DXcenter: Crossover of deep and shallow states in Si-dopedAlxGa1xAs

Abstract
A new microscopic model for the origin of the DX center in Si-doped Alx Ga1xAs is proposed based on discrete variational cluster calculations. The calculated level structure shows that the antibonding A1 state of Si, which lies in the conduction bands as a resonance state in the case of GaAs, shifts downwards into the energy gap upon distortion of the neighboring four As atoms in the case of Alx Ga1xAs. The formation energy of this distorted configuration is estimated from the shift of the level of the antibonding A1 state along with the Keating-model calculation for the lattice distortion energy. As a result, the distorted configuration is found to be stable in Si-doped Alx Ga1xAs.