Pressure-induced Hall-effect spectroscopy of silicon DX states in planar doped GaAs-AlAs superlattices

To determine the energetical separation between the silicon DX states in AlₓGa_1-xAs compounds, we used planar doped GaAs-AlAs superlattices and we tuned the conduction miniband energy by applying hydrostatic pressure. When pressure is applied, the miniband energy crosses over the deep levels while shallow levels are linked to the miniband. Hall measurements performed on selectively doped superlattices allow us to derive the ionization energies of the silicon donor in the framework of the DX-donor model with negative correlation energy. We found four deep states energetically separated one from the other by about 40 meV.