Molecular-beam epitaxy on exact and vicinal GaAs(111) substrates

GaAs films grown on exact (1̄1̄1̄) substrates in the √19 ×√19 reconstruction regime always show facets. The facets are composed of vicinal surfaces which are inclined by small angles (∼2°) from the exact (1̄1̄1̄) 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 [112̄], [2̄11], and [12̄1] directions. In the √19 ×√19-surface-reconstruction growth regime, smooth films can be grown only on substrates tilted toward the [21̄1̄] direction. This result suggests that a vicinal surface, which is tilted toward the [21̄1̄] direction, may have less surface-free energy than the exact (1̄1̄1̄) surface. Characterization of superlattices grown on vicinal GaAs(1̄1̄1̄) substrates, tilted 3° toward the [21̄1̄] direction, are also presented.