Showing papers on "Schottky barrier published in 1971"

Studies of tunnel MOS diodes, I. Interface effects in silicon Schottky diodes

Abstract: A theoretical and experimental study has been made of silicon Schottky diodes in which the metal and semiconductor are separated by a thin interfacial film. A generalized approach is taken towards the interface states which considers their communication with both the metal and the semiconductor. Diodes were fabricated with interfacial films ranging from 8 to 26 A in thickness, and their characteristics are related to this model. The effects of reduced transmission coefficients together with fixed charge in the film are investigated. The interpretation of the current-voltage characteristics and the validity of the C−2-V method in the determination of diffusion potentials are discussed.

Studies of tunnel MOS diodes II. Thermal equilibrium considerations

Abstract: The oxide thickness δ of a tunnel MOS diode is varied over the range 10 to 45 A. This is done in an effort to establish the restrictions upon δ for which thermal equilibrium in the semiconductor is a valid approximation under the application of bias. Particular attention is paid to the reverse-bias case, and most of the experimental results are for δ>25 A. A transition is observed from the behaviour of the ideal Schottky barrier to that of the thick-film MOS device. The ac conductance and capacitance together with dc current characteristics are studied as continuous functions of bias. From these results, information is obtained which relates the quasi-Fermi levels for (i) majority carriers, (ii) minority carriers and (iii) electrons in the interface states to δ. Thermal equilibrium statistics are found to be applicable to the semiconductor in the presence of a bias voltage when δgreater, similar30 A, which compares with a theoretical prediction of δgreater, similar13 A.

Schottky-Barrier Anomalies and Interface States

Abstract: The surface‐state energy distribution at the metal‐semiconductor interface of a Schottky barrier has been deduced by combining a general theoretical analysis with one observed fact concerning the anomalous temperature dependence of the forward current on voltage. The fact, empirically found by Saxena, Padovani, and Sumner and by Padovani, is that the exponential terms of the forward‐current characteristic involve the sum of T plus T0. Here T is the absolute temperature and T0 is the empirical parameter which is essentially independent of temperature at constant current. This fact leads to the following new theoretical conclusions: (i) The surface‐state energy distribution near the Fermi level is a simple exponential with a characteristic e‐fold energy increase E0 that can be computed from T0. (ii) A plot of T0−1 vs voltage V yields essentially a straight line whose slope and intercept can be used to compute E0 and the barrier height φB. (iii) In reverse bias, φB varies as the log of the surface electric f...

Schottky barriers on p-type silicon

Abstract: Measurements have been made of the electrical characteristics of Schottky barriers made by evaporating films of various metals (Al, Pb, Ni, Au, Ag, Cu) onto p-type silicon. The barriers were generally lower than on n-type silicon, and in the case of Au the barrier was so low as to provide an effectively ohmic contact at room temperature. The truly exponential portion of the forward I–V characteristic was restricted to a comparatively small voltage range. Within this range ‘n’ values of about 1.10 were obtained. The reverse characteristics could be explained in terms of generation in the depletion region. The variation of barrier height with metal work-function indicates that the surface-state parameters (density of states and position of neutral level) are essentially the same for p-type as for n-type silicon. This is confirmed by the fact that, for a given metal, the sum of the barrier heights on n-type and p-type silicon is approximately equal to the band-gap.

Flicker noise in metal semiconductor Schottky barrier diodes due to multistep tunneling processes

Abstract: In a practical metal semiconductor Schottky barrier diode there is a certain amount of current flow by indirect tunneling through the barrier. Although this component of current is negligibly small compared to the thermionic emission or thermionic field emission current, a large low-frequency 1/f noise is associated with this multistep tunneling process. The multistep tunneling current introduces a random fluctuation of charge density at the trap states, which trap current carriers during the indirect tunneling process, in the space-charge region of the diode. The field intensity at the metal semiconductor interface is therefore modulated, which in turn modulates the Schottky effect and produces a random fluctuation of the diode current. The spectral intensity of noise due to this mechanism is calculated. Large flicker noise is expected at low frequencies.

