ELECTRONIC-STRUCTURE OF A SI DELTA-DOPED LAYER IN A GAAS ALXGA1-XAS/GAAS QUANTUM BARRIER/

We present a theoretical study of the electronic structure of a heavil y Si delta-doped layer in a GaAs/AlxGa1-xAs/GaAs quantum barrier. In t his class of structures the effect of DX centers on the electronic pro perties can be tuned by changing the AlxGa1-xAs barrier width and/or t he Al concentration, which leads to a lowering of the DX level with re spect to the Fermi energy without disturbing the wave functions much. A self-consistent approach is developed in which the effective confine ment potential and the Fermi energy of the system, the energies, the w ave functions, and the electron densities of the discrete subbands hav e been obtained as a function of both the material parameters of the s amples and the experimental conditions. The effect of DX centers on su ch structures at nonzero temperature and under an external pressure is investigated for three different models: (1) the DX(nc)(0) model with no correlation effects, (2) the d(+)/DX(0) model, and (3) the d(+)/DX (-) model with inclusion of correlation effects. In the actual calcula tion, influences of the background accepters, the discontinuity of the effective mass of the electrons at the interfaces of the different ma terials, band nonparabolicity, and the exchange-correlation energy of the electrons have been taken into account. We have found that (1) int roducing a quantum barrier into delta-doped GaAs makes it possible to control the energy gaps between different electronic; subbands; (2) th e electron wave functions are mon spread out when the repellent effect of the barriers is increased as compared to those in delta-doped GaAs ; (3) increasing the quantum-barrier height and/or the application of hydrostatic pressure are helpful to experimentally observe the effect of the DX centers through a decrease of the total free-electron densit y; and (4) the correlation effects of the charged impurities are impor tant for the systems under study.