Gamma Response of Semi-insulating Material in the Presence of Trapping and Detrapping

Abstract

The photoelectric and Compton response to γ rays for a detector made from semi-insulating material (i.e., a monocrystalline semiconductor containing trapping centers) was calculated for the case of charge transport by one type of carrier (electron or hole), and also for the case of two-carrier transport (electron and hole) with each carrier having the same mean free path. Approximate expressions were then derived for the observable γ-ray efficiency of the detector as a function of material parameters for CdTe crystals used in the fabrication of surface barrier detectors; this efficiency is dependent upon temperature and electric field intensity for specified values of the carrier mobility-trapping time product and the threshold used in the recording of spectra. Spectra and values for efficiency were determined at room temperature for γ rays at energy values from 0.393 to 1.33 MeV, and also as a function of temperature over the range 24° to 68°C for γ rays from a 60Co source. The observations show behavior corresponding to a trap-limited response, and the presence of charge detrapping.

Transport properties and spectrometric performances of CdZnTe gamma-ray detectors

“…Next we consider the dependency of the efficiency of charge collection from the transport parameters of electrons and holes in the planar detector irradiated by gamma-quanta from the negative contact [1] ( ) …”

“…The absorbed energy E i is converted into the charge value using the mean energy of generation of an electron-hole pair, ε. Our assessments of the charge-collection efficiency, CCE, in the planar detectors are made using the basic Hecht model [1] . Controlling the model's parameters also are important in measuring channel characteristics: pulse shaping time, equivalent noise charge and the width of the analog-digital converter (ADC) channel.…”

“…Such investigations can be relatively easy when carried out with planar detectors for which the Hecht equation can describe the relationship between the CCE and the mean free paths of charge carriers λ e,h . [1] Experiments showed [2] that in CdZnTe single-crystals, the ratio of charge transport parameters for electrons and holes within the same ingot may vary profoundly: (µτ) e /(µτ) h = 10…100 (µ -mobility and τ -average life time of the charge carrier). Furthermore, modification of the ingot's (µτ) e,h product can be due to technological processing of the material during manufacturing into a detector, or may result from the accumulation of defects during growth or operation [3] .…”

Influence of Fast Neutron Irradiation on Signal Response of CdTe Radiation Detectors

“…1 Pulse height spectra of a CdTe detector for Cs before and after neutron irradiation 137 at the fluence of 4x10' n/cm2 and after that, it became broader with the fluence. The two-dimensional (pulse height-pulse risetime) spectrum of 137Cs gamma-rays is presented in Fig.…”

Gamma-ray imaging and spectroscopy system using room-temperature semiconductor detector elements

“…6. Contour plots of the intensity distribution of the gamma-ray count rate on a CZT orthogonal strip detector.…”