Schottky Barrier Electrical Properties

We refer the reader to Ref [122] for general information on the occurrence of a potential barrier at the metal/semiconductor interface, that is, the Schottky barrier problem, as it exceeds the scope of this review. 

We consider the contact formed by TM silicides with silicon. The silicide layer is grown by solid state reaction of die TM and Si at high temperature. Outward diffusion removes contaminants from the interface in most cases, so that the silicide/silicon contact layer is clean and well defined, a critical aspect to obtain a reliable Schottky barrier height tkg. Metallurgical defects are the most common limitations of these junctions, as they are induced by the solid state reaction. The 

Several phenomena affect the properties of the Schottky barrier. The first relevant feature to be controlled is the stoichiometry of the semiconductor surface region upon contact formation. Various methods have been developed to control the stoichiometry, including depositing a very thin layer between the metal and the semiconductor. 

Silicides epitaxially grown on silicon possess additional attractive advantages such as a higher thermal and chemical stability and a well-ordered interface of high quality. Moreover, it is possible to re-epitaxy silicon on top of these epitaxial 

FeSij 0.67 [12] a phase is metallic, p phase is a p-type semiconductor 

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Schottky Diode Growth. The electrical properties of the films deposited using SSP 1 (Fig. 6.13) were evaluated by current versus voltage (I-V) measurements recorded for the thin films using thermally evaporated aluminum contacts (10mm2), to make Schottky barrier diodes (see Fig. 6.14). 

The rectification properties of semiconductor interfaces are the most important electrical characteristic of semiconductor contacts. Certain types of devices, such as transistors, require both ohmic and rectifying contacts on a given semiconductor surface, whereas other devices, such as Schottky barriers, are based on the inherent rectification properties of semiconductor/metal Junctions. Numerous photonic devices, such as photon detectors and photovoltaic cells, require rectification at a semiconductor Junction, and light-emitting diodes require both ohmic contacts and rectifying Junctions in a well-defined geometry. Thus, successful fabrication of a desired device structure depends entirely on the electrical properties of the specific semiconductor contacts that are formed in the process. The principles described above allow the rational fabrication of contacts with the desired properties, and also describe the operation of the resulting devices within a simple, chemically intuitive, kinetic framework. 

The concept of using heteropolyacids in the chemical bath was developed during the 1990s for deposition of CdSe, Sb2S3, CdS, CdTe, etc. The effect of heteropolyacids on the physical, optical, and electrical properties of the films was determined. Their performance in photoelectrochemical, Schottky barrier, and heteroj unchon solar cells has been investigated. 

Nalwa HS (ed) (1996) Handbook of organic conductive molecules and polymers, vol 2 and 3. WUey, New York, NY Nalwa HS (ed) (1997) Handbook of organic conductive molecules and polymers, vol 4. Wiley, New York, NY Nguyen VC, Potje-Kamloth K (1999) Electrical and chemical sensing properties of doped polypyrrole/gold Schottky barrier diodes. Thin Solid Films 338 142-148... 

D.R. Lillington An Investigation of the electrical and optical properties of silicon Schottky barrier photovoltaic cells PhD thesis (1978). 

We have carried out an investigation of the electrical and electro-optical properties of a series of Schottky barrier diodes fabricated with polyacetylene sandwiched between two metal contact layers, one to form the Schottky barrier and the other (gold) to provide an ohmic contact [56]. This type of structure is straightforward to fabricate with an extrinsically-doped semiconductor and there have been several reports of such devices which use polyacetylene or other conjugated polymers [57-62]. The details of the device fabrication have been given in section 3.2, and we show in figure 10 the details of the typical structures that we have used for this work. We have worked with relatively thick films of polyacetylene, in the range 500 - 1(XX) nm, so as to avoid the possibility of short-circuits tetween top and bottom electrode, but we have kept the metal contact layers thin so that they are semi-transparent and allow optical transmission measurements. 

Another important result is the dependence of the band-gap of semiconducting carbon nanotubes on the tube diameter. The band-gap of a semiconducting nanotube is inversely proportional to its diameter [22]. Because carbon nanotubes of different geometries exhibit different electrical characteristics, the connection of a metallic nanotube with a semiconducting nanotube will result in a Schottky barrier device, and the connection of two different semiconducting tubes will result in a heterojunction structure [30]. These structures have been shown to exhibit asymmetric electtical properties, both in carbon nanotubes and in traditional CMOS circuits [31], The usefulness of these structures in present-day circuits underscores how useful carbon nanotubes may be in the development of next-generation electrical devices [32,33]. 

It is difficult to measure metal/polymer Schottky energy barriers smaller than about 0.5 eV using internal pholoemission. Small Schotiky energy barriers lead to thermal emission currents produced by the absorption of light in the metal which are difficult to separate from true photocurrents 134]. If the structure is cooled to try to improve this contrast, it is often found that the significant decrease in the electrical transport properties of the polymer [27 [ makes it difficult to measure the internal photoemission current. To overcome this limitation, internal photoemission and built-in potential measurements are combined to measure small Schottky energy barriers, as described below. 

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