Analytical model of the metalsemiconductor contact for. The schottky barrier, shown in figure 62, is formed by an electron blocking contact for which. Neumann boundary conditions, interfaces be tween semiconductor and dielectrica, ideal ohmic contacts, schottky. In such a device, the carrier dynamics is governed by boundary conditions which, therefore. The constants a, b and c are found from the boundary conditions, nx 0 0 at the left contact and n x l 0 at the right contact, and are given by 2 21 1 x xx ml l e ac ee cg. Properties of pt schottky type contacts on highresistivity. The specific contact resistivity as calculated by eq. Boundary conditions for device simulation are derived by.
The calculation of depletion width of a nonuniformly doped schottky barrier diode is rarely treated in the literature. Several approaches have been proposed to address these problems8, including trying different metallic alloys and doping9,10, using a metallic phase of mos 2 11 or a hexagonal boron nitrayer as interface between the metal contact and the semiconducting mos 2. Schenk et al analytical model of the metalsemiconductor contact for device simulation tween ohmic and schottky, and the data are not influenced by an unknown bulk resistance. Contact currents are given in a fully analytical form and agree well with those from the reference model over the whole range of doping concentrations from schottky to ohmic. It has a low forward voltage drop and a very fast switching action. Schottky contact with the wire, and the other makes an ohmic contact. Schottky contact between the gold layer and the underlying wire segment. Pdf a revised boundary condition for the numerical analysis of. In an ohmic interface, the total current density j entering the interface is a function of the difference in the equilibrium fermi levels on the two sides. This benchmark simulates the behavior of an ideal schottky barrier diode made of a tungsten contact deposited on a silicon wafer. Solution of the above equations with appropriate boundary conditions will give the.
Leakage current analysis of diamond schottky barrier diode hitoshi umezawa,a takeyasu saito, norio tokuda, masahiko ogura, sunggi ri, hiromichi yoshikawa, and shinichi shikata diamond research center, national institute of advanced industrial science and technology aist, tsukuba center 2, tsukuba, ibaraki 3058568, japan. Analytical model of the metalsemiconductor contact for device simulation. One of the essential contact problems is the mod elling of sehottky contacts. Theoretical and experimental investigations of nanoschottky. Solar cells of this type have a long history, dating back to 1883, when charles fritts coated selenium with a thin layer of gold to. Schottky contact with interfacial layer a unbiased and b. Understanding contact gating in schottky barrier transistors.
Schottkytoohmic crossover in carbon nanotube transistor. Schottky barrier height dependence on the metal work function. Theoretical and experimental investigations of nano. The band bending is caused by the difference in work functions of the two materials.
The schottky contact is put at x 0 while an ohmic contact is assumed at x l. The contact resistance of each contact in a sandwich structure contact is given by. Leakage current analysis of diamond schottky barrier diode. C1 is a constant of integration and is determined with the boundary condition. Modeling of current density boundary conditions for a. A revised boundary condition for the numerical analysis of schottky barrier diodes. Schottky barrier carbon nanotube transistors jing guo, supriyo datta and mark lundstrom. In a normal pn junction diode, a ptype semiconductor and an ntype semiconductor are used to form the pn junction. The potential barrier between the metal and the semiconductor can be identified on an energy band diagram. The catswhisker detectors used in the early days of wireless and metal rectifiers used in early power. The polysilicon contact boundary conditions for the carrier temperatures and and the lattice temperature are similar to the ones which apply for the ohmic contact, i. Schottky, also known as schottky barrier diode or hotcarrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal.
A numerical study of scaling issues for schottky barrier. Contact resistance and specific contact resistivity. Depletion width of a nonuniformly doped schottky barrier diode. The reverse bias branch can be well fitted with the transverse effective mass mt 0. Picture a shows the n type shottky contact under equilibrium conditions. Influence of schottky diode modelling under flatband conditions on the simulation of submillimeterwave mixers jose v.
