Formation of GaAs quantum well islands by thermal desorption using an AlAs mask

Small optoelectronic and electronic devices often suffer from high levels of nonradiative recombination at the surfaces, due to their high surface-to-volume ratios. We propose the use of lateral carrier confinement in the quantum well to prevent diffusion of carriers to the surfaces. We demonstrate a technique for providing this lateral confinement by thermally desorbing portions of a GaAs quantum well using a monolayer AlAs mask. The mask is formed by depositing a fractional monolayer of AlAs in such a way as to form stable islands on the GaAs surface. We present the first direct evidence for the success of this AlAs island masking technique: the desorption of the GaAs quantum well using reflection high energy electron diffraction is observed, and transmission electron microscopy and atomic force microscopy show the resulting GaAs islands to have roughly pyramidal cross-sections, with an average base size of 350 x 150 Angstrom, aligned along the [01 (1) over bar] direction.