Trap distribution in ZnIn₂S₄ from photoconductivity analysis

Photoconductivity, quenching, thermally stimulated current and decay characteristics are studied in ZnIn₂S₄ single crystals. Evidence is obtained for the presence of three impurity levels taking part in the photoconductivity process. Optical quenching is attributed to a sensitization centre, which acts as a competitive recombination level. An exponential distribution of electron traps is revealed both by pulsed photoconductivity and by thermocurrent analysis. The two experimental techniques accordingly provide the value of 70 meV/decade for the trap distribution. Some aspects of the nature of the impurity centres are examined.