Study of Structural Defects in Ternary Chalcopyrite Semiconductors by Positron Annihilation Spectroscopy and Photoluminescence Spectroscopy

Abstract

This thesis reports results of positron lifetime, Dopple1-broadening,

photoluminescence and X-ray investigations to study the fundamental nature of I point defects in CulnS2, CulnSe2, AglnS2 and AglnSe2 semiconductors and, for I the first time, provides direct evidence of the charge state of the defect

configuration. The results of Hall effect are also presented for det rmining the carrier concentration and type with the aim to follow up the changes of Fermi level affecting the positron lifetime. The I-III-VI2 (I = Cu, Ag, III =In, and VI = I S, Se) bulk crystals were grown using a direct fusion technique folloWed by slow directional solidification. The whole growing process took about 114 - 22 days I ensuring crystals of very high quality. The Rietveld method for structure

refinement was used to study the synthesised samples. PositroJ states and I annihilation rates were also calculated. The calculations were based on the

generalized gradient approximation (GGA) for the electron-positron correlation effects.

Kevwords: Chalcopyrite Semiconductors, Positron Lifetime, Hall

Measurements, Photoluminescence, Defects