Technology Commercialization and Partnerships | BSA 12-19: Surface Treatment of CZT Crystals for Passivation and Reduction of Leakage Current

Category: electronics & instrumentation

BSA 12-19: Surface Treatment of CZT Crystals for Passivation and Reduction of Leakage Current

BNL Reference Number: BSA 12-19

Patent Status: U.S. Patent Number 7,001,849 was issued on February 21, 2006

Summary

This invention comprises a method for surface treatment of CZT crystals that will eliminate or reduce surface leakage currents to a level that is presently unattainable using prior art methods. This method for treatment of the surface of a CdZnTe (CZT) crystal provides a native dielectric coating to reduce surface leakage currents and thereby, improve the resolution of instruments incorporating detectors using CZT crystals. This method involves a two step process, etching the surface of a CZT crystal with a solution of the conventional bromine/methanol etch treatment, and after attachment of electrical contacts, passivating the CZT crystal surface with a solution of 10 w/o ammonium fluoride and 10 w/o hydrogen peroxide in water.

Description

CdZnTe (CZT) crystals, particularly Cd(1-x)Zn(x)Te (where x is less or equal 0.5) crystals and preferably Cd(0.9)Zn(0.1)Te crystals, are useful for fabrication of small, portable, room temperature radiation detectors. In a first embodiment of the present invention a method is taught for treating a surface or surfaces of CZT crystals that provides a coating on the crystal surface which will reduce surface leakage currents to a previously unattainable level and thereby provide for improved energy resolution in instruments incorporating CZT crystals processed by this invention. A two step process is disclosed, wherein the surface of a CZT crystal is etched the traditional bromine/methanol etch treatment (5 volume percent (v/o) bromine in methanol solution), and after attachment of electrical contacts the surface of the CZT crystal is passivated, preferably by treatment with a aqueous solution of ammonium fluoride and hydrogen peroxide.

Benefits

This method for reduction of the surface leakage current in CZT crystals improves spectral resolution to a level previously unattainable using prior art methods.

Applications and Industries

Semiconductor radiation detectors are now used in a large variety of fields, including nuclear physics, X-ray and gamma ray astronomy, and nuclear medicine. Their imaging capabilities, good energy resolution, and the ability to fabricate compact systems are very attractive features, in comparison with other types of detectors, such as gas detectors and scintillators. Medical, imaging, nuclear nonproliferation, non-destructive detection, radiation imaging, and homeland security applications.