Study of the Effects of Edge Morphology on Detector Performance by Leakage Current and Cathodoluminescence

Abstract

The Vertical Gradient Freeze (VGF) method has been used to grow high resistivity Cadmium Zinc Telluride (CZT) for high energy radiation applications. In this work, the effect of lapping and polishing the lateral edges of planar detectors is studied. Expectations that improved surface morphology of the edges should correlate with reduced surface leakage current are shown to be erroneous. The effect of various types of lateral edge treatments on detector performance was observed before and after each surface modification. Complementary results were obtained using I-V, Cathodoluminescence (CL), and gamma ray response measurements using 133Ba. As a result, a quick and easy method is reported which minimizes leakage current and actually enhances detector performance through the introduction of surface defects. It is demonstrated that the introduction of radiative recombination centers helps reduce surface leakage current in the detector by a factor of up to 200%, depending on the surface treatment. The purpose of this work is to identify material processing steps for fabricating planar devices based on CZT for gamma ray spectroscopy.

Effect of superheating and fast cooling on Te inclusions of Cd0.9Zn0.1Te:In crystals grown by vertical gradient freezing

“…Three Cd 1-x Zn x Te ingots (x ¼10%) were grown by the Vertical Gradient Freeze (VGF) method using a 5-zone furnace [15].…”

Investigation of crystal growth of 50 mm CZT using SiC pedestal and pBN crucible

“…Devices used in this work have been contacted with Au using the electroless method. Further details regarding detector preparation and measurement may be found in [6][7][8].…”

“…Following these ideas, the work presented here is the result of several experiments whose geometries and materials have been chosen due to their thermal properties. The experimental geometries and materials used in this work are based on extensive simulation studies presented by [1][2][3][4][5][6], in which the materials used to modify the thermal environment to facilitate the crystal growth process are presented. Specifically, the implementation of a Silicon Carbide (SiC) ampoule support pedestal in conjunction with the pBN crucible geometry lead to an increase in the axial heat flow, a decrease in radial heat flow, and improved temperature gradients at the crucible tip.…”

Influence of carbon coated pBN crucible on crystal growth of Cd0.9Zn0.1Te for radiation detector applications

“…Carrier type of the devices has been determined using the hot probe method. The fabrication of planar test devices used in this work follows the methods presented by Crocco et al [12].…”