MOLECULAR-BEAM EPITAXY ON EXACT AND VICINAL GAAS(1)OVER-BAR-(1)OVER-BAR-(1)OVER-BAR

GaAs films grown on exact (111BAR) substrates in the square-root 19 X square-root 19 reconstruction regime always show facets. The facets are composed of vicinal surfaces which are inclined by small angles (approximately 2-degrees) from the exact (111BAR) plane. The comparison between surface morphologies of films grown on vicinal substrates tilted toward different directions shows that the most stable steps run along the [110] directions and step downward toward the [112BAR], [211BAR], and [121BAR] directions. In the square-root-19 X square-root 19-surface-reconstruction growth regime, smooth films can be grown only on substrates tilted toward the [211BAR] direction. This result suggests that a vicinal surface, which is tilted toward the [211BAR] direction, may have less surface-free energy than the exact (111BAR) surface. Characterization of superlattices grown on vicinal GaAs(111BAR) substrates, tilted 3-degrees toward the [211BAR] direction, are also presented.