Analysis of Dislocations in CdZnTe Epitaxial Film with Kelvin Probe and Conductive Atomic Force Microscopy

Abstract

The correlation between threading dislocations and leakage current in a CdZnTe(001)/GaAs epilayer grown by close-spaced sublimation was studied using scanning electron microscopy, Kelvin probe force microscopy, conductive atomic force microscopy (C-AFM) and current–voltage (I–V) systems. The electrostatic potential differences between the charged dislocations and the CZT epitaxial film were found to be lower than those in bulk CZT crystal. C-AFM tests in the CZT epitaxial film under forward bias demonstrated that dislocations guided the high current leakage paths. The leakage current at dislocation sites was found to be two orders higher than that at dislocation-free areas with an applied bias of 5 V. The rapid increase in leakage current under applied bias in the range of 3.5–7.5 V was associated with the Poole–Frenkel effect, where high leakage current arises from the high density of trapped carriers escaping from the traps segregated around dislocations.