Infrared absorption of silicon isotopes in gallium phosphide

Abstract

Infrared absorption measurements at ∼80°K on ²⁸Si‐ and (²⁸Si+³⁰Si)‐doped GaP grown by liquid‐phase epitaxy and compensated by electron irradiation are presented. Several new bands are observed with samples containing the mixed isotopes. The observed frequencies of ²⁸Si‐related bands agree with previously reported values, and the isotopic shifts for ³⁰Si‐related bands agree with values calculated from local mode theory. The results indicate that one band is attributable to a defect containing two Si atoms on nonequivalent sites, presumably nearest‐neighbor substitutional pairs. The present measurements confirm the previous observations of a much larger concentration of pairs than that predicted by random statistics.