The lattice sites of carbon in highly doped AlAs:C grown by molecular beam epitaxy.

Infrared absorption measurements of heavily carbon-doped AlAs have revealed a localized vibrational mode at 630 cmhigh-1 which appears as a Fano profile. Raman scattering measurements show a corresponding line at 634 cmhigh-1: possible reasons for the difference in frequency are discussed. The line is assigned to CsubAs acceptors and a comparison is made with a two-parameter Keating cluster model. Additional weaker lines at 615 cmhigh-1, 633 cmhigh-1 and 645 cmhigh-1 have been observed in absorption, and possible interpretations have been considered.