The potential barrier between the metal and the semiconductor can be identified on an energy band diagram. In an ohmic interface, the total current density j entering the interface is a function of the difference in. On average, the electrons in the metal will tipically have lower energy than in the semiconductor lower e f. The present analysis is of great importance for the design of schottky barrier mosfet where doping density is. Modeling of dualmetal schottky contacts based silicon micro and nano wire solar cells m. These models are introduced as boundary conditions for the numerical solution of the semiconductor transport equations. Most semiconductor devices have either a sandwich structure or a planar structure, as illustrated in fig. The specific contact resistivity as calculated by eq.
In this model the electron transport analysis can be. B kt kt qjs 5 tunneling ohmic contacts an ohmic contact is defined as one. 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. Electrical and thermal simulators for silicon carbide power electronics akin akturk, zeynep dilli, neil goldsman. Mesh generator assigns mesh elements to volumeface groups. The catswhisker detectors used in the early days of wireless and metal rectifiers used in early power. Schottky barrier carbon nanotube transistors jing guo, supriyo datta and mark lundstrom.
The generally known, so called combined thermionic emissiondiffusion theory25 has successfully been used in many simu. A numerical study of scaling issues for schottky barrier. Schottky contact n doped electrons from conduction band or in the metal. What does one have to do for a metalsemiconductor junction to become an ohmic contact. In this way, we can consistently describe both ballistic and diffusive transport, with schottky or. Schottky diode definition, symbol, working and applications.
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 contact with interfacial layer a unbiased and b. Analytical model of the metalsemiconductor contact for device simulation. The reverse bias branch can be well fitted with the transverse effective mass mt 0. Properties of pt schottky type contacts on highresistivity cdznte detectors. Carrier transfer at each point along the metalcnt side contact is treated assuming an energyindependent transfer rate. This benchmark simulates the behavior of an ideal schottky barrier diode made of a tungsten contact deposited on a silicon wafer. Calculation of the electric field in gaas particle detectors. 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. Understanding contact gating in schottky barrier transistors from 2d channels. Schottky barrier height dependence on the metal work.
The contact resistance of each contact in a sandwich structure contact is given by. Schottky contact with the wire, and the other makes an ohmic contact. 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. Schottky barrier height determination by capacitance. Formulated for easy inclusion in numerical device simulators, current density boundary conditions for the heterodimensional contact are theoretically derived for both electrons and holes. Unlike conventional metalsemiconductormetal msm photodetectors, in which. For a schottky contact the current governed by thermionic emission over the barrier is given by js a t2 exp. The way to achieve such a contact is by doping the semiconductor heavily enough that tunneling is possible. Consider the case where, and the two materials come in contact. Influence of schottky diode modelling under flatband. Patterning metal contacts on monolayer mos2 with vanishing. Boundary conditions for the limiting cases of schottky and ohmic. The contact potential, the carrier contact concentration and, and in the case of a hd simulation, the contact carrier temperatures and are fixed.
Neutrality and equilibrium are as sumed for ohmic contacts and thermionic emission for rectifying schottky contacts. In such a device, the carrier dynamics is governed by boundary conditions which, therefore. The schottky barrier, shown in figure 62, is formed by an electron blocking contact for which. Modeling of dualmetal schottky contacts based silicon micro. Picture a shows the n type shottky contact under equilibrium conditions. 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.
Defect observations of nialgangan schottky contacts on. 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. Schottky barrier height dependence on the metal work function. C1 is a constant of integration and is determined with the boundary condition. 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. 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. Pdf a revised boundary condition for the numerical. Simulation of schottky and ohmic contacts on cdt e.
Stability of schottky and ohmic au nanocatalysts to zno. 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. An analytical model of nonideal ohmic and schottky contacts. The condition for a contact to be blocking, seen by electrons from the metal, is. We have investigated semiclassical carrier transport at the heterodimensional contact between a threedimensional 3dmetal and twodimensional 2dsemiconductor system. The detailed process conditions can be found in ref.
