Characterization of Fine-Pixel X-Ray Imaging Detector Array Fabricated by Using Thick Single-Crystal CdTe Layers on Si Substrates Grown by MOVPE

Abstract

A novel approach for developing a large area, high-spatial-resolution X-ray imaging detector is presented. This approach uses metal–organic vapor phase epitaxy grown thick single-crystal CdTe layers grown directly on Si substrates. The detector consists of a p-CdTe/n-CdTe/n+-Si heterojunction diode structure, where the n-CdTe and the p-CdTe layers are successively grown on the n+-Si substrate. An array of ( $128\times128$ ) pixels was formed on the p-CdTe side, where each pixel is $60~\mu \text{m}^{\textsf {2}}$ in an 80- $\mu \text{m}$ pixel pitch. The detector array was bump bonded to a charge integration-type CMOS readout ASIC. The basic performance of this detector was evaluated by measuring the dark currents, the X-ray generation currents as well as taking the X-ray images of some objects. The results were promising which confirmed that the detector developed can be applied in high spatial resolution X-ray imaging.