Suppression of D X centers in GaAlAs-GaAs heterostructures

Abstract

Using deep level transient spectroscopy we have studied the DX center in a series of periodic GaAs/GaAlAs uniformly Si doped structures. The presence of the DX center is only detected when the structures do not exhibit superlattice behavior. This is understood by the fact that either the DX associated level is resonant in the first conduction miniband (or above it) or that it does not exist because the original band structure of GaAlAs is destroyed by electron delocalization. Examination of the variation of the concentration of DX centers in periodic planar doped GaAlAs structures shows that this disappearance is due to a band structure effect, thus demonstrating that the DX center originates from a shallow-deep instability of the L-band effective mass state of the Si impurity due to intervalley mixing.