DEEP-LEVEL CHARACTERIZATION IN SEMIINSULATING GAAS BY PHOTOINDUCED CURRENT AND HALL-EFFECT TRANSIENT SPECTROSCOPY

Deep levels in semi-insulating (SI) GaAs single crystals were studied by photo-induced current transient spectroscopy (PICTS) and photo-indu ced Hall effect transient spectroscopy (PHETS). A method of measuring the defect level density using PHETS was developed and used to measure the EL6 density in SI-GaAs. Investigations were made into EL2 and EL6 , the main defect levels in SI-GaAs, to find the density distribution in the as-grown wafer and the annealing behaviour in the temperature r ange from 600 to 1100 degrees C. The density distribution of EL2 acros s the wafer showed a so-called W-shaped pattern similar to the disloca tion density, but the EL6 distribution showed an M-shaped pattern. Ann ealing at temperatures from 800 to 1000 degrees C increased the densit y of each level, whereas annealing at 1100 degrees C diminished it. Th ese experimental results were well explained by tentative defect model s for EL2 (AsGaVGa) and EL6 (AsGaAsi).