Study of photoexcited plasma in p-doped GaAs beveled structures by micro-Raman spectroscopy

The generation and properties of photoexcited steady-state plasma of electrons and holes in bevel-shaped p-type GaAs structures were studied by micro-Raman spectroscopy. The best correspondence of theoretical calculations with experimental spectra was obtained by using of photoexcited carrier concentration of 1.1 x 1017 cm-3 and mobility 600 and 40 cm2/V s for the photoexcited steady-state electrons and holes, respectively. The analysis of the plasma behavior and its coupling with longitudinal optical phonons at different positions along the bevel shows that the mode resulting from this coupling causes the changes of Raman intensities recorded in frequency positions of transversal (TO) and longitudinal (LO) optical phonon peaks. These changes were further studied and physical interpretation was provided. The dependence of their ratio in the region affected by surface depletion layer can be fitted by linear function very well. The linearity was observed at all studied structures. This behavior on beveled structures prepared by special treatment with very low bevel angle can be used for analysis of the p-type GaAs nanostructures, particularly for measurement and extraction of a doping profile of p-type impurities in GaAs with very high resolution in nm scale