Capacitance‐Voltage Characteristics of Metal Barriers on p PbTe and p InAs: Effects of the Inversion Layer

Abstract: The dependence of the capacitance C on the voltage is derived for metal‐semiconductor barriers in which there is a strong inversion layer at the metal‐semiconductor interface, a case of interest in the study of surface effects and in applications for laser structures Experimental results for evaporated lead and tin barriers on p PbTe at 77 °K and for evaporated gold barriers on p InAs at 77 and 42 °K are presented and compared to calculations performed with the inversion layer model Both the theory and experiment show an essentially linear dependence of C−2 with voltage, as in the usual Schottky barrier, but a voltage intercept which is surprisingly dependent on band‐structure parameters, bulk carrier concentration, and temperature Reasonable quantitative agreement between the theory and experiment is obtained In all cases the presence of a strong inversion layer can be clearly established The analysis of the capacitance‐voltage data, however, gives only a lower limit to the amount of inversion present

Noise behavior of Schottky barrier gate field-effect transistors at microwave frequencies

Abstract: The noise behavior of a Schottky barrier gate field-effect transistor is investigated by the use of the noise equivalent circuit. The influence of the carrier velocity saturation is estimated. The noise parameters are calculated by taking into account the influence of parasitic resistances. Measured and calculated noise parameters show good agreement in the frequency range 2-8 GHz.

Microwave mixer and detector diodes

Abstract: Recent advances in microwave mixer and detector diodes are reviewed. Devices considered are germanium back diodes, silicon and gallium arsenide point-contact diodes, and Schottky-barrier diodes. Current work on low-barrier (n-type) Schottky diodes and high-burnout point-contact diodes is also described. Experimental results of CW and RF pulse burnout of these devices are summarized. Different approaches to improve the power-handling capability of Schottky diodes at S-, X-, and K u -band frequencies are considered.

Formation of NiSi and current transport across the NiSi-Si interface

Abstract: The metallic compound NiSi has been produced by solid-solid metallurgical reaction in both n- and p-type silicon by sputtering Ni onto freshly back-sputtered silicon wafers and sintering for 5 min at 550°C. Identification of the orthorhombic (B31) monosilicide phase was made by X-ray diffraction, utilizing a glancing-angle Debye-Scherrer photograph of the 1300 A thin-film phase on the silicon substrate. NiSi Schottky barrier diodes, formed by this technique through holes in a silica mask and containing diffused guard rings around the periphery of the metallization, yield nearly ideal reverse I–V characteristics. The data have been fitted to a thermionic emission model for current transport, with barrier heights of 0.66 and 0.45 (eV) to n- and p-type silicon, respectively. The nature of the current transport characteristics strongly indicates the presence of a dipolar charge layer at the metal-semiconductor interface caused by quantum mechanical penetration of metallic electrons into the forbidden gap of the semiconductor.

An instrument for the rapid determination of semiconductor impurity profiles

Abstract: The instrument gives an absolute measurement of impurity concentration in a semiconductor wafer as a function of depth and surface position. A matrix of Schottky barrier diodes is deposited on the surface, contact being made with each diode in turn by a small probe. The probe is fed with a dc bias voltage and a small voltage at 100 kHz, the 100 kHz current flowing in the diode being a measure of the small-signal capacitance Cx. Another small voltage, at 1 kHz, is superimposed. and the consequent depth of modulation of the 100 kHz current is a measure of dCx/dV. The impurity concentration N and the depth are known functions of Cx and dCx/dV, and the instrument does the appropriate analogue computations to provide a direct plot of lg N against depth as the dc reverse-bias voltage is carried. This paper includes a detailed discussion of the sources of error, and also presents some typical impurity profile curves which have been obtained.

