Use of two low-temperature emitters to determine the cutoff wavelength of the photosensitivity of infrared photodetectors

This paper is the continuation of the analysis of a method of determining the cutoff wavelength lambda(c) of infrared photodetectors by irradiating the sample with radiation from two blackbodies with different temperatures. The emitters can operate at lower temperatures as the cutoff wavelength lambda(c) is increased. The parameters of a system employing two blackbodies, which are placed inside a liquid-nitrogen cryostat and have temperatures of 260 and 320 K, respectively, are presented. It is shown that an error of 1 K in determining the lower or higher temperature produces an error of approximately 0.3 and 0.2 mu m, respectively, in lambda(c if) lambda(c) = 10 mu m. Measurements on photodiodes fabricated on the basis of Cd0.24Hg0.76Te lambda(c) = 10 8.1 mu m. epitaxial layers showed that the difference in the values of lambda(c) obtained by this method and from spectral measurements is no more than several tenths of a micron. It is suggested that this method be used as a standard method. (C) 1998 American Institute of Physics. [S1063-7826(98)02409-0].