Determination of electron-hole pair creation energy in Cd0.9Zn0.1Te0.98Se0.02 quaternary semiconductor for room-temperature gamma-ray detection

We report the first-time measurement of the electron-hole pair (ehp) creation energy (W_ehp) in novel Cd_0.9Zn_0.1Te_0.98Se_0.02 (CZTS) quaternary semiconductor. CZTS in single crystalline form is poised to be the future of large-volume room-temperature gamma-ray detectors due to its excellent compositional homogeneity with highly reduced defects, high-Z (atomic number) constituents, wide bandgap (1.6 eV), and superior charge transport properties. Despite a great deal of study of the material and device properties since its inception, the W_ehp in CZTS has not been measured experimentally. Accurate determination of W_ehp is essential for calibration of the spectrometer and other theoretical calculations. In this study we have used an absolute calibration approach, which is based on an iterative approach that yields the W_ehp as the best-fit parameter. Using a ²⁴¹Am alpha emitting radioisotope and a planar CZTS detector, the W_ehp in CZTS was calculated to be 4.47 eV. The obtained value has been validated by accurately predicting the peak energy for gamma rays emitted by a ¹³⁷Cs source and read by a CZTS detector with different dimensions. The dependences of the calculated W_ehp value on the detector dimensions, type of interaction, and effect of charge trapping are also discussed.