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

Abstract

This paper is the continuation of the analysis of a method of determining the cutoff wavelength λ _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 λ _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 µm, respectively, in λ _c if λ _c=10 µm. Measurements on photodiodes fabricated on the basis of Cd_0.24Hg_0.76Te (λ _c=8.1 µm) epitaxial layers showed that the difference in the values of λ _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.