Improving Energy Resolution of CdSe-Based γ-Ray Detectors through Asymmetric Schottky Contact Engineering Using Oxygen Plasma Treatment

When creating a Schottky contact to suppress the leakage current of semiconductor γ-ray detectors and improve their energy resolution, it is successfully employed the fact that the formation of a Schottky barrier is determined not only by the difference in the electrode and semiconductor work functions but also affected by the semiconductor surface state. Oxygen plasma (OP) treatment has been used to modify the surface states of CdSe single crystals (SCs) prior to the Au electrode deposition, thereby creating a Schottky contact at the metal-semiconductor interface. The <i>n</i>-type Schottky contact formation has been confirmed by the <i>I</i>-<i>V</i> characteristics and ultraviolet photoelectron spectroscopy analysis. X-ray photoelectron spectroscopy has shown that the stoichiometric state of the CdSe SC surface changes from a Cd-deficient (untreated surface) to a near-ideal stoichiometric (OP-treated surface). In addition, a newly formed CdSeO₃ component has been revealed, which is beneficial for suppressing the surface leakage current. The Au/CdSe/Au radiation detector with the single-sided OP-treated surface (Schottky diode) exhibits a higher energy resolution of (23.93 ± 0.89)% for ²⁴¹Am 59.5 keV γ-rays compared to that of the detectors without surface treatment ((44.66 ± 2.25)%). The energy resolution of the champion CdSe-based Schottky diode type γ-ray detector for ²⁴¹Am 59.5 keV γ-rays can reach 22.72%.