A First Principles Method to Simulate the Spectral Response of CdZnTe-Based X- and Gamma-Ray Detectors

Detectors based on compound semiconductor materials like CdTe and CdZnTe are more susceptible to defect-related spectral distortions than elemental semiconductors like Si or Ge. During the design process of new detectors based on these materials it is crucial to consider the effect of these distortions on the detector performance. Due to the diverse range of application areas in which these detectors may be used, the detector geometry must be selected to match the desired application of the device. For those requiring the detection of photons across a broad energy range (1 - 1000 keV), the detector design must account for a variety of different interaction processes. The simulation framework presented in this paper includes all the physical processes involved in the formation of the detector signal, from the radiation absorption mechanisms to the influence of the electrode geometry. A simulation system based on first principle calculations is used which consists of a Monte Carlo simulator, a Finite Elements Method (FEM) calculator and numerical computation software. The framework simulates the radiation-semiconductor interaction, the charge carrier transport and the role of the electric field and weighting field in signal induction on the electrodes. This tool allows to simulate the entire experimental arrangement including the use of attenuators, collimators and scattering surfaces. The ability to accurately simulate the detector response to radiation and its surroundings provides a powerful tool for the realization of a new generation of detector systems. In order to validate the simulation framework, CdZnTe-based detectors with several contact geometries have been modelled and the output of the simulations have been compared to experimental data. A comparison between the simulated and measured responses demonstrate the power of this technique.