Mis capacitors on BaF 2/PbSe layers and epitaxial Si/BaF 2/PBSE structures for IR detection

Epitaxial BaF ₂ grown by vacuum deposition has been investigated as: (a) an insulating layer in MIS capacitors on narrow-gap semiconducting PbSe (111)-surfaces; and (b)a buffer layer for growth of epitaxial PbSe onto (111)-Si substrates. The MIS capacitors revealed breakdown strengths up to 4 MV cm ^-1 at 77 K and capacitance-voltage curves followed theoretical predictions from accumulation to inversion. Estimated interface state densities were ∼10 ¹²cm^-2V^-1 and carrier lifetimes were in the picosecond range. In preliminary experiments, Schottky diodes were fabricated on the top PbSe layer of PbSe/BaF ₂/Si stacks. These diodes revealed resistance-area products up to 0.14Ωcm ² at quantum efficiencies of ≃ 40%, corresponding to detectivities of up to D∗ (λ) _p ≃ 1.5 · 10 ¹⁰cmHz {1}/{2} W ^-1 at the peak wavelengths λ _p ≃ 7 μm at77 K.