Spectral sensitivity dependencies of backside illuminated planar MCT photodiodes

Spectral sensitivity dependencies of Hg1−xCdxTe (0.20 ⩽ x ⩽ 0.25) backside illuminated planar photodiodes were investigated at T = 80 K to study their longwavelength edge features. It was shown that the longwavelength part of these spectral dependencies is mainly formed by the exponential wavelength dependence of the optical transitions. Empirical dependencies of cut-off wavelengths at different values (λmax, λ0.5, λ0.9) were obtained. The influence of the epitaxial layer thickness on the maximum sensitivity position was also studied.