OPTICAL-SCATTERING AND ABSORPTION BY METAL NANOCLUSTERS IN GAAS

Optical extinction by a dilute dispersion of metal nanoclusters in GaAs is calculated using the optical theorem and Maxwell-Garnet theory with complex dielectric functions for Cr, Fe, Ni, Cu, Ag, Au, Er, and As. The large dielectric function of the semiconductor host shifts the surface plasmon resonance frequencies from the ultraviolet to the near infrared. The noble metals have well-defined resonances with significant absorption and Rayleigh scattering at photon energies compatible with diode lasers and semiconductor electro-optic modulators. Interband transitions in metals such as As, Cr, Fe, Ni, and Br strongly damp the surface plasmon modes, quenching the resonant absorption by the particles, but providing significant absorption to wavelengths longer than 1(,)5 mu m. Metal-semiconductor composites may arise during growth or processing of materials, such as GaAs:Er for fiber-optic applications, and GaAs:As in which metallic precipitates of As form in GaAs after low temperature growth of GaAs using molecular beam epitaxy.