Raman study of low growth temperature GaAs

A Raman study has been made of GaAs grown by MBE at low temperature, which is known to produce nonstoichiometric (As‐rich) material. The epilayer has a slightly larger lattice constant than the GaAs substrate, as measured by x‐ray diffraction. Raman measurements show that the LO phonon of LT‐GaAs is shifted down in frequency from that of bulk GaAs. The shift is related to the presence of AsGa antisite defects, which cause a reduction in the electric field associated with the LO phonon. After the sample was annealed, the epilayer had the same lattice constant as the substrate, and the LO phonon moved closer to that of bulk GaAs.