Study of single and double Si delta-doped GaAs layers by spectral photoconductivity measurements

Low temperature spectral photoconductivity measurements were used to obtain the part of the energy spectrum in the absorption edge region connected wi th the presence of doping donors in single and double Si delta-doped GaAs l ayers. Experimental results proved that, in delta-doped samples with a high concentration of donors and a thin cup layer under illumination in the ban d edge region at low temperatures, optical transitions into the bound excit on states prevail. The potential of the donors in the delta-layer and the d istance between the layers in double doped layers determine the features of the energy spectrum. The free-electron distribution at low temperatures is given by the classical Poisson equation rather than by the model of free 2 D electrons in a V shaped potential. (C) 1999 Elsevier Science S.A. All rig hts reserved.