Positron Lifetime Spectroscopy Study Of Defects In Compound Semiconductors

Positron annihilation technique has been effectively used for study of defect particularly of open-volume defects in semiconductors. Since compound semiconductor has potentially numerous applications in high temperature, radiation hard, and high power IC device, the study of defects in compound semiconductors has been increasing using positron annihilation technique.The method of positron lifetime spectroscopy used for study of defect in compound semiconductor has been introduced mainly in this paper. This thesis is composed of three parts:1. The basic processes of positron solid physics and the experimental techniques used in positron annihilation spectroscopy have been introduced, and the method of positron lifetime spectroscopy has been mainly introduced.2. Positron lifetime spectroscopy has been tested, and some optimal parameters has been found, and meanwhile stability of the spectroscopy has been verified.3. Positron lifetime measurements have been carried out in both before andafter electron irradiation n-type 6H-SiC in the range of 20-300K. The results were explained by a proposed model, in which the shifting of Fermi-level affects the defect ionization and consequent positron trapping at defect sites. Some defect lifetime values and their level position have been obtained by fitting the positron lifetime data.