Diode-type CdTe strip and linear array detectors for gamma-ray detection and imaging

Diode-type CdTe detectors were fabricated in two different approaches for gamma-ray detection and imaging applications. The first type is a monolithic one-dimensional (1-D) detector with segmented n-type strips formed on the p-like CdTe crystal wafer. N-type strips were formed by diffusing indium using an excimer laser annealing process. In another approach, single element diode-type detectors were fabricated by growing an iodine-doped epitaxial layer on the p-like CdTe crystal in a metalorganic chemical vapor deposition system working at a low substrate temperature. A 1-D linear array detector was then developed by mounting a number of such small element detectors in a row. Both types of detectors exhibited good diode-like property with suppressed leakage currents in the reverse bias direction, which enabled us to apply a high electric field on the detectors in order to improve their performance. Nuclear detection tests performed at room temperature using ⁵⁷Co and ²⁴¹Am radioisotopes showed improved and uniform spectral responses from both types of detectors. Details about the detector fabrication and the spectral results that demonstrate the imaging and spectroscopy capabilities of these detectors are presented.