Study of the impurity photoconductivity in p-InSb using epitaxial p + contacts

The optical absorption coefficient alpha in p (+)-InSb layers (with hole concentrations of p a parts per thousand 1 x 10(17)-1.2 x 10(19) cm(-3)), grown by liquid-phase epitaxy on p-InSb substrates, is measured in the spectral range of 5-12 A mu m at 90 K, and the impurity photoconductivity is measured (at 60 and 90 K) in p (+)-p structures. It is found that a in the p (+) layers reaches a value of 7000 cm(-1) (at p a parts per thousand 2 x 10(19) cm(-1)). It is shown that the measured substrate value of (alpha a parts per thousand 1-3 cm(-1)) is overestimated in comparison with estimates (alpha a parts per thousand 0.1 cm(-1)) based on comparing the photoconductivity data. This discrepancy is explained by the fact that the optical transitions of holes responsible for photoconductivity are obscured by the excitation of electrons to the conduction band. The photoionization cross section for these transitions does not exceed 1 x 10(-15) cm(2).