Photoelectric converters with graded-gap layers based on ZnSe

Oriented polycrystalline CdSe layers are used as substrates for the epitaxial growth of ZnSe. In order to exclude the formation of defects due to mismatch between lattice constants of the active epitaxial layer and the substrate material, a graded-gap Cd$_x$Zn$_{1-x}$Se interlayer is grown. In this structure, the growth of donor-type point defects from the substrate through the growing layers leads to the appearance of a low-resistivity ZnSe layer. A barrier-forming $p$-Cu$_{1.8}$S layer is deposited onto the ZnSe. In order to reduce the recombination losses of photocarriers at the $p$-Cu$_{1.8}$S–$n$-ZnSe interface of the surface-barrier converter, an additional thin graded-gap layer incorporated into the space-charge region of the photoelectric converter is suggested and implemented.