Investigation of nano patches in Ni/n-Si micro Schottky diodes with new aspect

Abstract

High-quality Ni/n-Si Schottky barrier diodes (SBDs) with low reverse leakage current were produced using a molybdenum (metal) mask. An identical preparation of the diodes shows a diode-to-diode variation in the ideality factor and barrier height parameters. Topological, phase and potential distribution investigations of the surface before and after preparation of the thin metal film for ohmic and Schottky contacts with a Conducting Probe Atomic Force Microscope (CP-AFM) show that thin metal film deposited on Ni/n-Si Schottky diode (SD) consists of many nano patches. Investigation of the patches in the ohmic contact side shows that these ohmic contacts also consist of nano patches in the range 20–40 nm with a variation in the potential distribution reaching about 1 V, resulting in different electrical behaviors in different regions of the contact surface. Even with sufficient care in the preparation and cleaning of the contact surface there is a potential difference of about 0.5 V between different parts of the semiconductor surface, which is one of the sources of different electrical behaviors of the substrate. These patches are sets of parallelly connected and electrically cooperating nano contacts with size between 20 and 40 nm. The barrier heights (BH) and ideality factor ( n) are affected by the potential distribution on the surface. There is a spot field between the patches with different local work functions, which are in direct electrical contact with the surrounding patches. It is shown that in the real metal–semiconductor (MS) contacts, patches with quite different configurations, various geometrical sizes and local work functions are randomly distributed on the metal surface. The relation between ideality factor ( n) and potential barrier height (BH) depends on the distribution of patches and their work functions.