Junction Schottky

Four different types of junctions can be used to separate the charge carriers in solar cebs (/) a homojunction joins semiconductor materials of the same substance, eg, the homojunction of a p—n sibcon solar ceb separates two oppositely doped layers of sibcon 2) a heterojunction is formed between two dissimbar semiconductor substances, eg, copper sulfide, Cu S, and cadmium sulfide, CdS, in Cu S—CdS solar cebs (J) a Schottky junction is formed when a metal and semiconductor material are joined and (4) in a metal—insulator—semiconductor junction (MIS), a thin insulator layer, generaby less than 0.003-p.m thick, is sandwiched between a metal and semiconductor material. 

Cartiers can also be generated in a semiconductor by the absorption of light or injected into the semiconductor from ap—n or Schottky junction. In either case, as soon as the source is removed the density of those excess carriers begins to decrease exponentially with time. The time it takes for the density to be reduced to 1/ of the original value is defined as the carrier lifetime, T. For siUcon, T is typically in the microsecond range. 

Fi.g 1 a—e. Charge transfer processes at pn-junctions (left side) and semiconductor-metal Schottky junctions (right side). 

The authors ascribed the high activity of Au/thoria to a Schottky junction effect between the metal and oxide leading to an enhancement of active OH groups associated with oxygen deficiencies. The authors did observe formation of formate, carbonate, and bicarbonate species, but are still elucidating which, if any, of the species are important for the mechanism. 

Most electrochemical experiments need an electrical contact of some kind to the silicon substrate. Because of the semiconducting nature of silicon a metallic tip or clip attached to the surface will not produce an ohmic contact but constitutes a Schottky junction. However, for some applications, like the ELYMAT (Section 10.3), where the contact is only operated under forward conditions at low current densities, such a contact is sufficient. For silicon samples with a doping concentration in excess of 1019 cnT3 the contact to a metal becomes ohmic. An ohmic contact to a silicon sample with a doping concentration below 1019 cm-3 can be achieved in different ways ... 

The charge states of the silicon electrode in alkaline electrolytes have not been investigated in detail. It can be assumed that the electrode represents an MIS structure above PP, while it behaves similarly to a Schottky junction for potentials below PP. 

The nanocarbon-Ti02 Schottky junction plays a crucial role in the photovoltaic characteristics of a semiconductor electrode [89]. According to the thermionic emis-... 

This cell employs a solid state photovoltaic to generate electricity that is then passed to a commercial-type water electrolyzer (see Chapter 2). An alternative system involves the semiconductor photovoltaic cell configured as a monolithic structure and immersed directly in the aqueous solution, see Chapter 8 this cell involves a solid-state p-n or schottky junction to produce the required internal electric field for efficient charge separation and the production of a photovoltage sufficient to decompose water [49-51]. 

The doped poly(acetylene) forms various junctions such as a) a p-n junction from p- and n- -f CH, b) a hetero-Schottky junction from the inorganic semiconductor and metalic -f CH-, and c) a heterojunction from the inorganic semiconductor and semiconducting The bandgaps of -(-CH (trans- 0.6 eV, cis- 0.9 eV)... 

The simplest electronic devices, such as diodes, light-emitting diodes, lasers, and photocells, have a single p-n junction. If we place, say, a p-type doped Si block in contact with n-typed doped Si block, electrons will normally flow from the n to the p regions but not vice versa. Thus, the p-n diode so created can be fitted with ohmic contacts to function as a rectifier of alternating current. Schottky junctions can act in this way to some degree even without deliberate creation of a p-n junction. 

Schottky junction - [SILICON AND SILICON ALLOYS - PURE SILICON] (Vol 21) -m solar cells [PHOTOVOLTAIC CELLS] (Vol 18)... 

If neither of these goals can be realized, layered semiconductors may not become useful electrode material in either semiconductor liquid junction or Schottky junction devices. Fortunately, evidence is already being obtained that the negative effects due to steps can be at least temporarily and partially alleviated (35, 36). Future development of chemical methods to inhibit deflection of minority carriers to the edges of steps and to reduce the high recombination rates at steps may open the way for the use of polycrystalline layered chalcogenide semiconductors in solar cell devices. 

Fig. 9.21 Change of the dead-layer thickness Dd = Di -D2 upon exposure of Pd to hydrogen in the photoluminescent Schottky junction...

Fig. 7 Flatband situation for RuS2 in different electrolytes as measured by Ktxhne and Tributsch (1985), interpreted by us as due to a RuS2/Ru02-Schottky junction pinned to the electrolyte redox potential...

Field emission is characterized by its temperature independence. Here meff is the effective mass of the carrier in the dielectric. The essential assumption of the Schottky model is that a carrier can gain sufficient thermal energy to cross the barrier that results from superposition of the external field and image charge potential. Neither tunnelling nor inelastic carrier scattering is taken into account. The following current characteristic is predicted for the Schottky junction ... 

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