Schottky contact devices and method of manufacture

Abstract: A method is described for making plural semiconductor devices containing a Schottky contact by providing on one side of a semiconductor wafer a metal layer to form the Schottky contact, and then subjecting the opposite side of the wafer to an etching treatment which attacks the semiconductor but not the Schottky metal until semiconductor portions are etched away leaving spaced semiconductor islands whose contact surface with the Schottky method is surrounded by free surface portions of the metal. Then the metal layer is severed along lines spaced from the islands to leave in the final device, an exposed metal surround to increase the breakdown voltage.

Noise measure of metal-semiconductor--metal Schottky-barrier microwave diodes

Abstract: We calculate the impedance and noise measure of metal--semiconductor--metal (m.s.m.) microwave diodes. Assuming that the noise is caused by space-charge-smoothed shot noise accompanying the d.c. bias current, one comes to the conclusion that noise measures less than unity are possible. If shot noise is the main contributing noise source, then m.s.m. diodes should become extremely low-noise microwave oscillators and amplifiers.

Green Injection Luminescence from Forward-Biased Au-GaP Schottky Barriers

Abstract: Improvements in the minority‐carrier injection efficiency of GaP Schottky diodes are achieved by the incorporation, into the device, of a thin insulating layer separating the metal and the semiconductor. This enables visible green luminescence to be obtained from the diodes in forward bias. Measurements of the optical and electrical characteristics of this device are reported.

Solid state temperature sensor employing a pair of dissimilar schottky-barrier diodes

Abstract: The invention provides a solid state temperature sensor having significantly better sensitivity than conventional thermocouples. Basically, the sensor includes a pair of serially connected Schottky-barrier diodes of unequal barrier height and having geometries adapted such that each diode conducts the same reverse current at a given reverse bias and temperature. Because Schottky-barrier diodes of unequal barrier height have unequal thermal coefficients of reverse-biased resistance, the voltage at the common node between the diodes varies with temperature. Such voltage variation is useful for driving heating and/or cooling apparatus to stabilize the temperature of a semiconductor device and, additionally, for driving temperature indicators as in conventional thermometry.

Semiconductor device embodying field effect transistors and schottky barrier diodes

Abstract: A semiconductor device having at least one FET and at least one Schottky barrier diode. The device has an FET with source and drain regions in a semiconductor body and a gate electrode. The Schottky barrier diode consists of a thin layer of polycrystalline material separated from the semiconductor body by an insulating amorphous layer, an ohmic contact, and a barrier contact. The combination is particularly useful in fabricating logic and memory devices where the Schottky barrier diode is utilized as a resistance element and/or as an input output device. In the method of producing the device, a polysilicon layer is used to fabricate both the gate electrode and the Schottky barrier diode.

Hafnium‐Silicon Schottky Barriers: Large Barrier Height on p‐Type Silicon and Ohmic Behavior on n‐Type Silicon

Abstract: Schottky‐barrier diodes of Hf on p‐type Si gave a height φMS = 0.90 eV, which is the largest value of φMS reported to date on Schottky barriers on either p‐ or n‐type Si. Excellent agreement was found between the φMS values determined from current‐voltage, activation energy, and capacitance‐voltage analyses. This large value of φMS of the Hf‐(p)‐Si Schottky barrier allows several new applications which were not possible before in the integrated circuit technology, such as clamping of p‐n‐p transistors and fabrication of enhancement‐mode p‐channel Schottky gate field‐effect transistors. Hafnium deposited on n‐type Si (ND≅5×1015 cm−3) gave Ohmic behavior suggesting the validity of the work‐function‐difference model for the Hf–Si system. Under this assumption, the Schottky‐barrier analysis gives the work function of Hf=4.23±0.02 eV.

