Optimization of ohmic contacts to n-type GaAs nanowires

摘要

III-V nanowires are comprehensively studied because of their suitability foroptoelectronic quantum technology applications. However, their small dimensionsand the spatial separation of carriers from the wire surface render electricalcontacting difficult. Systematically studying ohmic contact formation bydiffusion to $n$-doped GaAs nanowires, we provide a set of optimal annealingparameters for Pd/Ge/Au ohmic contacts. We reproducibly achieve low specificcontact resistances of $\sim2\times10^{-7}\,\Omega\text{cm}^2$ at roomtemperature becoming an order of magnitude higher at $T\simeq4.2\,$K. Weprovide a phenomenological model to describe contact resistances as a functionof diffusion parameters. Implementing a transfer-matrix method, we numericallystudy the influence of the Schottky barrier on the contact resistance. Ourresults indicate that contact resistances can be predicted using variousbarrier shapes but further insights into structural properties would require afull microscopic understanding of the complex diffusion processes.