Surface-barrier photoconverters with graded-gap layers in the space-charge region

A novel possibility of controlling the parameters of $p$-Cu$_{1.8}$S–$n$-A$^{\mathrm{II}}$B$^{\mathrm{VI}}$ surface-barrier structures by embedding a thin graded-gap layer into a photoconverter space-charge region (SCR) is implemented. The feature of quasi-electric fields built in the SCR, i.e., the fact that an increase in the drift field for minority carriers can be accompanied by a decrease in the potential barrier for majority carriers, is considered. The proper choice of the parameters of the Cd$_x$Zn$_{1-x}$S graded-gap layer embedded in the Cu$_{1.8}$S–ZnS structure SCR made it possible to double the quantum efficiency in the ultraviolet spectral region. For Cu$_{1.8}$S–ZnS photoconverters with a (CdS)$_x$(ZnSe)$_{1-x}$ intermediate layer, dark diode currents are decreased by three orders of magnitude while retaining a high quantum efficiency.