Growth kinetics in position-controlled and catalyst-free InAs nanowire arrays on Si(111) grown by selective area molecular beam epitaxy

摘要

We investigated the interwire distance dependence on the growth kinetics of vertical, high-yield InAs nanowire arrays on Si(111) grown by catalyst-free selective area molecular beam epitaxy (MBE). Utilizing lithographically defined SiO_2 nanomasks on Si(111) with regular hole patterns, catalyst-free and site-selective growth of vertically (111)-oriented InAs nanowires was achieved with very high yields of ～90 percent. Interestingly, the yield of vertically ordered nanowires was independent of the interwire distance and the initial growth stages. Significant size variation in the nanowires was found to depend critically on the interwire distance and growth time. Two growth regimes were identified-(i) a competitive growth regime with shorter and thinner nanowires for narrow interwire distances and (ii) a diffusion-limited growth regime for wider distances, providing good estimates for the surface diffusion lengths. Surprisingly, despite these size-dependent effects the nanowire geometries remained unaltered with uniform, almost nontapered morphologies even over large variation in nanowire density (～mid-10~6-10~9 cm~(-2) range). X-ray diffraction further confirmed the vertical (111) directionality with low crystal tilt by rocking curve widths (to scans) as low as ～0.6°. These findings demonstrate the capability to precisely tailor the position and size of well-oriented III-V semiconductor nanowires through noncatalytic MBE selective area growth and provide an important step toward fully integrated, uniform vertical III-V nanowire array-on-Si devices.