Besides silicon GaAs is one of the most important materials in modern technology and therefore a method to investigate the material quality is needed. Since GaAs is a direct semiconductor the recombination lifetime is very small and often not detectable by photoconductivity based methods, but slower decays originating from traps as the well-known EL2 can be investigated.

In contrast to other techniques MD-PICTS (microwave detected photo induced current transient spectroscopy) can detect signals even from thin surface regions (3 µm) of SI GaAs samples and is therefore able to analyze e.g. influence of surface treatments. Figure 1 shows the defect peak of the well-known EL2 defect in samples with different acceptor concentrations.