IR photodetectors based on isoperiodic epitaxial layers of lead tin chalcogenides

IR photodetectors have been made on Pb/$\delta$-layer/$p$-Pb$_{1-x}$Sn$_{x}$Te$_{1-y}$Se$_{y}/p^{+}$-Pb$_{0.8}$Sn$_{0.2}$Te/Au and Au/$\delta$-layer/$n$-Pb$_{1-x}$Sn$_{x}$Te$_{1-y}$Se$_{y}$(BaF$_{2}$)/Pb surface-barrier structures prepared by liquid-phase epitaxy and thermal evaporation. At $\sim$ 170 K, peak wavelength $\lambda_{p}\sim$ 7.9–8.2 $\mu$m, and cutoff wavelength $\lambda_{c}\sim$ 8.2–8.5 $\mu$m, the former surface-barrier structure has product $R_0 A$ (where $R_0$ is the zero-bias differential resistance and $A$ is the active surface area) = 0.31–0.97 $\Omega$ cm$^2$, peak quantum efficiency $\eta_\lambda$ = 0.32–0.48, and specific detectability $D_{\lambda}^*$ = (0.72–1.83) $\times$ 10$^{10}$ cm Hz$^{1/2}$ W$^{-1}$. For photodiodes made on the latter surface-barrier structure, these parameters measured at $\sim$ 80 K are $R_0 A$ = 1.71–2.72 $\Omega$ cm$^2$, $\eta_\lambda$ = 0.34–0.49, and $D_{\lambda }^{*}$ = (3.02–4.51) $\times$ 10$^{10}$ cm Hz$^{1/2}$ W$^{-1}$ at $\lambda_ p\sim$ 8.6–12.3 $\mu$m and $\lambda_ c\sim$ 9.2–12.9 $\mu$m.