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

Intensity oscillations of reflection high-energy electron diffraction are observed during epitaxial growth of a C-60 layer on GaAs substrates. The frequencies of the oscillations coincide well with the growth rates of C-60 layers, suggesting that C-60 layers grow by layer-by-layer growth mode. Anomalous oscillations are observed in the initial stage of C-60 layer growth on a GaAs (1 1 1)B surface with (2 x 2) structure. These oscillations indicate that the growth of the first C-60 layer is completed at the point of approximately 0.5 monolayer coverage. This phenomenon is explained by a model in which C-60 adsorption sites are limited by As trimers adsorbed on the GaAs (1 1 1)B surface. C-60 uniformly doped and delta-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 delta-doped structures by TEM measurement, and ECV profiles of C-60 delta-doped GaAs and AlGaAs layers suggest that C-60 molecules in GaAs and AlGaAs lattice produce deep traps, which can be charged or discharged by applied electrical fields. (C) 2010 Elsevier B.V. All rights reserved.