Specific features of the low-temperature conductivity and photoconductivity of CuInSe$_2$–ZnIn$_2$Se$_4$ alloys

n-type CuInSe$_2$–ZnIn$_2$Se$_4$ alloy single crystals are grown by the horizontal variant of the Bridgman method. The slight temperature dependence of the conductivity, high electron concentration, and the low photoconductivity of single crystals containing a low (5–10 mol%) fraction of ZnIn$_2$Se$_4$ are indicative of the nearly degenerate state of the crystals. It is established that, in the CuInSe$_2$–ZnIn$_2$Se$_4$ single crystals containing 15 and 20 mol% of ZnIn$_2$Se$_4$, the hopping mechanism of conductivity is dominant at temperatures of $T\sim$ 27–110 K. At $T\ge$ 110 K, hopping conductivity gives way to activated conductivity. It is found that the specific feature of the low-temperature (27–77 K) photoconductivity spectrum of single crystals with $\sim$ 15 and 20 mol% of ZnIn$_2$Se$_4$ is a single narrow peak at a wavelength of $\lambda_{\mathrm{max}}$ = 1190–1160 nm.