Dislocation microstructures on flat and stepped Si surfaces: Guidance for growing high-quality GaAs on (100) Si substrates

Type-I dislocations at the GaAs/Si interface are beneficial because they effectively relax the mismatched stress, but do not propagate into the GaAs film. Accordingly, the best way to grow a low defect density GaAs film on a Si substrate is to form as many as possible type-I dislocations or, equivalently, to suppress other kinds of defects. The high-resolution transmission electron microscopy study shows that most of the type-I dislocations are formed at the double step on a Si surface. It is further determined that the silicon surface steps are mainly due to the substrate tilting instead of the heating before growth. Based on our study, the (100) Si substrate with double steps along both [110] and [11̄0] axes provides the best condition for growing low defect density GaAs on Si substrates.