IR-sensor array fabrication in Pb1−xSnxSe-on-Si heterostructures

Large line or area arrays of photovoltaic infrared sensors are desired for thermal imaging and spectroscopic applications. The sensor arrays should be arranged on Si-substrates because of size, costs and the possibility to integrate the read-out electronics of large arrays directly into the Si-substrate. We therefore grow narrow gap Pb1−xSnxSe layers by molecular beam epitaxy (MBE) on Si(111)-substrates. A CaF2 epitaxial buffer layer is used for compatibility reasons. Photovoltaic infrared sensor arrays for the 8–12 μm atmospheric window are fabricated in the 2–4 μm thick layers by photolithographic techniques with 8 mask levels and 6 simple wet etching steps. The operability of the sensor arrays is demonstrated by recording thermal images with a simple camera.