Spatial correlation effects in the charged impurity distribution on the electronic properties of δ-doped structures

In this paper we will show that the -doped GaAs/AlGaAs/GaAs quantum barrier is an ideal system to study deep centers in narrow doping layers with high doping density. By varying the Al content in the barrier, the distance between the Fermi-level and the deep level can be tuned and therefore the number of populated states. By applying hydrostatic pressure this number can be further increased. Our measurements show that in these -doped barrier structures electrons are trapped under hydrostatic pressure and that the quantum mobility is enhanced. This mobility enhancement can be explained by MC calculations which include the effect of the spatial correlation of the charge distribution when the deep state is the DX center and has a negative charge state. The fact that we do not observe a PPC effect or a significant change in the mobility after illumination at high pressure suggest that the Fermi-level is pinned by a non-metastable deep state like the A1 state or that the DX center is modified.