Formation of vertical graphene on surface of the gallium-arsenide structures

The properties of carbon layers (C-layers) formed by thermal decomposition of CCl$_4$ at temperatures of 600–700$^\circ$C on the surface of gallium arsenide structures fabricated by MOC-hydride epitaxy on $n^+$-GaAs (100) wafers have been studied. The surface morphology of the carbon layers was studied using atomic force microscopy. The structural and optical properties were studied using Raman spectroscopy and reflection spectroscopy. It has been found that in the case of a C-layer fabricated at a temperature of 650–700$^\circ$C, the atomic force microscopy image demonstrates the presence of vertical carbon nanowalls (vertical graphene) located parallel to one of the [110] directions of the GaAs crystal lattice. The characteristics of the bands observed in the Raman spectra correspond to the parameters of the spectra of vertical graphene. The reflectivity coefficient of such carbon layers significantly decreases (diffuse reflection does not exceed 25% for a layer fabricated at 700$^\circ$C) in the wavelength range from 0.19 to 1.8 $\mu$m. The presence of a significant “absorbing” ability makes the obtained carbon layers promising as a conducting contact in photosensitive semiconductor device structures, which is confirmed by preliminary results of studies of the current-voltage characteristics and spectral dependences of the photocurrent.