Rectification Behavior Evaluation of Si Cone Diodes in Dependence of Contact Metallization and Printable Nanoparticle Thin Film Modification

Recently, we were able to demonstrate Si cone Schottky diodes processed from printable nanoparticle dispersion which can operate at switching speeds well beyond 4 GHz [1], [2]. The challenge of these devices, however, is a relatively low rectification ratio in the order of 10 to 100. Therefore, in this contribution the rectification behavior of such diodes is evaluated in terms of effective Schottky barrier height (SBH), ideality factor and rectification ratio for different contact metals as well as Si cone height distributions. We find that the effective SBH is only weakly dependent on the metal work function of thermally evaporated metals due to strong Fermi-level pinning. In consequence, this parameter has limited influence on the rectification behavior of this diode type. However, in previous theoretical publications [3], [4], we demonstrated that the non-ideal rectification behavior of cone diodes can be explained by Gaussian distributed SBHs as the result of the variation in Si cone heights. In accord with this model, we investigate different cone height distributions generated from varying nanoparticle deposition profiles, which are formed by spin coating and by controlling the coffee ring-effect in inkjet printed droplets. With this variation in cone height distribution, we observe a linear relation between SBH and ideality factor, which indicates a Gaussian SBH distribution. Therefore, to improve the rectification ratio, the standard deviation of the cone height distribution needs to be reduced, which leads to a lower ideality factor and a greater effective SBH. This is facilitated by using small-area cone diode devices.