GENERATION AND ANNIHILATION OF ANTIPHASE DOMAIN BOUNDARIES IN GAAS ONSI GROWN BY MOLECULAR-BEAM EPITAXY

A comprehensive investigation of antiphase domain boundaries (APB's) i n GaAs-on-Si is presented. A comprehensive experimental approach, base d on complementary electron microscopy (TEM and SEM) and chemical etch techniques, is developed and used in the study of the structural evol ution of APB's on vicinal (001)Si substrates. The question of whether a GaAs selective nucleation or APB annihilation accounts for the absen ce of APB's in thick GaAs/Si films, grown on substrates misoriented fr om (001) toward [110], is addressed. APB's are revealed by two differe nt TEM techniques to exist in the first interfacial layers of GaAs/Si even in samples considered to be ''APB free''. The APB annihilation me chanism is illustrated in GaAs films grown on substrates misoriented t oward [100], either directly, by cross-sectional TEM observations, or indirectly, by combined chemical etch/SEM experiments. In addition, th e structural characteristics of APB's and their interaction with other extended crystal defects are clarified by XTEM and TEM observations. Finally, the influence of APB's on GaAs/Si surface morphology and thei r electrical activity are shown explicitly for the first time.