Schottky-gate bulk effect digital devices

Abstract: Using the n-GaAs planar device with a Schottky barrier gate, a high-field dipole domain could be triggered from the high-field region under the Schottky gate by applying a negative pulse to the gate. The figure of trigger capability was obtained to be 24 mA/V for the sample used in experiments, and is possible to get up to 150 mA/V for a suitably designed device. Some fundamental experiments including a pulse regenerator were performed.

Photovoltaic and electron-voltaic properties of diffused and Schottky barrier GaAs diodes☆

Abstract: The photovoltaic and electron-voltaic properties of GaAs diodes have been investigated for an irradiance in the range of 10−3 to 104 μW/cm2. These diodes were Zn diffused mesa-type diodes and Schottky barrier diodes having barriers of Au, Cu, and Cu/SiO. At 100 μW/cm2 diffused diodes can have a photovoltaic power conversion efficiency as high as 18 per cent for an absorption edge excitation at 8500 A and an open circuit voltage of 0·7 V. To achieve high efficiencies at short wavelengths, controlled etching of the front window can yield 11 per cent at 7000 A. For shorter wavelengths yet, Schottky barrier diodes are used to give efficiencies of 7 per cent at their peak spectral response of 6500 A and an open circuit voltage of 0·4 V. The quantum efficiency for these diodes is about 50 per cent for the photovoltaic mode of operation. The power conversion efficiency in the electron-voltaic mode is about 20 per cent of that in the photovoltaic mode, because greater energy is required to produce an electron-hole pair with an electron source than with an infrared radiation source. The energy required to produce an electron-hole pair in GaAs is 6·8 eV as deduced from the electron-voltaic quantum efficiency vs. electron energy curve.

Doping dependence of the barrier height of palladium-silicide Schottky-diodes

Abstract: Capacitance-voltage and current-voltage measurements have been used to determine the barrier height of palladium-silicon Schottky diodes. All diodes were heat-treated to form palladium silicide and the doping range of the silicon was varied in the range 5 × 1015 cm−3 to 2 × 1018 cm−3. The zero-electric-field (flat-band) barrier height was found to be independent of doping concentration in the above range, having a value 0·75 ± 0·01 eV. On the other hand the zero-bias barrier height is more electric-field dependent than the predictions of the usual image-force theory. However, the results are well described by an additional barrier lowering term of the approximate form Δφ = −χmϵm where ϵm is the maximum junction electric-field and χm a characteristic length in the region of 20–40 A.

Planar mesa Schottky barrier diode

Abstract: Planar silicon technology has been used to fabricate mesa Schottky barrier diodesh with high breakdown voltages. This method proves to be superior to alternate methods used to increase the breakdown voltage of Schottky diodes. The processing techniques and characteristics of mesa Schottky diodes are described in this paper.

High power microwave field effect transistor

Abstract: The present invention relates to field transistors having source and drain electrodes in ohmic contact with a semiconductor body, and having an intervening gate electrode of the Schottky barrier type. The present device is designed for high power and high frequency applications. These capabilities are achieved by use of a meandering channel of appreciable width, to which an efficient path for power transmission is provided at both low and high frequencies. The path entails the use of an additional conductive layer superimposed over the source and drain metallizations and not only providing a low resistance d.c. path to the gate, but also forming an efficient low phase dispersion transmission line into the active region of the device.

Avalanche ionization rates measured in silicon and germanium at low electric fields

Abstract: Ionization rates in semiconductors can be measured at low values of electric field using a new method involving a field-effect transistor (FET) structure which offers greater sensitivity than reverse biased p-n junction diode methods. Carriers of only one polarity cause ionization in the FET and no correction is required for ionization caused by carriers of the opposite polarity. Since secondary carriers resulting from ionization are attracted to a different terminal (gate or substrate) than that used to collect the primary carriers (drain), very small ionization currents can be detected. Values of electron ionization rate α n and hole ionization rate α p as low as 10-3cm-1have been obtained for silicon. The approximate relationship \alpha = \alpha_{\infin}e^{-b/E} is observed and the values of α at high fields correspond to those obtained conventionally. Values of α p from 0.04-1to 0.4 cm-1have been obtained for germanium. Analytical determination of electric field was provided by a solution of Poisson's equation for the field-effect structure. Difficulty in accurately determining the FET channel doping introduces a ± 30 percent uncertainty in electric field values. The method is applicable to any semiconductor material where junction, MOS, or Schottky barrier techniques can be used to construct field-effect transistors.

