MONOMOLECULAR STEPS OF ULTRA-LOW DENSITY ON (100) GROWTH FACES OF LIQUID-PHASE EPITAXIAL GAAS

Steps of monolayer height, when in low density present on facets of li quid phase epitaxial GaAs, constitute almost atomically flat growth fa ces. We achieve a ratio of monostep spacing to step height as high as 10(6): 1 on (100)-oriented facets. The 2.85 angstrom high monosteps ar range themselves inside closely adjoining square-shaped facets. The de velopment of the facets is initiated by mesas of 0.5 x 0.5 mm2 area, w hich are produced on the substrate prior to epitaxy. The monosteps on the facets appear in spiral or concentric patterns or in arrays of nea rly straight steps. We have correlated the different monostep patterns with their particular step generation mechanism. The monosteps are ma pped by optical and atomic force microscopy.