Infrared Absorption in Gallium Arsenide-Gallium Phosphide Alloys

Abstract

The infrared absorption has been quantitatively investigated with respect to the shape, the temperature dependence and the carrier concentration dependence of the additional absorption band in the region from 1000 to 4000 cm⁻¹. The experimental method for the determination of the threshold energy was discussed. The present experimental results have given a reasonably clear indication of the difference between the additional absorptions in n-GaAs-rich alloys and ones in n-GaP-rich alloys. Especially, the additional bands in n-GaAs-rich alloys were concluded to occur by a transition of conduction electron from the lowest band minimum to the upper subsidiary one. The dependence of the threshold energy on composition x was found to be expressed as Eₜ＝0.29-0.67x (eV). The empirical cross over point occurred at 43 mol% GaP. On the other hand, in n-GaP and GaP-rich alloys, the additional band showed a relatively sharp peak and all the absorption shapes were similar to the previous analysis. The threshold energy was found to depend to a small extent on the composition. The dependence could be illustrated in terms of the composition dependence of the ionization energy.