Raman spectroscopic assessment of Si and Be local vibrational modes in GaAs layers grown by molecular beam epitaxy.

We have performed a Raman study of heavily Si and Be doped GaAs grown by molecular beam epitaxy. Both impurities give rise to local vibrational modes which can be observed in Raman spectroscopy for impurity concentrations exceeding about 2x10 high 18 cm high minus 3. Compared to absorption spectroscopy, which is the "classical" technique to study LVM in relatively thick (equal or bigger than 1 mym) layers, Raman spectroscopy allows us to analyze the incorporation of both dopants in thin (equal or smaller than 10 nm) as-grown GaAs layers.