Nucleation and defect generation in lattice matched and mismatched heteroepitaxial layers in the GaAs/AlxGa1−xP/Si system

Abstract

The heteroepitaxial growth of GaAs on Si substrates at 700 °C using Al_xGa_1−xP buffer layers grown at 900 °C by metalorganic chemical vapor deposition is studied using transmission electron microscopy. This GaAs/Al_xGa_1−xP/Si system is unique in that it allows one to study separately the influence of lattice‐mismatch (GaAs/Al_xGa_1−xP) and polar/nonpolar (Al_xGa_1−xP/Si) effects on the heteroepitaxial growth of compound semiconductors. Island‐type nucleation is observed for both effects acting independently, though three‐dimensional growth due to the polar/nonpolar effect (Al_xGa_1−xP/Si) can be suppressed by increasing the Al content (x>0.2) of the Al_xGa_1−xP layers. The nucleation of the GaAs appears to be modified by the nature of the Al_xGa_1−xP buffer layers, i.e., whether they are in the form of islands or planar layers. Single‐crystal, 3‐μm‐thick layers of GaAs can be grown directly at 700 °C on the Al_xGa_1−xP buffer layers without resorting to a two‐step technique. This result demonstrates that purely lattice‐mismatch or polar/nonpolar effects cannot disrupt the crystallinity of the compound semiconductor layer. The surface morphology as well as the nature of defects generated in the 3‐μm‐thick GaAs films can be correlated to the nucleation mode of the GaAs.