No abstract

No abstract

Near intrinsic single crystals of normalPbSe grown from the vapor have been used to construct photoconductive detectors for operation at room temperature. Fabrication of the detectors depends on the use of a newly developed chemical etch to reduce the specimens to thicknesses of a few microns, and to provide surfaces with low carrier recombination velocity. The highest detectivity, D* , achieved was 3.7×108 cm cps½ watt−1 normalat 4.4μ ; Various methods of estimating bulk carrier lifetimes have been used; the value for the best crystal measured was in excess of 4 μsec. The surface recombination velocity of the best etched surface was below 80 cm sec−1. Similar etches can be used for normalPbS and normalPbTe .

Photoconductive layers of PbTe have been formed by evaporation on substrates at different temperatures. The size of crystals in the layers has been estimated from electron micrographs and x-ray diffraction, and a correspondence has been obtained between crystal size and the limit of spectral response. Sensitivity up to the long wave-length limit set by the energy gap is not achieved unless the crystals are greater than a critical size; for lead telluride this is about a quarter of a micron. A similar effect has been shown to occur with PbSe.Photoconductive layers of PbTe are commonly prepared by an evaporation technique usually in a low pressure of oxygen, followed by a sensitizing heat treatment either in vacuo or in a low pressure

No abstract