In an ohmic interface, the total current density j entering the interface is a function of the difference in. Conduction mechanisms for metalsemiconductor contacts. How are schottky diodes modeled for circuit design. Pdf a new boundary condition for the computer simulation of schottky barrier diodes is proposed. Properties of pt schottky type contacts on highresistivity cdznte detectors.
Pdf simulation of schottky and ohmic contacts on cdte. Schottkytoohmic crossover in carbon nanotube transistor contacts v. Properties of pt schottky type contacts on highresistivity cdznte detectors aleksey e. Electrical and thermal simulators for silicon carbide power electronics. Now putting the boundary condition ix l 0, and finding the solution for vx, we can find the contact resistance as the ratio of the input voltage and input current as. Usually the boundary conditions have been formulated exclusively for open circuit. For a schottky contact the current governed by thermionic emission over the barrier is given by js a t2 exp. For detectors such as schottky detectors for which longwavelength responsivity is desired, or for detectors requiring maximization of responsivity, a transparent contact can be used. The usual schottky contact model is derived from a given barrier height and a thermionic emission current across the schottky barrier, while the conventional model for ohmic contacts simply states charge. Schottky diode definition, symbol, working and applications. Schottky junction solar cells a photovoltaic cell can be created from the schottky junction between a semiconductor and a metal, with or without an insulating layer between them.
Schottky contact n doped electrons from conduction band or in the metal. Sensitivity of the mott schottky analysis in organic solar cells. Voltagecontrolled ohmic contact dirichlet boundary. Using the boundary condition at the cathode and at the edge of the depleted layer, one can find the. The condition for a contact to be blocking, seen by electrons from the metal, is.
On average, the electrons in the metal will tipically have lower energy than in the semiconductor lower e f. Highly rectifying silicon schottky contacts using energetically deposited graphitic carbon a thesis submitted in fulfilment of the requirements for the degree of. The schottky diode named after the german physicist walter h. The present analysis is of great importance for the design of schottky barrier mosfet where doping density is. In this model the electron transport analysis can be. Sensitivity of the mott schottky analysis in organic solar. Pdf a revised boundary condition for the numerical.
The model covers the entire range from schottky to ohmic contacts and fits. Tunneling ohmic contacts an ohmic contact is defined as one in which there is an unimpeded transfer of majority carriers from one material to another, i. Schottky diode is a metalsemiconductor junction diode that has less forward voltage drop than the pn junction diode and can be used in highspeed switching applications. Electrical and thermal simulators for silicon carbide power electronics akin akturk, zeynep dilli, neil goldsman.
Particle simulation and asymptotic analysis of kinetic equations for modeling a schottky diode by p. A planar alsi schottky barrier mosfet operated at cryogenic. An alsi schottky contact formed in our device processing conditions, will have an ex. Boundary conditions for the limiting cases of schottky and ohmic. The 1 term is added to account for the current flowing from right to left. Modeling of dualmetal schottky contacts based silicon micro and nano wire solar cells m. The detailed process conditions can be found in ref.
The cv characteristics were measured using agilent 4284a precision lcr meter at 1mhz. A pn junction diode is one of the simplest semiconductor devices around, and which has the characteristic of passing current in only one direction only. Using the boundary condition at the cathode and at the edge of the depleted layer, one can find the width of the depleted layer. What does one have to do for a metalsemiconductor junction to become an ohmic contact. Consider the case where, and the two materials come in contact. Mesh generator assigns mesh elements to volumeface groups. Thus there will be a transfer of electrons from the semiconductor into the metal holes are ignored. The semiconductor contact potential is the difference between the metal quasifermi level and the metal work function. Stability of schottky and ohmic au nanocatalysts to zno. These models are introduced as boundary conditions for the numerical solution of the semiconductor transport equations. Simulation of schottky and ohmic contacts on cdt e.