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. The schottky diode named after the german physicist walter h. Using the boundary condition at the cathode and at the edge of the depleted layer, one can find the width of the depleted layer. Typical schottky contacts consist of metallization stacks of a refractory contact metal and conductive overlayer. 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. At the schottky contact mixed boundary conditions apply. Thus there will be a transfer of electrons from the semiconductor into the metal holes are ignored. Schottky, also known as schottky barrier diode or hotcarrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. Analytical model of the metalsemiconductor contact for. In other words, a euclidean polyhedral surface is a surface equipped with, first, an intrinsic metric that is flat except at isolated points where it has conelike singularities, and. Modeling of current density boundary conditions for a heterodimensional contact of 3dmetal to 2dsemiconductor article in journal of computational electronics 31. Using the boundary condition at the cathode and at the edge of the depleted layer, one can find the.
Schottkytoohmic crossover in carbon nanotube transistor contacts v. Leakage current analysis of diamond schottky barrier diode. Properties of pt schottky type contacts on highresistivity. A euclidean polyhedral surface is a surface obtained from gluing euclidean polygons along their edges. Neumann boundary conditions, interfaces be tween semiconductor and dielectrica, ideal ohmic contacts, schottky. Now putting the boundary condition ix l 0, and finding. Previous works on schottky barrier diode considered only uniformly doped doping density. The cv characteristics were measured using agilent 4284a precision lcr meter at 1mhz. 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. 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. 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. Electrical and thermal simulators for silicon carbide power electronics. Theoretical and experimental investigations of nano. A revised boundary condition for the numerical analysis of schottky barrier diodes.
The calculation of depletion width of a nonuniformly doped schottky barrier diode is rarely treated in the literature. How are schottky diodes modeled for circuit design. Pdf simulation of schottky and ohmic contacts on cdte. A critical study of boundary conditions in device simulation. 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. Schottky contact between the gold layer and the underlying wire segment. Electrical and thermal simulators for silicon carbide. Schottky barrier height determination by capacitancevoltage. It has a low forward voltage drop and a very fast switching action. 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. Pdf a revised boundary condition for the numerical analysis of. In the following we will briefly discuss the boundary conditions used in the simulation. The 1 term is added to account for the current flowing from right to left. Depletion width of a nonuniformly doped schottky barrier diode.
Schottkytoohmic crossover in carbon nanotube transistor. Influence of schottky diode modelling under flatband conditions on the simulation of submillimeterwave mixers jose v. Theoretical and experimental investigations of nanoschottky. The semiconductor contact potential is the difference between the metal quasifermi level and the metal work function.
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. Properties of pt schottky type contacts on highresistivity cdznte detectors aleksey e. 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 barriers can also be used to characterize a semiconductor. Contact resistance and specific contact resistivity. Understanding contact gating in schottky barrier transistors. A surface is a connected twodimensional manifold, possibly with boundary. Particle simulation and asymptotic analysis of kinetic equations for modeling a schottky diode by p. Sensitivity of the mott schottky analysis in organic solar cells. An analytical model of nonideal ohmic and schottky. Boundary conditions for device simulation are derived by. Pdf a new boundary condition for the computer simulation of schottky barrier diodes is proposed.
Thus there will be a transfer of electrons from the semiconductor into the metal holes are. Usually the boundary conditions have been formulated exclusively for open circuit. 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. Modeling of dualmetal schottky contacts based silicon. One of the essential contact problems is the mod elling of sehottky contacts.
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. Voltagecontrolled ohmic contact dirichlet boundary. The model covers the entire range from schottky to ohmic contacts and fits. In a normal pn junction diode, a ptype semiconductor and an ntype semiconductor are used to form the pn junction.
Highly rectifying silicon schottky contacts using energetically deposited graphitic carbon a thesis submitted in fulfilment of the requirements for the degree of. Sensitivity of the mott schottky analysis in organic solar. An alsi schottky contact formed in our device processing conditions, will have an ex. Metalsemiconductor ohmic contacts stanford university. Conduction mechanisms for metalsemiconductor contacts. Particle simulation and asymptotic analysis of kinetic. Solution of the above equations with appropriate boundary conditions will give the. Pdf a revised boundary condition for the numerical analysis. A planar alsi schottky barrier mosfet operated at cryogenic. Note, however, that there are recent reports that cntfets.