Monitoring of carrier lifetime in GaAs substrate–epi-layer structures by space-resolved transient microwave absorption

New techniques of transient microwave absorption and their application for the extraction of recombination parameters of SI GaAs with different doping concentrations and layered n+-epi-GaAs structures are presented. Experimentally obtained decay kinetic shape and lifetime variations indicate multi-centre recombination and trapping effects. In highly doped material the extracted absolute carrier lifetime values of 10–50 ns in the substrate and 300–500 ns in the epi-layer allow the evaluation of the higher quality of the epi-layer. A depth scan of the excess carrier decay in the epi-layer revealed that carrier lifetime values of 1–3 μs measured in the undoped material are nearly homogeneous in the epi-layer, while they decrease towards the epi-substrate boundary.