G-Doping-Based Metal-Semiconductor Junction

Abstract

Geometry-induced doping (G-doping) has been realized in semiconductors nanograting layers. G-doping-based p-p(v) junction has been fabricated and demonstrated with extremely low forward voltage and reduced reverse current. The formation mechanism of p-p(v) junction has been proposed. To obtain G-doping, the surfaces of p-type and p+-type silicon substrates were patterned with nanograting indents of depth d = 30 nm. The Ti/Ag contacts were deposited on top of G-doped layers to form metal-semiconductor junctions. The two-probe method has been used to record the I–V characteristics and the four-probe method has been deployed to exclude the contribution of metal-semiconductor interface. The collected data show a considerably lower reverse current in p-type substrates with nanograting pattern. In the case of p+-type substrate, nanograting reduced the reverse current dramatically (by 1–2 orders of magnitude). However, the forward currents are not affected in both substrates. We explained these unusual I–V characteristics with G-doping theory and p-p(v) junction formation mechanism. The decrease of reverse current is explained by the drop of carrier generation rate which resulted from reduced density of quantum states within the G-doped region. Analysis of energy-band diagrams suggested that the magnitude of reverse current reduction depends on the relationship between G-doping depth and depletion width.

Large Area Patterning of Highly Reproducible and Sensitive SERS Sensors Based on 10-nm Annular Gap Arrays

“…Of particular interest is the creation of uniformly narrow gaps, with precise control of gap size on noble metal substrates, ideally using low-cost, high-yield, and time-saving techniques. Various nanofabrication methods, such as electron-beam/extreme-ultraviolet lithography (EBL/EUV) [ 13 , 14 , 15 ], focused-ion beam (FIB) milling [ 16 , 17 , 18 ], metal nanoparticles assembly [ 19 , 20 , 21 ], nanosphere lithography (NSL) [ 22 , 23 , 24 ], capillary force-assisted lithography [ 25 , 26 ], block copolymer lithography (BCL) [ 27 , 28 ], interference lithography [ 29 , 30 , 31 ], and DNA origami [ 32 , 33 , 34 , 35 ] have been developed and used to pattern highly hierarchical ordered metallic nanostructures with nanogap features for the purpose of making SERS substrates. Among these methods, for instance, EBL/EUV methods are still not stable and reproducible enough to create nanogaps down to 10 nm, which are well known for obtaining ultra-strong electromagnetic field enhancement [ 12 , 36 ], and, additionally, are cost-intensive and time-consuming for fabricating nanostructures over wide areas.…”