INVESTIGATION OF SILICON DELTA-DOPED GALLIUM-ARSENIDE USING THE SHUBNIKOV-DE HAAS EFFECT AND THEORETICAL MODELING

We report a detailed study of electron sub-band occupancies and satura tion effects in silicon delta-doped gallium arsenide samples, using Ha ll and Shubnikov-de Haas (SdH) measurements in conjunction with numeri cal modeling. This study extends previous work in two respects. First, the samples, produced by molecular beam epitaxy with a nominal delta doping density of 1x10(13) cm(-2) were examined over a wide range of g rowth temperature (395-710 degrees C) to allow the influence of broade ning of the doping profile to be examined. Second, the numerical model ing method, based on a self-consistent solution of Poisson's and Schro dinger's equations, included directly the influence of DX-like donor l evels, located at 200 meV above the conduction band edge. Excellent ag reement with the individual sub-band occupancies determined by SdH was found far all samples up to a growth temperature of 605 degrees C, wi th the total silicon doping density kept constant and dopant broadenin g as the only adjustable parameter in the fit. Despite the evidence fo r inclusion of DX-like donor levels based on our modeling, all samples showed only a weak persistent photoconductivity effect. This is in co ntrast to uniformly doped bulk GaAs, indicating the different nature o f the DX level in two and three dimensional doping. Above 605 degrees C it was not possible to model sub-band occupancies using a constant t otal doping density, showing that another deactivation mechanism such as autocompensation becomes important.