Aluminum modified silicon surfaces: Optical and electrical characterization

Abstract A set of silicon substrates was treated depositing aluminum on its polished surface and then sintered for a long time up to 8 h. After aluminum removal, the formation of rectangular pits like inverted pyramids was observed. The analysis made by Rutherford backscattering spectroscopy reveals that during the sintering process aluminum and oxygen diffuses inside silicon and the amount of the first one inside silicon is practically proportional to the sintering time, but oxygen achieves its maximum concentration for the sample sintered during four hours. According to the electrical characterization made by fitting the current–potential and the impedance electrochemical curves, oxygen is a key factor in the diminution of the Schottky barrier height, which in the framework of the impedance analysis, is interpreted as a lowering of the surface resistance for charge transfer. According to the X-ray diffraction, this fact is associated with the surface lattice modification which yields surface strain due to oxygen presence, whereas aluminum was identified as an important factor in reducing the silicon complex refractive index insofar aluminum increases.