Effect of screening on the optical absorption of a two-dimensional electron gas in GaAs-AlxGa1-xAs heterostructures
The optical-absorption spectrum is calculated for a quasi-two-dimensional electron gas interacting with polar optical phonons in a GaAs-AlxGa1-xAs heterostructure. The importance of dynamical screening, the effect of the finite width of the two-dimensional electron layer, and the temperature dependence are investigated. The polaron mass is derived and is found to decrease with increasing electron density. For electron densities around 1012 cm-2 the absorption spectrum shows in addition to the usual structure a shoulder at energy EF+ħωLO with EF the Fermi energy and ħωLO the optical-phonon energy.