Abstract

In GaAs, longitudinal-optical (LO) phonons are known to form coupled modes with the collective charge-density oscillations of a bulk electron plasma that are admixtures of electron and lattice oscillations.¹ A similar coupling also occurs between LO phonons and the collective intersubband charge-density oscillations of quasi-two-dimensional (2D) electron systems that exist in modulationdoping GaAs-AlGaAs single heterostructures and quantum wells.² In this paper we report resonant-Raman-scattering measurements demonstrating that in a GaAs δ-doped doping superlattice, coupled electron-phonon excitations have a different nature, i.e., a bulk LO one-phonon state dressed by a continuum of electron intersubband transitions.³

© 1993 Optical Society of America