Schottky barrier height determination by capacitancevoltage. An analytical model of nonideal ohmic and schottky. In this way, we can consistently describe both ballistic and diffusive transport, with schottky or. Schottky barrier height determination by capacitance. Neutrality and equilibrium are as sumed for ohmic contacts and thermionic emission for rectifying schottky contacts. Formulated for easy inclusion in numerical device simulators, current density boundary conditions for the heterodimensional contact are theoretically derived for both electrons and holes. Previous works on schottky barrier diode considered only uniformly doped doping density. Influence of schottky diode modelling under flatband. A schottky barrier carbon nanotube fet uses the nonideal contact between a metal and a carbon nanotube to form a schottky barrier that can be used to make extremely small schottky diodes, transistors, and similar electronic devices with unique mechanical and electronic properties. We have investigated semiclassical carrier transport at the heterodimensional contact between a threedimensional 3dmetal and twodimensional 2dsemiconductor system.
The way to achieve such a contact is by doping the semiconductor heavily enough that tunneling is possible. Novel devices require novel design rules 4 1 abstract the closetoideal properties of novel silicon carbide schottky diodes coolsic, that can reach higher blocking voltages than the actual silicon schottky limit of 250 v, are well suited for hard switching commutation. B kt kt qjs 5 tunneling ohmic contacts an ohmic contact is defined as one. In the following we will briefly discuss the boundary conditions used in the simulation. Defect observations of nialgangan schottky contacts on. The contact potential, the carrier contact concentration and, and in the case of a hd simulation, the contact carrier temperatures and are fixed. Electrical and thermal simulators for silicon carbide. Schottky barrier height dependence on the metal work. Note, however, that there are recent reports that cntfets.
Particle simulation and asymptotic analysis of kinetic. Modeling of dualmetal schottky contacts based silicon. Pdf a revised boundary condition for the numerical analysis. Modeling of dualmetal schottky contacts based silicon micro. Thus there will be a transfer of electrons from the semiconductor into the metal holes are. Calculation of the electric field in gaas particle detectors. A surface is a connected twodimensional manifold, possibly with boundary. Understanding contact gating in schottky barrier transistors from 2d channels.
At the schottky contact mixed boundary conditions apply. Modeling of current density boundary conditions for a heterodimensional contact of 3dmetal to 2dsemiconductor article in journal of computational electronics 31. The generally known, so called combined thermionic emissiondiffusion theory25 has successfully been used in many simu. An analytical model of nonideal ohmic and schottky contacts. Electrical and thermal simulators for silicon carbide power. Now putting the boundary condition ix l 0, and finding. Most semiconductor devices have either a sandwich structure or a planar structure, as illustrated in fig. A critical study of boundary conditions in device simulation. Theoretical and experimental investigations of nanoschottky contacts mohd rezeq,1,2,a khouloud eledlebi,1 mohammed ismail,1 ripon kumar dey,2 and bo cui2 1department of electrical and computer engineering, and ksrc, khalifa university of science technology and research, pob 127788 abu dhabi, united arab emirates 2department of electrical and computer engineering, university of waterloo. Carrier transfer at each point along the metalcnt side contact is treated assuming an energyindependent transfer rate. The behaviour of the pn junction with regards to the potential barriers width produces an asymmetrical conducting two terminal device, better known as the pn junction diode. Leakage current analysis of diamond schottky barrier diode hitoshi umezawa,a takeyasu saito, norio tokuda, masahiko ogura, sunggi ri, hiromichi yoshikawa, and shinichi shikata diamond research center, national institute of advanced industrial science and technology aist. Theoretical and experimental investigations of nanoschottky contacts mohd rezeq,1,2,a khouloud eledlebi,1 mohammed ismail,1 ripon kumar dey,2 and bo cui2 1department of electrical and computer engineering, and ksrc, khalifa university of science technology. Metalsemiconductor ohmic contacts stanford university.
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