Raman spectroscopy of doping sheets and heterointerfaces in III-V semiconductor structures

Raman spectroscopy was used to study vibrational modes of Si delta-doping sheets and Si monolayers inserted in GaAs and to investigate mechanical interface modes in InAs/GaSb and InAs/AlSb heterostructures. Increasing the concentration of Si embedded in GaAs in a single layer from 10(exp 12)-10(exp 13) cm(exp -2), corresponding to typical concentrations for Si delta-doping in GaAs, to a monolayer (ML) coverage (1 ML = 6.2 x 10(exp 14) cm(exp -2)) leads to a discontinuous change in the Raman spectrum from local vibrational modes of substitutional Si to a vibrational band at significantly higher wavenumbers. This band has been identified with vibrational modes of two-dimensional clusters of covalently bonded Si embedded in GaAs. In InAs/GaSb superlattices both GaAs-like and InSb-like interface modes were resolved, depending on the intended formation of either Ga-As or In-Sb interface bonds. For InAs/AlSb heterostructures, however, only the InSb-like interface mode was observed, indicatin g the formation of InSb-like interface bonds, irrespective of the intended growth of either In-Sb or Al-As interface bonds.