Preparation of Cd0.8Zn0.2Te/Cd0.5Zn0.5Te/n+-GaAs thick film radiation detectors by close spaced sublimation

Abstract

High quality Cd0.8Zn0.2Te epitaxial films with a Cd0.5Zn0.5Te buffer layer on n+-GaAs(001) substrates were prepared using a modified close spaced sublimation (CSS) furnace. The effects of the Cd0.5Zn0.5Te buffer layer on crystalline quality and electric properties on Cd0.8Zn0.2Te 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 Cd0.5Zn0.5Te buffer layer improved the crystalline quality of a thinner Cd0.8Zn0.2Te film (2 μm) but had less effect on a thick Cd0.8Zn0.2Te film (200 μm). The I–V results showed that the electron injection from n+-GaAs to the Cd0.8Zn0.2Te film can be restrained by the Cd0.5Zn0.5Te buffer layer. Meanwhile, the existing of the Cd0.5Zn0.5Te buffer layer effectively reduced the electronic noise in the spectra tests. Consequently, the modified multi-layer film detector with the Au/Cd0.8Zn0.2Te/Cd0.5Zn0.5Te/n + -GaAs/Au structure showed a considerable resolution of approximately 18% for 241Am@59.5 KeV γ-ray.