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The infrared absorption between 0. 85 and 25 microns has been measured as a function of carrier concentration for n-type single-crystal gallium arsenide. The absorption in the 1- to 5-micron region is compatible with a model in which there are minima 0. 25 ev above the bottom of the conduction band. Infrared reflectivity measurements on several samples of different carrier concentrations were used to deduce the free-carrier contribution to the electric susceptibility and the electron effective mass. The results indicate a value for the mass of (0. 0780. 004) m with an indication of an increase for the sample of highest carrier concentration. This value is substantially larger than previously reported values.
Spitzer et al. (Wed,) studied this question.