Observation of coupled LO phonon-intersubband plasmon modes in GaSb/InAs quantum wells by resonant Raman scattering

Abstract

Two new peaks are observed in resonant Raman scattering from GaSb/InAs quantum wells grown on (001) GaAs by MBE. These two lines are assigned to the coupled LO phonon-intersubband plasmon modes originating from the InAs wells. The lower-frequency branch of the coupled system (L- mode) lies between the LO and the TO frequencies of InAs, and the line intensity depends strongly on the two-dimensional carrier concentration and the laser excitation energies (resonant near the E1 gap of InAs). The L+ line is weak and relatively broad. Its frequency increases with increasing carrier concentration in the InAs wells and is not observed when the carrier concentration is low.