Preparation of Cd_0.8Zn_0.2Te/Cd_0.5Zn_0.5Te/n⁺-GaAs thick film radiation detectors by close spaced sublimation

High quality Cd_0.8Zn_0.2Te epitaxial films with a Cd_0.5Zn_0.5Te buffer layer on n⁺-GaAs(001) substrates were prepared using a modified close spaced sublimation (CSS) furnace. The effects of the Cd_0.5Zn_0.5Te buffer layer on crystalline quality and electric properties on Cd_0.8Zn_0.2Te films were studied using double crystal X-ray rocking curve (DCXRC), atomic force microscope (AFM), scanning electron microscope (SEM), current-voltage (I–V) measurements, and energy spectra tests. The Cd_0.5Zn_0.5Te buffer layer improved the crystalline quality of a thinner Cd_0.8Zn_0.2Te film (2 μm) but had less effect on a thick Cd_0.8Zn_0.2Te film (200 μm). The I–V results showed that the electron injection from n⁺-GaAs to the Cd_0.8Zn_0.2Te film can be restrained by the Cd_0.5Zn_0.5Te buffer layer. Meanwhile, the existing of the Cd_0.5Zn_0.5Te buffer layer effectively reduced the electronic noise in the spectra tests. Consequently, the modified multi-layer film detector with the Au/Cd_0.8Zn_0.2Te/Cd_0.5Zn_0.5Te/n + -GaAs/Au structure showed a considerable resolution of approximately 18% for ²⁴¹Am@59.5 KeV γ-ray.