DX centers in GaAs/Si-δ/AlAs heterostructure

Abstract

Microscopic mechanisms of impurity spreading in GaAs/Si-δ/AlAs heterostructure have been investigated using an ab initio pseudopotential total energy calculation. Our results showed that silicon atoms can move from the δ-doped plane occupying interstitial positions, favored by the high doped concentration, forming DX centers. The silicon impurity position, out of the δ plane in the AlAs layers, presents an energetically stable configuration, and in the GaAs layers, presents a metastable configuration. As a consequence a silicon doping limit is reached due to the presence of localized deep states inside the band gap, when silicon atoms are in interstitial positions.