CROSSOVER FROM A 2-DIMENSIONAL TO 3-DIMENSIONAL ELECTRONIC-STRUCTURE IN SI SPIKE DOPED GAAS SUPERLATTICES

Periodically Si spike doped GaAs with the doping period in the range 1 00-830 angstrom was studied by magnetoresistance measurements in tilte d fields and by photoconductivity. The angular dependence of the Shubn ikov-de Haas oscillations, in conjunction with a self-consistent calcu lation of the miniband structure is used to construct the Fermi surfac e. When the doping period decreases, the superlattice potential weaken s, and the magnetic breakdown of the superlattice Bragg reflection can be detected. Photoconductivity spectra are described by an absorption threshold at the Fermi energy, which is pushed upwards when the super lattice period decreases.