PLASMONS LOCALIZED AT POINT CHARGES IN SEMICONDUCTOR QUANTUM-WELLS

The plasmon excitations of inhomogeneous carrier gases in semiconducto r quantum wells in the presence of point charge impurities are investi gated. The random phase approximation for the carrier gas yields an in tegral equation which expresses the condition that plasmons may be sel f-consistently localized in the vicinity of the impurity. The localize d plasmon is a density wave trapped at the impurity site and exists in the electron (hole) gas only for negative (positive) impurity charge. Bound states of the intersubband plasmon are found for all densities of the carrier gas in a quantum well, a result which differs qualitati vely from the bulk case. Numerical results for the binding energies ar e given for a range of relevant parameters.