Raman spectroscopic determination of electron concentration in n-type GaInAsSb

Phonon-plasmon coupled mode Raman spectra of n-type GaInAsSb were measured at room temperature as a function of electron concentration. A relatively simple spectral model for the electronic contribution to the dielectric function was evaluated to determine the electron concentration from the bulk coupled mode spectra. The electron concentration was determined from a Raman spectrum by minimizing the sum of the squared residuals between a measured and a simulated spectrum. The only two fitting parameters were the Fermi energy and a plasmon damping parameter. The electron concentrations determined from the fits to the Raman spectra were compared to the electron concentrations determined from single magnetic field Hall effect measurements that were corrected to account for carriers in two conduction band minima. Compared to the results obtained from the Hall effect measurements, the electron concentrations obtained using Raman spectroscopy were as much as approximate to 19% lower at low doping levels but not more than approximate to 1% higher at higher doping levels. At lower carrier concentrations, the deviations are attributed to limitations of the spectral model. At higher carrier concentrations, the two methods were in good agreement. However, given the known limitations of this relatively simple spectral model, this agreement may be fortuitous; i.e., elements of the spectral model that tend to increase the apparent carrier concentration may be offset by elements that decrease the apparent carrier concentration.