Intersubband Transitions in Piezoelectric Superlattices

Charge-density and spin-density intersubband transitions of electrons in \100\ and \111\ GaSb/AlSb multiple quantum wells have been measured with inelastic light scattering. These measurements indicate that large built-in electric fields exist in the \111\ oriented samples because of the piezoelectric effect. Furthermore, these built-in fields can be screened by the optical generation of an electron-hole plasma.