INCORPORATION OF CARBON IN HEAVILY DOPED ALXGA1-XAS GROWN BY METALORGANIC MOLECULAR-BEAM EPITAXY

Hole concentrations in excess of 1020 cm-3 have been achieved in AlxGa1-xAs using carbon doping during metalorganic molecular beam epitaxy. Hall and secondary-ion mass spectrometry measurements show a 1:1 correspondence between the hole density and carbon concentration in as-grown samples, although post-growth annealing at 900°C leads to a reduction in the net free-carrier concentration (typically a decrease of ∼40% for 30 s anneals). The carbon-localized vibrational modes (LVMs) show fine structure due to the presence of three different symmetries for substitutional carbon CAs, namely Td, C2 v, and C3v. The experimental CAs LVM line positions are in remarkable agreement with the predictions of a rigid ion model.