Photomodulation Raman scattering spectroscopy of n-doped GaAs surfaces

Photomodulation Raman spectroscopy (PM-RS) has been employed to determine the total surface charge density and the surface minority carrierʹs lifetime in n-type GaAs, using the forbidden LO phonon scattering. In PM-RS, the photomodulating-pumping beam is incident on the sample while the Raman measurements are in progress. The photogenerated carriers partly neutralize the surface charges. Two different doping concentration of (011) GaAs surface were used. The total surface charge density has been obtained as a function of the photomodulating intensity considering a constant depletion electric field for the lower doping case. The minority carrierʹs lifetime was also determined through dynamical measurements for the PM-RS as ≈21 s, in a good agreement with other measurements.