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A theoretical study of the electronic structure of periodically 6doped GaAs Is presented. When the doping period is reduced, minibends are formed, and the photoluminescence spectrum presents a broad emission band at energies above the GaAs band edge. The experimentally obtained photoluminescence lineshape is well reproduced by the theory. The calculated cut-off energy in the photoluminescence spectrum is in excellent agreement with the experimental value. The Fermi surface is studied as a function of the doping period. The gradual change in the Fermi surface, which occurs when the spacing between the dopant sheets decreases, provides a clear-cut description of the crossover from two-to three-dimensional electronic structure in 6-doped GaAs.The response of the system to a magnetic field, applied in t h e plane of the layers, is considered, and the condition of magnetic breakdown is studied.

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Single and periodically Si δ-doped InP layers were grown by LP-MOVPE at 640 • C. A full width at half maximum of 32 Å was obtained for the net charge concentration profile for a sample with a peak net charge concentration of 1.8 × 10 19 cm −3 . Numerical simulations showed that the impurities are localized over less than three InP monolayers. No dopant diffusion or segregation was observed. The periodic structures, grown with barriers varying from 100 to 300 Å, all had nearly the same carrier sheet concentration per dopant layer and impurity localization characteristics.

The quantum and transport subband mobilities as a function of applied bias were calculated for a gated δ-doped semiconductor. The electronic spectra (envelope wavefunctions, subband energies and Fermi energy) for the structure under bias used as input in the calculations were obtained by either solving self-consistently Schr ödinger and Poisson equations or by solving the Schr ödinger equation with a confining potential determined by the Thomas-Fermi semiclassical approximation. In the first case the screening of the electron-ionized impurity interaction was treated in the random phase approximation, whereas in the latter case the two-dimensional Thomas-Fermi model of screening was used. Results show that although the semiclassical approach offers the advantage of greater simplicity, it describes reliably the carrier mobility in the fundamental subband only. The dependence of the mobility of carriers in individual subbands on applied bias correlates with the evolution with bias of the overlap between subband wavefunctions and the doped-layer region.