Kihyun Kim a, Jan Franc b, Aleksey E. Bolotnikov c, Ralph B. James d
a School of Health and Environmental Science, Korea University, Seoul, 02841, Korea
b Institute of Physics, Charles University, Ke Karlovu 5, Prague, 12116, Czech Republic
c Brookhaven National Laboratory, Upton, 11973, NY, USA
d Savannah River National Laboratory, Aiken, 29808, SC, USA
## Abstract
The addition of 2 % of selenium in CdTe and CdZnTe (CZT) exhibited an additional acceptor-bound exciton in photoluminescence (PL). From the PL and inductively coupled plasma mass spectrometer (ICP/MS) analyses, the additional acceptor-bound exciton emission is associated with a Cu impurity in the relatively low-purity (5N) precursor CdSe starting material. In addition, thermal quenching of the acceptor/donor bound exciton emissions do not require a shift to any higher excited states or to the free exciton state. ICP/MS analysis also showed a higher concentration of Sn in CdZnTeSe (CZTS) compared to CdTe and CZT which is known to form a deep level trap at around E
– 0.83 eV. The trapping and de-trapping times indicate that the Sn-related deep trap acts as an electron trapping center. The relatively low electron mobility-lifetime product of CZTS might be correlated with the concentration of Sn in the impure CdSe material. Pulse height spectra using an Eu-152 gamma-ray source was taken for a 2-mm-thick planar CZTS detector. The spectra clearly showed all the expected gamma peaks with energy lower than 344.3 keV.
## Introduction
There is a report that the addition of 2%–7% of selenium in CdZnTe (CZT) reduces the density of structural defects (i.e., fewer and smaller Te inclusions and sub-grain boundary network) compared to CZT, and the Se-doped CZT exhibits improved detector performance due to better charge-transport uniformity [1]. However, the reported mobility-lifetime product of electrons in CdZnTeSe (CZTS) is just 0.9 × 10−4 to 5 × 10−3 cm2/V which is less than CZT [1], [2], [3]. The lower electron mobility-lifetime product in CZTS was attributed to the impurities in the CdSe starting material such as Cr, Fe, Ni, Cu, Sn, and Pb [1]. Nevertheless, the detector performance is comparable with that of CZT for the Frisch-grid detectors used in the study. In a previous report, an improved detector performance was explained in planar detectors by the reduced hole tailing effect due to the enhanced hole mobility-lifetime product in selenium added CZT [4].
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/photoluminescence-of-cdte-and-cdznte-compounds-doped-with-2-selenium.html