M ar 1 99 7 Electronic States in Diffused Quantum Wells

In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, sp 3 s * spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengths L D =20 ÷ 100Å the transition (C3 − HH3) is not sensitive to the diffusion length, but the transitions (C1 − HH1), (C1 − LH1), (C2 − HH2) and (C2 − LH2) display large " blue shifts " as L D increases. For diffusion lengths L D =0 ÷ 20Å the transitions (C1 − HH1) and (C1 − LH1) are less sensitive to the L D changes than the (C3 − HH3) transition. The observed dependence is explained in terms of the bound states spatial distributions .