DX CENTERS IN ALAS AND GAAS-ALAS SELECTIVELY DOPED SUPERLATTICES

DX centers have been investigated using deep level transient spectroscopy (DLTS) in Si doped AlAs and in the selectively doped GaAs-AlAs superlattices (SLs) grown by molecular beam epitaxy. The activation energy for thermal emission is E(a) = 0.42 eV in both the SLs and AlAs layers. For the first time a study of the capture in a SL reveals a capture activation energy E(cap) = 0.36 eV, which locates the DX at E(t) almost-equal-to 60 meV below the conduction miniband. Taking into account the measured energies and trap concentrations, we show that the DX observed in the SLs lies in the AlAs layers.