Chapter 6 Photovoltaic Infrared Detectors

Publisher Summary This chapter reviews the status of Hg 1– x Cd x Te photovoltaic infrared detector technology. For 3–5 μm applications at operating temperatures around 190K and for 8–12μm applications at around 77 K, ion implanted n -on- p Hg 1– x Cd x Te junction photodiodes have already demonstrated sufficiently high R o A products. For these combinations of cutoff wavelength and operating temperature, p -side diffusion current generally dominates the current–voltage (I-V) characteristics near V=0. Efforts are being directed toward the further reduction of p -side diffusion current by reducing the p -side diffusion volume and by using p -type Hg 1– x Cd x Te with long minority-carrier lifetime. For applications at lower temperatures where conventional diffusion current is negligible, various leakage current mechanisms have generally kept junction impedances below their desired values so far. This is particularly so for junctions with longer cutoff wavelengths and is presumably because of the ease with which interband tunneling can occur across the narrow bandgaps involved. Efforts are being directed toward identifying the origins of leakage currents with particular emphasis on the control of surface potential and surface state density and on device designs, which are less conducive to interband tunneling.