Investigation of the electronic properties of cadmium zinc telluride (CZT) detectors using a nuclear microprobe

Abstract

The electronic transport properties of Cadmium Zinc Telluride (CZT) determine the charge collection efficiency (i.e. the signal quality) of CZT detectors. These properties vary on both macroscopic and microscopic scales and depend on the presence of impurities and defects introduced during the crystal growth. Ion Beam Induced Charge Collection (IBICC) is a proven albeit relatively new method to measure the charge collection efficiency. Using an ion microbeam, the charge collection efficiency can be mapped with submicron resolution, and the map of electronic properties (such as drift length) can be calculated from the measurement. A more sophisticated version of IBICC, the Time Resolved IBICC (TRIBICC) allows us to determine the mobility and the lifetime of the charge carriers by recording and analyzing the transient waveform of the detector signal. Furthermore, lateral IBICC and TRIBICC can provide information about how the charge collection efficiency depends on the depth where the charge carriers are generated. This allows one to deduce information on the distribution of the electric field and transport properties of the charge carriers along the detector axis. IBICC and TRIBICC were used at the Sandia microbeam facility to image electronic properties of several CZT detectors. From the lateral TRIBICC measurement the electron and hole drift length profiles were calculated.