INTERSUBBAND RAMAN-SCATTERING IN INAS ALSB QUANTUM-WELLS/

Raman spectroscopy has been used to study intersubband transitions in InAs/AlSb single quantum wells grown by molecular-beam epitaxy on (100 ) GaAs substrates using strain-relaxed AlSb or GaSb buffer layers. Fro m the measured energies of the coupled longitudinal optical phonon-int ersubband plasmon modes the single particle transition energies betwee n the first and second confined electron subbands were deduced as a fu nction of the width of the pseudomorphically strained InAs well. Subba nd spacings calculated including the effects elf strain and nonparabol icity were found to be in agreement with the experimental transition e nergies. For a given well width, the two-dimensional electron concentr ation deduced from the Raman measurements was found to be lower than t he concentration measured in the dark by Hall effect, but showed a sig nificant increase with increasing optical excitation intensity.