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

We investigated the surface quality and electron transport properties of 20 0 Angstrom GaAs/InxGa1-xAs/GaAs, 0.1 less than or equal to x less than or e qual to 0.25, quantum well structures grown by molecular-beam epitaxy on Ga As (001) and (111)B, center delta-doped with Si to 1 x 10(13) cm(-2). For G aAs barriers grown above 600 degrees C, room temperature atomic force micro scopy of the (111)B samples showed a surface micro roughness below 2 Angstr om for x less than or equal to 0.15 but reaching 60 Angstrom 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 Angstrom and superior tran sport properties even at x = 0.25. At lower growth temperatures the surface morphology roughened, but without a commensurate deterioration of the elec trical properties. For the (001) layers self-consistent Poisson-Schrodinger calculations give quantum well subband densities in good agreement with th ose measured, assuming full incorporation of Si substitutional donors. Howe ver, a 20% loss of carriers was observed in the (111) layers, and the excit ed state subband densities were a smaller fraction of the ground subband oc cupancy compared to the (001). Amphoteric (Si-on-As sites) behavior is beli eved responsible for this behavior. (C) 1999 American Institute of Physics. [S0003-6951(99)02142-7].