Showing papers on "Schottky diode published in 1969"

Normalized thermionic-field (T-F) emission in metal-semiconductor (Schottky) barriers

Abstract: Thermionic field (T-F) emission in uniformly doped metal-semiconductor (Schottky) barriers is analyzed to yield a normalized solution in closed form for the forward and reverse current (I)-voltage (V) relationship. A quasi one-dimensional approach and Maxwell-Boltzmann statistics are used. The formulation is expressed in terms of the ‘flat-band’ current density Im, the band bending Eb in the semiconductor depletion region, the materials constant E0 0 ( ln [ I I m ] = − E b E 0 0 at 0°K in the WKB approximation), and kT. The kinetic energy in units of Eb at which the maximum injection of carriers occurs in the semiconductor is shown to be cosh -2(kT/E0 0). Current flow in the temperature range between pure thermionic emission (kT/E0 0 ⪢ 1) and pure field emission (kT/E0 0 ⪡ 1) is analyzed and criteria for the transition of T-F emission to thermionic and to field emission are given. Computer solutions for the energy distribution of the injected carriers and for the normalized I-V characteristic are presented in graphical form. The results permit a straightforward calculation of the barrier height and the impurity concentration in the semiconductor from measurements of current density and differential resistance at a single applied bias. Application of these results explains a reported discrepancy between barrier heights deduced from photothreshold, C-V and I-V characteristics of WGaAs and AuGaAs Schottky barriers. A relatively constant excess temperature T0 (i.e., ln I ∝ (T + T0) when V ⪢ kT/q) is predicted in the case of large Eb/E0 0 in the higher kT/E0 0 range where thermionic emission is nearly predominant. I ∝ [exp(qV/kT) − 1] is shown to be a general expectation for all Schottky barriers near zero bias when the I-V characteristic is dominated by either thermionic or thermionic-field emission. The assumption of a Gaussian energy distribution of carriers leads to values for the slope of ln I vs. V in reasonable agreement with the results of the computer analysis, but the prediction of the absolute value of the current density deviates rapidly from the computed value when kT/E0 0 departs appreciably from unity. The Gaussian distribution also does not provide the smooth transition from T-F to thermionic emission characteristic of the computer solution.

A technique for directly plotting the inverse doping profile of semiconductor wafers

Abstract: A new technique for plotting doping profiles of semiconductor wafers is described. This technique involves driving a Schottky diode deposited on the surface with a small constant RF current (a few hundred microamperes at 5 MHz). The depth of the depletion layer is varied by changing the dc bias, but this is the only role of the dc voltage. The inverse doping profile n-1(x) is obtained by monitoring the voltage across the diode at the fundamental frequency, which is proportional to the depth x, and the second harmonic voltage, which is proportional to n-1. This type of plotter has the advantages of simplicity, high resolution (limited only by the Debye length in most cases), immediate results, and economy.

Surface State and Interface Effects on the Capacitance‐Voltage Relationship in Schottky Barriers

Abstract: In the presence of an interfacial layer and semiconductor surface states, a Schottky barrier height φb decreases with increasing electric field E at the surface of the semiconductor. If the semiconductor doping concentration Nd is uniform throughout the depletion region and if [ (qNd/e) (dφb/dE)−E] [ (d2φb/dE2) (dE/dV) ]≪1, where V is the applied voltage and e is the semiconductor permittivity, the slope of the (capacitance)−2 vs voltage relationship is constant and can be interpreted to give Nd. The voltage intercept of the relationship yields an apparent barrier height φa related to the true barrier φb by φa=φb−E (dφb/dE) + (qNd/2e) (dφb/dE)2, where q is the electron charge. From the measured variation of φa with Nd and one absolute measure of φb at one value of Nd, φb(E), and dφb(E)/dE may be deduced. From dφb(E)/dE the surface state density as a function of energy in the bandgap and the minimum value of interface thickness divided by relative interface permittivity can be obtained. Using the data of Archer and Atalla for vacuum cleaved Au‐Si diodes to illustrate our method, the surface state density is found to peak at a value of ∼2×1014 cm−2·eV−1 at about 0.83 below the conduction band and the minimum value of interface thickness divided by relative dielectric constant is found to be of the order of 5 A. Criteria are given which show how Schottky diode capacitance‐voltage data may be further used, in conjunction with photoelectric barrier measurements, to detect the presence of deep lying impurities or the penetration of surface state charge into the body of the semiconductor.

The Effect of Trapping States on Tunneling in Metal Semiconductor Junctions

Abstract: The tunneling behavior of Schottky barriers has been investigated by several authors. The I‐V characteristics exhibit an exponential form in the forward direction which can be used to determine the energy vs complex momentum dispersion relation for charge carriers in the forbidden gap. In this paper we show that under proper conditions the presence of traps can increase the tunneling probability and result in a reduction in the slope of the log I vs V characteristic by a factor of 2.

