Surface micro-roughness and transport properties of Si delta-doped GaAs/InxGa1-xAs/GaAs (0.1≤x≤0.25) quantum wells grown by molecular-beam epitaxy on GaAs (001) and GaAs (111)B

Abstract

We investigated the surface quality and electron transport properties of 200 Å GaAs/InxGa1-xAs/GaAs, 0.1≤x≤0.25, quantum well structures grown by molecular-beam epitaxy on GaAs (001) and (111)B, center delta-doped with Si to 1 × 1013 cm-2. For GaAs barriers grown above 600°C, room temperature atomic force microscopy of the (111)B samples showed a surface micro roughness below 2 Å for x≤0.15 but reaching 60 Å for x=0.25. In addition, analysis of Shubnikov-de Haas and Hall effects at 4.2 K showed a strong deterioration of the electrical properties. In contrast, the (001) structures had surface micro roughness below 2 Å and superior transport properties even at x=0.25. At lower growth temperatures the surface morphology roughened, but without a commensurate deterioration of the electrical properties. For the (001) layers self-consistent Poisson-Schrödinger calculations give quantum well subband densities in good agreement with those measured, assuming full incorporation of Si substitutional donors. However, a 20% loss of carriers was observed in the (111) layers, and the excited state subband densities were a smaller fraction of the ground subband occupancy compared to the (001). Amphoteric (Si-on-As sites) behavior is believed responsible for this behavior. © 1999 American Institute of Physics.