Abstract
The atomistic nature of the deep donor levels referred to as DX centers in GaAs, Al x Ga 1- x As alloys and AlAs/GaAs superlattices is investigated by applying the ab initio self-consistent pseudopotential method to 64-atom super cells. The total energy and force calculations reveal that the most stable state is the T d -distorted atomic configuration around a substitutional donor with the neighbouring bond relaxation given by the effective ionic radius (0.7% for Si G a ). On the contrary, a negatively charged donor with broken-bond configuration is shown to give a metastable state and not the ground state even under high hydrostatic pressures. It is found that a deep A 1 level attributable to the DX center is induced by a simple substitutional donor with the obtained optimal lattice configuration. The theory successfully explains experimental results on the thermal and optical ionization energies for the DX centers.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have