Jm. Shi et al., ELECTRONIC-STRUCTURE OF A SI DELTA-DOPED LAYER IN A GAAS ALXGA1-XAS/GAAS QUANTUM BARRIER/, Physical review. B, Condensed matter, 54(11), 1996, pp. 7996-8004
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.