLORIDE VPE

Effects of ammonia (NH3) on the growth rate and the surface morphology of GaAs were studied in chloride vapor phase epitaxy (C-VPE). We found that the NH3 addition increases the growth rate at the substrate temperatures of 640-680-degrees-C, but does not at higher temperatures in a conventional C-VPE method. For a single flat temperature zone (SFT) C-VPE method, an increase of the growth rate due to the NH3 addition was not observed in any growth temperature range. These results indicate that the NH3 addition enhances only the desorption of GaCl3, which is the rate determining step of conventional C-VPE at low temperatures. In addition to that, we found that the NH3 addition greatly suppressed the formation of hillocks which were often observed on the GaAs surface grown on (001)just-oriented substrates. A simple model of the mechanism will be proposed.