Be Delta-Doped Layers in GaAs Imaged with Atomic Resolution Using Scanning Tunneling Microscopy

We present first results of the analysis of molecular beam epitaxy-grown Be:GaAs delta-doped layers with atomic resolution using cross-sectional scanning tunneling microscopy. At low Be areal density, the width of the delta layers is 1 nm, whereas at higher Be areal densities the spreading of the layers to approximately 5 nm is appreciable. Most of this spreading is symmetric around the intended position of the delta-doped layer, and is ascribed to drift resulting from the Coulombic repulsion between the ionized dopants at growth temperature. Structure in the spatial distribution function of dopants within the delta layer also reflects this repulsion.