Schottky barrier phototransistor

Abstract: Disclosed is a metal-semiconductor-metal phototransistor formed by a pair of closely spaced, thin metal films in rectifying contact with the surface of a lightly doped p-type indium arsenide substrate. The spacing between the metal films is substantially less than the diffusion length of a minority carrier in the indium arsenide at the operating temperature, which is on the order of -78 DEG C. One metal film may be considered the collector region, the semiconductor material the base region, and the other metal film the emitter region. When the transistor is biased like an NPN transistor, the collector current is varied in proportion to the radiation striking the base region generally in the same manner as a photodiode, but the current modulation is many times that produced by a photodiode for a given radiation level.

Quantitative Aspects of the Tunneling Resistance in n‐GaAs Schottky Barriers

Abstract: The influence of the doping level and the barrier height on the characteristics of the differential resistance of M/n‐GaAs tunnel contacts has been investigated both theoretically and experimentally. The computation has been based on a pure WKBJ approximation and the quadrature over the momentum parallel to the interface was included. The position of the resistance maximum appears strongly dependent on the barrier height and insensitive to the value of the doping level. Vacuum‐cleaved contacts have been made with various metals, i.e., barrier heights, for two different values of the carrier density. In spite of some systematic absolute discrepancies, the experimental variations of the differential resistance with the barrier parameters are in good agreement with theory.

Semiconductor memory element

Abstract: A semiconductor memory element for use in a memory device having high speed data read out A semiconductor region of one conductivity type is provided on a substrate of an opposite conductivity A first electrode is in ohmic contact with the semiconductor region and a second electrode is coupled to the semiconductor region through a rectifying barrier such as a Schottky barrier or a PN Junction

Method for making a schottky-barrier field effect transistor

Abstract: A Schottky-barrier field effect transistor is disclosed with a semiconductor channel of relatively low conductivity between the source and drain electrodes which may be electrically influenced by a Schottky-barrier gate electrode located on the semiconductor channel. The transistor is characterized by a zone or region of higher conductivity which extends from the vicinity of the source electrode to near the gate electrode. Further, source and drain regions are conveniently provided for the transistor of semiconductor of the same conductivity type as the channel semiconductor at the Schottky-barrier electrode. Advantageously, the drain region may be made of semiconductor of high conductivity and the same conductivity type as the source region. The high conductivity region may be achieved through either diffusion or epitaxial growth technique.

Analysis of Photoemissive Schottky Barrier Photodetectors

Abstract: The performance of Schottky barrier photodetectors employing internal photoemission process is studied. Background‐photon‐noise limited detectivities Dλ* have been calculated for typical operating conditions. The use of cooled optical filters has also been investigated. The analysis shows that the detectivities may be considerably less (by about an order of magnitude) than those realized for the more conventional quantum detectors employing photovoltaic or photoconductive effects.

Electrical characteristics of GaAsP Schottky barrier diodes

Abstract: Schottky barrier diodes of chromium on n-type epitaxial gallium arsenide phosphide (GaAsP) were studied from 25°C to 440°C The diodes showed significant rectification properties up to a temperature of 440°C At high temperature the reverse leakage current was 115 mA at 25 V with a diode area of 114×10−3cm2 as compared with 025-μA current at room temperature The n factor derived from the slope of the ln I vs V curves was 11 The barrier height for chromium was found to be 125 eV from the capacitance measurements and 112 eV from the saturation current vs temperature measurements The slope of the C-V curves yielded a carrier concentration of 60×1015 carriers per cm3