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

Abstract

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 57 Co and 241 Am 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.

Low frequency noise and ions diffusion in the CdTe bulk single crystals

“…However, Schottky -type CdTe detectors have been fabricated to suppress the league current [1][2], it has been showed instability with time under bias voltage and their collection properties degraded on the hour time scale showing polarization effect [2][3][4]. This effect has been observed through many years in CdTe detectors [5][6][7], but its origin is not fully attributed.…”

“…It is clear that the quit low capture cross section evaluated is due to the very long time considered as "detrapping time" in these models. On the other hand, electrode interfaces were showed an effective role on the polarization effect [1,12,13].…”