VERY HIGH-CARBON INCORPORATION IN METALORGANIC VAPOR-PHASE EPITAXY OF HEAVILY DOPED P-TYPE GAAS

Very high C incorporation (> 10(20) cm-3) in GaAs was achieved by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) using CCl4 as a dopant gas. Hole densities up to p = 1.2 x 10(20) cm-3 (at least three times higher than previously reported by MOVPE) were obtained at a growth temperature of 600-degrees-C and a V/III ratio of 2.8. The highest atomic C concentration was 1.5 x 10(20) cm-3. The hole mobilities were approximately 50% larger than previously reported. CCl4 was found to suppress the formation of gallium droplets and whisker growth which normally occur under low-temperature, low V/III ratio growth conditions, allowing the growth of thin (< 1-mu-m) heavily doped layers with mirror-like surface morphologies. Layers with p approximately 1 X 10(20) cm-3 showed a lattice contraction with DELTA-a/a = -9.3 X 10(-4). Photoluminescence studies indicate a significant band-gap shrinkage at high doping levels.