Photoluminescence and Raman characterization of heavily doped Al_0.3Ga_0.7As grown by solid-soruce molecular beam epitaxy using carbon tetrabromide

摘要

Carbon incroporation in Al_0.3Ga_0.7As is systematically studied in solid soruce molecular beam epitaxy as a function of carbon tetrabromide pressure and substrate temeprature. The maximum free carrier concentration attained was 1.5×10~20 cm~-3. No effect of substrate temeprature on doping density was observed for temepratures in the range 560-700 deg C. The carrbon-induced lattice contraction in AlGaAs determined by X-ray diffraction was found to be proportional to hole density and similar to the contraction in GaAs. Carbon-doped samples exhibited anomalously bright room temperature photoluminescence at wo excitation density. The increase in full-width at half-maximum of the 4 K photoluminescence peak and in the TO-to-LO GaAs-like mode intensity ratio in Raman spectroscopy shows a reduciton in material qualtiy for the samples grown in the "forbidden temeprature range" between 600 and 640 deg C.