Growth and characterization of C60/GaAs interfaces and C60 doped GaAs

Abstract

Intensity oscillations of reflection high-energy electron diffraction are observed during epitaxial growth of a C60 layer on GaAs substrates. The frequencies of the oscillations coincide well with the growth rates of C60 layers, suggesting that C60 layers grow by layer-by-layer growth mode. Anomalous oscillations are observed in the initial stage of C60 layer growth on a GaAs (111)B surface with (2×2) structure. These oscillations indicate that the growth of the first C60 layer is completed at the point of approximately 0.5 monolayer coverage. This phenomenon is explained by a model in which C60 adsorption sites are limited by As trimers adsorbed on the GaAs (111)B surface. C60 uniformly doped and δ-doped GaAs and AlGaAs layers are grown by migration enhanced epitaxy method. Crystalline and electrical characteristics of the layers are investigated by transmission electron microscopy (TEM) and electrochemical capacitance voltage (ECV) measurements. The layers are confirmed to have no defect and well-defined δ-doped structures by TEM measurement, and ECV profiles of C60 δ-doped GaAs and AlGaAs layers suggest that C60 molecules in GaAs and AlGaAs lattice produce deep traps, which can be charged or discharged by applied electrical fields.