High structural quality Ga1−xInxSb/InAs strained-layer superlattices grown on GaSb substrates

Abstract

Strained Ga1−xInxSb/InAs superlattices exhibiting a high degree of structural perfection have been grown on GaSb substrates. The superlattices display ideal, defect-free structure, to within the resolution limits of transmission electron microscopy (TEM) and high-resolution x-ray diffraction. Cross-sectional micrographs reveal the layers to be highly planar, regular, and coherently strained to the GaSb substrates. No crystalline defects were observable by TEM, despite an internal lattice mismatch of almost 2%. Planarity of the layers is confirmed by the presence of Pendellösung fringes in high-resolution x-ray diffraction, while the observation of numerous sharp satellite peaks indicates little or no interdiffusion within the superlattices. Observed x-ray diffraction is closely fit by simulations based on a kinematical model which accounts properly for the highly strained interfaces and absence of strict translational symmetry in the superlattice growth direction. Based on this fit, an InSb-rich character is assigned to the interfaces, yielding superlattice layer thicknesses and compositions that are in quantitative agreement with those derived from independent growth rate calibrations.