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. Experim entally obtained decay kinetic shape and lifetime variations indicate multi -centre recombination and trapping effects. In highly doped material the ex tracted absolute carrier lifetime values of 10-50 ns in the substrate and 3 00-500 ns in the epi-layer allow the evaluation of the higher quality of th e epi-layer. A depth scan of the excess carrier decay in the epi-layer reve aled that carrier lifetime Values of 1-3 mus measured in the undoped materi al are nearly homogeneous in the epi-layer, while they decrease towards the epi-substrate boundary. (C) 2001 Elsevier Science B.V. All rights reserved .