Effect of electron-hole recombination processes on semiconductor reflectivity modulation

Abstract

The increases in the reflectivity of germanium, silicon, GaAs, GaSb, InAs, InSb, CdTe, and CdSe have been observed by use of a ruby laser to produce the electron-hole plasma that is responsible for the reflectivity changes and to probe the reflectivity changes. Observations were made with the ruby laser light incident at the pseudo-Brewster angle in order to measure small increases in reflectivity. In the case of the III-V and II-VI semiconductors, the increase in reflectivity was found to exhibit a linear dependence when plotted as a function of the square root of the incident light intensity. Germanium and silicon exhibited a linear dependence of the increase in reflectivity on the incident light intensity. These results agree with the calculated dependence that ascribes the differences between the two groups of semiconductors to the fact that the recombination of electrons and holes is a direct process in the III-V and II-VI compounds and in germanium and silicon occurs mainly by trapping of the free carriers at impurity centers. (Author)