Intermediate band formation in a δ-doped like QW superlattices of GaAs/Al_xGa_(1_x)As for solar cell design

摘要

It is reported a numerical computation of the local density of states for aδ-doped like QW superlattices of AlxGa1−xAs, as a possible heterostructure that, being integrated into a solar cell device design, can provide an intermediate band of allowed states to assist the absorption of photons with lower energies than that of the energy gap of the solar-cell constituent materials. This work was performed using the nearest neighborssp3s*tight-binding model including spin. The confining potential caused by the ionized donor impurities inδ-doped impurities seeding that was obtained analytically within the lines of the Thomas-Fermi approximation was reproduced here by the Al concentrationxvariation. This potential is considered as an external perturbation in the tight-binding methodology and it is included in the diagonal terms of the tight-binding Hamiltonian. Special attention is paid to the width of the intermediate band caused by the change in the considered aluminium concentrationx, the inter-well distance betweenδ-doped like QW wells and the number of them in the superlattice. In general we can conclude that this kind of superlattices can be suitable for intermediate band formation for possible intermediate-band solar cell design.