864 Schlesinger, Brunett, Yao, VanScyoc, James, Egarievwe, Chattopadhyay, Ma, Burger, Giles, El-Hanany, Shahar, and Tsigelman 864 Special Issue Paper Journal of Electronic Materials, Vol. 28, No. 6, 1999 (Received November 2, 1998; accepted January 15, 1999) INTRODUCTION Cadmium zinc telluride (CZT, Cd 1–x Zn x Te) has proven to be an important material for the fabrication of room temperature nuclear detectors and spectrometers. Indeed systems based on CZT detectors and detector arrays have been fabricated and have been demonstrated in applications including astronomy, medicine, and national security. 1 Nonetheless, much of the potential of these systems has not been realized due to the high cost of the CZT or the limited availability of large volume samples that may be required in many applications. Both of these problems are a consequence of the low yield of suitable CZT material. The primary growth method used for the production of CZT, to date, is high pressure Bridgman (HPB). Material of high resistivity, low structural and microscopic defect concentrations has been produced, however, large volume samples of HPB material with the properties required is rare and Large Volume Imaging Arrays for Gamma-Ray Spectroscopy T.E. SCHLESINGER, 1 B. BRUNETT, 1 H. YAO, 2 J.M. VANSCYOC, 2 R.B. JAMES, 2 S.U. EGARIEVWE, 3 K. CHATTOPADHYAY, 3 X.-Y. MA, 3 A. BURGER, 3 N. GILES, 4 U. EL-HANANY, 5 A. SHAHAR, 5 and A. TSIGELMAN 5 1.—Carnegie Mellon University, Pittsburgh, PA. 2.—Sandia National Laboratories, Livermore, CA. 3.—Fisk University, Nashville, TN. 4.—West Virginia University, Morgantown, WV. 5.—IMARAD Imaging Systems Ltd., Rehovot, Israel We report for the first time on the characteristics of large volume (4 cm × 4 cm × 0.5 cm) cadmium zinc telluride gamma-ray imaging arrays produced by IMARAD Imaging Systems. These arrays are shown to posses high uniformity of response to gamma-photons in the energy range of about 50 to over 600 keV. High resolution photopeaks have been obtained without any pulse processing or compensation techniques. Excellent peak-to-valley ratios, good efficiencies, and acceptable leakage currents have been measured. In addition measurements of the internal electric field indicate that the field is uniform and does not appear to be confined to only one region of the detector volume. Low temperature photoluminescence spectroscopy shows that the dominant peaks are different than those typically observed in high quality HPB material of the same composition obtained from other vendors. We believe that this material and the arrays that may be produced from it represent a significant step forward in the technology of room temperature semiconductor gamma and x-ray spectrometers. Key words: Bridgman, cadmium zinc telluride CZT), imagers, large volume arrays problems with uniformity make it necessary to spend considerable effort on selecting material. In addition, great effort has been devoted to the development of pulse processing and compensation techniques or the fabrication of electron only devices 2,3 and associated electronics to overcome the problems of hole trapping and thus produce detector systems capable of providing high resolution. In this paper, we report on CZT material produced by a modified horizontal Bridgman technique. This technique has successfully produced large volumes of CZT material which is shown to produce detectors which provide good resolution and uniformity of performance without pulse processing and compensation techniques in a simple pixellated array geometry. In this paper, we do not discuss the mechanism that is proposed for the improved charge collection though one model has been proposed by Lachish. 4 CRYSTAL GROWTH The Cd 1–x Zn x Te (0.12 > x > 0.04) crystals were grown by means of a modified horizontal Bridgman