Abstract
A quantum mechanical theory of the infrared absorption by conduction electrons in InSb is developed according to the second-order perturbation formula in degenerate cases. The absorption coefficient due to acoustical phonons is calculated by means of the deformation-potential method. The deformation-potential constant E1 is only contained as an unknown parameter and the values of the other quantities are obtainable from measurements. The magnitude of E1 can be easily determined from the comparison between the theory and experiments, and thus an information about the scattering mechanism is obtainable.
When |E1| is taken as 30 eV, the present theory is in excellent agreement with the experiment of Kessler and Sutter for various carrier concentrations and wave lengths and also with that of Spitzer and Fan for a more wide range of wavelength. It is also shown that the theoretical value of the optical cross section for free electrons in pure materials is quite consistent with the value found by Kurnick and Powell. With the E1 value obtained, the contribution of acoustical phonons to the absorption is estimated to be most important in all cases of experimental data.
A discussion on the screened Coulomb potential used in the calculation of the impurity scattering is given.
