Infrared Absorption and Electron Effective Mass inn-Type Gallium Arsenide

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 $(0.078\mathrm{}\pm 0.004)m$ with an indication of an increase for the sample of highest carrier concentration. This value is substantially larger than previously reported values.