Tunneling in CdTe Schottky Barriers

Abstract: The tunneling characteristics of metal contacts on n−CdTe have been measured. Both the forward- and reverse-bias characteristics are in good agreement with the two-band model for the energy-complex-momentum relationship. The presence of trapping states increased the magnitude of the tunneling current at low levels by providing a two-step transition. The slope of the forward-bias log_e J−versus−V curves for tunneling through the intermediate states was reduced by a factor of 2.

p-n junction—Schottky barrier hybrid diode

Abstract: A new fabrication technique for passivated silicon Schottky barrier diodes is described. It is shown that the p-n junction guard ring or "hybrid" approach produces Schottky barriers whose forward and reverse electrical characteristics are in excellent agreement with simple theory, and that the excess noise normally found in passivated Schottky barrier diodes has been significantly reduced. The influence of metal barrier height and diffusion profile on the charge storage characteristics of these devices is discussed and examined experimentally.

Transport Properties of Metal-Silicon Schottky Barriers

Abstract: Schottky barrier diodes were fabricated by vacuum depositions of Au, Ag, and Cu onto chemically cleaned silicon surfaces and their current-voltage and capacitance-voltage characteristics were investigated in details over a temperature range between 100°K and 350°K. The current-voltage characteristics obtained are of nearly ideal Schottky barrier type and the current transport in the barriers is dominated by the thermionic emission and the image force effect. The temperature coefficient of the barrier height, the forward "n", and the image force dielectric constant were found to be (2.67±0.60)×10-4 eV/°K, 1.01~1.02, and 11.5e0 respectively. The departure from the ideal characteristics was explained by the generation-recombination current in the barrier region.

GaAs SCHOTTKY BARRIER AVALANCHE PHOTODIODES

Abstract: Uniform avalanche Schottky barrier photodiodes have been fabricated by plating a thin layer of platinum on GaAs and forming a guard ring by proton radiation. Operating at a gain of 100 these photodiodes exhibit gain‐bandwidth products greater than 50 GHz and enhanced signal to noise ratio in excess of 30 dB. The observed variation on the spectral response with bias can be accounted for by a change in the absorption of the Schottky barrier diode.

Schottky Barriers on GaAs

Abstract: The forward current of Schottky barriers on n-type GaAs is investigated as a function of electron concentration in the range of 8×10^17 to 8×10^18 cm^−3 at temperatures 297-4.2°K. Both vacuum-cleaved and chemically polished surfaces are used. The majority of the junctions studied are gold Schottky barriers, but tin and lead contacts are also examined. The predominant current mechanism is field emission at liquid-nitrogen temperature and below for the range of electron concentrations used. These data are in excellent quantitative agreement at 77°K with the field-emission analysis of Padovani and Stratton if one uses a two-band model for the imaginary wave number kn. At 297°K, thermionic field emission predominates, but for an electron density above 3×1018 cm−3 the field-emission mechanism with a two-band model still gives reasonable agreement.

Alternating Current Electrical Properties of Evaporated Molybdenum Oxide Films

Abstract: The limitations of dc measurements on doped thin film metal-insulator-metal structures are discussed, particularly in regard to the identification of the band structure of such systems. It is shown that the use of ac techniques provides a much wider scope of measurements which can be used to determine information about the energy diagram of thin film insulators. Furthermore such measurements have prominent characteristics which may be related to the band structure of the sample. The technique has been applied to evaporated Au–MoO3–Au samples, the capacitance of which are found to be extremely temperature sensitive; capacitance changes of 50:1 over 100 °C temperature range are reported. At low temperature the capacitance corresponds to the geometric capacitance, but at high temperatures is independent of the film thickness. The results are explained in terms of Schottky barriers at the Au–MoO3 interfaces, and the energy diagram of the system clarified. The doping density in the MoO6 is estimated to be abou...

Thermionic‐field resistance maxima in metal‐semiconductor (schottky) barriers

Abstract: A maximum in the differential resistance versus applied bias relationship of metal‐semiconductor contacts is predicted to occur when current flow is predominantly by thermionic‐field (thermally excited tunnel) emission. The predicted resistance peaks are generally asymmetrical with respect to voltage and may occur on either side of zero bias. The peak location has only an indirect correlation with the Fermi kinetic energy in the semiconductor. The theoretical approach is generally applicable to any metal‐semiconductor system when the dominant carrier flux is associated with the tail of a Fermi‐Dirac distribution. The theory is in reasonable agreement with recent experimental resistance measurements on Cr–Si Schottky barrier diodes at 77°K.

Radiation Effects on Silicon Schottky Barriers

Abstract: Because of a variety of important new applications, it is desirable to determine the effects of radiation on silicon Schottky barrier diodes. In the present study, both neutron and low-energy electron irradiation were employed and a variety of Schottky diode structures were investigated. These included the p-n junction guard ring structure and a gate-controlled structure which was used to separate surface from bulk effects. The two main effects of low-energy electron irradiation are: increase of surface recombination velocity and buildup of a positive space charge in the oxide. These results are consistent with previous studies of p-n junction diodes. For Schottky diodes without gate electrodes, the breakdown voltage is decreased and some excess current is present at low forward bias after irradiation. The effects of nuclear irradiation are (in addition to the surface effects mentioned above): decrease of bulk lifetime and carrier removal, again consistent with previous studies on p-n junction devices. Recombination-generation current increases manyfold due to the decrease in lifetime after irradiation. This component of current is important for Pt Schottky diodes which have a high barrier (0.85 eV). However, for Al diodes, since the barrier is relatively low (0.69 eV) and the thermionic emission current relatively high, recombination-generation current is not important until very high neutron dosage.

