RESONANT RAMAN-SCATTERING AND PHOTOLUMINESCENCE AT THE E(0)-BAND GAP OF CARBON-DOPED ALAS

Carbon-doped AlAs grown by solid source molecular beam epitaxy has bee n studied by Raman and photoluminescence spectroscopy. Doping levels e xceeding 2 X 10(19) cm-3 have been obtained using a heated graphite fi lament as the carbon source. For excitation just above the AlAs E0 ban d-gap energy radiative recombination is observed across that band gap, which involves nonthermalized photogenerated electrons occupying the GAMMA-conduction-band minimum rather than the lowest indirect X minima . Raman spectra excited in resonance with the E0 band gap show a hole- plasmon-longitudinal-optical-phonon coupling similar to that found in p-type GaAs. Resonantly excited Raman spectra further reveal a vibrati onal mode at congruent-to 635 cm-1, which is assigned to the local vib rational mode of the C(As) acceptor in AlAs.