DEPTH PROFILING OF CARRIERS IN ZNSE/GAAS HETEROSTRUCTURES BY RAMAN-SPECTROSCOPY

Non-intentionally doped ZnSe epilayers grown on (100) semi-insulating GaAs substrates by the MOVPE technique constitute heterostructures exhibiting "apparent" p-type conductivity, which we have investigated by Raman spectroscopy. The Raman spectrum of the substrate gives evidence of the presence of a p-type carrier gas in GaAs with p ranging from 10(18) to 10(20) cm-3, which appears as confined at the interface of ZnSe/GaAs. We have shown that the indium dots used for Hall-effect measurements diffuse through the epilayer up to the interfacial gas and concluded that this one is responsible for the large p-type conductivity of the samples. Moreover a quantitative analysis gives access to the interfacial gas thickness, typically 1000 angstrom.