Development of Large-Area Imaging Arrays Using Epitaxially Grown Thick Single Crystal CdTe Layers on Si Substrates

Abstract

Optimization of CdTe crystal growth by adjusting effective Te/Cd ratio at the growth surface, as well as growth-interrupted annealing together with detector array fabrication techniques were studied to achieve large-area, uniform x-ray spectroscopic imaging arrays. The ${\rm p}\hbox{-}{\rm CdTe}/{\rm n}\hbox{-}{\rm CdTe}/{{\rm n}^ +}\hbox{-}{\rm Si}$ heterojunction diode-type detector arrays were fabricated by using epitaxially grown thick single crystal CdTe layers on ${{\rm n}^ +}\hbox{-}{\rm Si}$ substrates, where pixels were patterned by making deep vertical cuts on p-CdTe side using a dicing saw. The study was first focused on development of 2D ( $8 \times 8$ ) array using $12.6~\hbox{mm} \times 11.4~\hbox{mm}$ size wafers, which confirmed uniform dark current distribution among the pixels. We further demonstrated possibility of making larger arrays by fabricating ( $18 \times 18$ ) array using a $25~\hbox{mm} \times 25~\hbox{mm}$ size uniform single crystal CdTe epilayer grown on Si substrate.