Observations of free-electron plasmons in heavily doped $n$-type germanium by light scattering are presented. They are made possible by the choice of the laser frequency near the $E_1$ gap of Ge (∼2.22 eV). The effect is confirmed by the polarization selection rules and the dependence on uniaxial stress. The latter reveals band-tailing effects. Application to the characterization of laser-annealed ion-implanted samples is discussed.

• Received 28 November 1983

DOI:https://doi.org/10.1103/PhysRevB.29.3737