Photovoltaic infrared sensors in heteroepitaxial PbTe on Si

Arrays of photovoltaic infrared sensors for thermal imaging applications have been fabricated in narrow gap PbTe grown heteroepitaxially on Si substrates. PbTe epitaxy was achieved with the aid of intermediate CaF2 /BaF2 buffer layers of only ≊2000 Å thickness. Blocking Pb contacts on about 3-μm-thick p-PbTe layers form the active areas of the sensors. Cutoff wavelengths are 5.6 μm, and resistance-area products are up to R0A=400 Ω cm2 at 85 K with mean value R0A≊150 Ω cm2 for 66 element linear arrays, well above the room-temperature photon field background noise limit. The temperature dependence of R0A indicates a depletion-limited noise current behavior between 250 and 100 K.