Silicon Oblique Substrate Silicon Germanium Nanowires Growth And Characteristics Of The Study

Very small and compactly arranged GeSi nanowires were self-assembled on vicinal Si (001) substrates with～8°off toward (110) during Ge deposition. The nanowires were all oriented along the miscut direction. The small ration of height over width of the nanowire indicated that the nanowires were bordered partly with {105} facets. These self-assembled small nanowires were remarkably influenced by the growth conditions and the miscut angle of substrates in comparison with large dome-like islands obtained after sufficient Ge deposition. These results proposed that the formation of the nanowire was energetically driven under growth kinetic assistance.A multilayer of GeSi nanowires separated with Si spacers was readily self-assembled on miscut Si (001) substrates with8。 off toward<110>. The nanowires were very small and compactly arranged on the vicinal surface. Systematic photoluminescence (PL) spectroscopy studies were carried out on the GeSi nanowires were carried out. With increasing excitation power, a sublinear power dependent PL intensity and a blue-shift of～7meV/decade with nearly constant full width of half maximum (FWHM) of PL peaks from multilayer GeSi nanowires was observed. These results indicated a typical type-Ⅱ band alignment of GeSi nanowires/Si. The blue-shift was attributed to band bending effect with the increase of photon-generated carriers. The nearly independent FWHM of PL peaks with the excitation power was explained in terms of the formation of mini-band due to strong coupling of holes in closely neighboring nanowires. An activation energy of～12meV was extracted from the temperature-dependent intensity of PL peaks of the nanowires, which was assigned to be the exciton binding energy around the nanowires. Based on Raman spectra, the Ge content in GeSi nanowires was estimated to be～61%.