Transition to insulating behavior in the metal-semiconductor digital composite ErAs : InGaAs

Superlattice structures of semimetallic ErAs particles embedded in an InGaA s matrix were fabricated on (001) Fe doped InP substrates with varying amou nts of ErAs. The samples were characterized by temperature dependent Hall m easurements, x-ray diffraction, and transmission electron microscopy. The t emperature dependence of the mobility, charge density, and sheet resistance is presented. The apparent offset between the conduction band minimum of t he InGaAs matrix and the Fermi energy of the ErAs particles is strongly dep endent on the amount of ErAs deposited. The offset is determined from the m easured charge density and the InGaAs density of states. As the size of the ErAs particles increases, the Fermi level decreases from similar to0.01 eV above the InGaAs conduction band edge to similar to0.15 eV below the InGaA s conduction band edge and the electrical conduction properties change from metallic to semiconducting. (C) 2001 American Vacuum Society.