Raman spectroscopic determination of hole concentration in p-type GaSb

Abstract

Phonon-plasmon coupled mode Raman spectra of p-type GaSb were measured at room temperature as a function of hole concentration. These spectra were obtained using an optical system based on 752.55nm excitation in order to obtain more sensitivity to bulk GaSb coupled mode Raman scattering than is possible with visible wavelength excitation-based systems. A relatively simple spectral model for the electronic contribution to the dielectric function was evaluated for determination of hole concentration from the bulk coupled mode spectra. The hole concentration was determined from the Raman spectra by minimizing the sum of the squared residuals between a measured and simulated spectrum as a function of total hole concentration and a plasmon damping parameter. The hole concentrations determined from the fit to the Raman spectra were compared to the hole concentrations determined from single magnetic field Hall effect measurements that were corrected to account for two band conduction. The hole concentrations determined using the two methods differed by ≈3% to ≈33% for single magnetic field Hall effect hole concentrations from ≈5.51×1017to≈6.38×1018cm−3. The agreement between the hole concentrations determined using the two methods was worse for single magnetic field Hall effect hole concentrations below ≈5.51×1017cm−3. In general, compared to the hole concentrations determined from Hall effect measurements corrected to account for two band conduction, the hole concentrations determined from the Raman spectra were higher for epilayers with the lower Hall effect hole concentrations and lower for the epilayer with the highest Hall effect hole concentration. The deviations between the two methods were attributed to the limitations of the spectral model employed and uncertainties in GaSb materials properties.