Room-temperature Raman spectroscopy was used to characterize n-type-doped In0.53Ga0.47As and In0.52Al0.48As layers by observing coupled longitudinal-optical (LO) -phonon-plasmon mode spectra as a function of carrier density. Carrier densities determined from the high-frequency L+ coupled mode shift in the Raman spectra were compared to carrier densities determined from electrochemical capacitance-voltage profiling measurements. In In0.53Ga0.47As with carrier densities n≤8×1017 cm-3 accurate determination of carrier densities from the Raman spectra was hindered by Landau damping and small L+ mode dispersion. Better agreement between the two techniques was observed in In0.53Ga0.47As and In0.52Al0.48As for carrier densities of about 8×1017 cm-3 and higher, doping levels at which Landau damping is less pronounced. Surface band bending was evaluated from changes in Raman intensity as a function of carrier density of dipole-allowed LO-phonon modes originating in the surface space-charge region. Values for the surface built-in potential determined from the Raman spectra were found to be smaller than those obtained from electrical measurements. The discrepancy is attributed to screening of the surface dipole by photogenerated carriers.
ASJC Scopus subject areas
- Condensed Matter Physics