Pixelated CdZnTe detector based on Topmetal-IIa readout chip

In order to solve the leakage current saturation of Topmetal-II− and to maintain its low noise, Topmetal-IIa has been designed. The new chip has the same Rolling-Shutter module as Topmetal-II−. It contains a charge-collection electrode and a metal layer surrounding it, called guard ring. This new design contains three different sections. Section A has the same structure as Topmetal-II−, in that the electrode is exposed and guard ring is covered by insulating layer. Section B has both electrode and guard ring exposed. Section C has guard ring exposed but electrode covered by insulating layer. Preliminary experiments show that if coupled with CdZnTe detector, Section C of the Topmetal-IIa chip is capable of solving the leakage current saturation. Meanwhile, the electrode receives induced signal. Moreover, the charge induction efficiency is influenced by several parameters, such as thickness of adhesive epoxy resin, collecting electrode size, etc. Thus, the optimization of parameters for induction efficiency is studied by simulations. According to the simulation results, it can be concluded that thinner epoxy resin thickness and bigger anode size contribute to higher induction efficiency.