IR Photodetectors Based on Isoperiodic Epitaxial Layers of Lead Tin Chalcogenides

Abstract

IR photodetectors have been made on Pb/δ-layer/p-Pb_{1 –x}Sn_xTe_{1 –y}Se_y/p⁺-Pb_0.8Sn_0.2Te/Au and Au/δ-layer/n-Pb_{1 –x}Sn_xTe_{1 –y}Se_y(BaF₂)/Pb surface-barrier structures prepared by liquid-phase epitaxy and thermal evaporation. At ~170 K, peak wavelength λ_p ~ 7.9–8.2 μm, and cutoff wavelength λ_c ~ 8.2–8.5 μm, the former surface-barrier structure has product R₀A (where R₀ is the zero-bias differential resistance and A is the active surface area) = 0.31–0.97 Ω cm², peak quantum efficiency η_λ = 0.32–0.48, and specific detectability \(D_{\lambda }^{*}\) = (0.72–1.83) × 10¹⁰ cm Hz^1/2 W^–1. For photodiodes made on the latter surface-barrier structure, these parameters measured at ~80 K are R₀A = 1.71–2.72 Ω cm², η_λ = 0.34–0.49, and \(D_{\lambda }^{*}\) = (3.02–4.51) × 10¹⁰ cm Hz^1/2 W^–1 at λ_p ~ 8.6–12.3 μm and λ_c ~ 9.2–12.9 μm.