Schottky-barrier diode process and devices

Abstract: A SCHOTTKY-BARRIER DIODE CAPABLE OF EXHIBITING SUPERIOR REVERSE-BIAS OPERATING CHARACTERISTICS AND PARTICULARLY SUITABLE FOR LARGE-SCALE INTEGRATION CAN BE FABRICATED BY A METHOD COMPATIBLE WITH STANDARD SEMICONDUCTOR PROCESSING TECHNIQUES. BRIEFLY, A HIGHLY CONDUCTIVE METALLIC LAYER OVERLYING A REGION OF SEMICONDUCTOR MATIERAL IS HEATED TO A TEMPERATURE SUFFICIENT TO ENABLE SOLID-STATE DIFFUSION TO OCCUR BETWEEN THE SEMICONDUCTOR AND METAL, BUT BELOW THE EUTECTIC POINT OF BOTH. A METAL-SEMICONDUCTOR JUNCTION IS THEREBY FORMED, WHEREIN THE JUNCTION LIES BELOW THE ORIGINAL SURFACE OF THE SEMICONDUCTOR REGION BUT HAS AN EDGE AT THE SURFACE, AND UNWANTED IMPUJRITIES ARE PREVENTED FROM INTERFERING WITH OPERATION.

SB-IGFET, II: An ion implanted IGFET using Schottky barriers

Abstract: Insulated-gate field-effect transistors have been made, which combine the advantages inherent to Schottky barrier source and drain electrodes with ion implantation. This device has a self-aligned gate structure achieved by using the thick gate electrode as a mask during the ion implantation process.

Low-power bipolar transistor memory cells

Abstract: Low- and high-barrier Schottky diodes have been combined with bipolar transistors to produce planar integrated-circuit low-area memory cells that hold at 75 /spl mu/W. Low-barrier diodes formed on p-type ion-implanted silicon (10/SUP 17/ cm/SUP -3/) are used as high-resistance collector loads. High-barrier diodes formed on n-type epitaxial silicon (10/SUP 16/ cm/SUP -3/) provide low-capacitance low-leakage coupling to digit lines in a memory array. The highly reproducible rhodium silicide on silicon Schottky diodes, as well as high-quality ohmic contacts, are formed in one sequence of sputtering and high-temperature operations. The process is fully compatible with beam-lead technology. It is estimated that a 512-word memory module using these cells would operate at a 60-ns READ or WRITE cycle time.

Tunneling in Schottky Barrier Rectifiers

Abstract: When a metal is brought into intimate contact with a semiconductor there sometimes arises a potential barrier within the semiconductor which impedes the flow of electrons between it and the metal. The formation of such Schottky barriers will be described by Professor Mead and this chapter will be mainly concerned with the tunneling of electrons through them. Clearly, if a bias is applied between a metal and a semiconductor, current will flow. If the barriers are sufficiently thin and the temperature is sufficiently low, then the current flow will be primarily by electron tunneling. Conversely, for thicker barriers and higher temperatures the current flow will be due to thermionic emission over the barrier. We will also consider intermediate ranges of thickness and temperature, where the current is primarily due to tunneling of thermally excited carriers. This is the socalled TF emission first introduced by Dolan and Dyke (1) in connection with field emission from a metal tip.

Possible sources of error in the deduction of semiconductor impurity concentrations from Schottky-barrier (C, V) characteristics

Abstract: Experimental results are presented which show that surface contamination due to the method of preparation and bulk trapping centres can have a first-order effect on semiconductor impurity concentration measurements using Schottky barriers. A criterion is established which allows the reliability of the measurements to be assessed, and a method is given for measuring the impurity concentration in the presence of traps.

Low-frequency noise in Schottky-barrier diodes

Abstract: Silicon Schottky-barrier diodes have been developed which simulate the performance of point-contact (1N23WE) diodes in the standard mounts. These diodes along with 1N23 point-contact and back diodes were examined under 9.375 GHz excitation for noise temperature over the IF range of 5 kHz to 180 kHz. The Schottky diodes had noise temperatures comparable to and often lower than the back diodes. This fact, together with lower conversion loss and convenient impedance levels, makes the Schottky-barrier diodes generally advantageous in Doppler radars and similar applications.

Recent Developments in Millimeter Wave Components

Abstract: Several noteworthy improvements in the state-of-the-art of millimeter wave receiver components have been obtained which are to be reported in this paper. Planar, passivated, GaAs Schottky barrier diodes with very high frequency cut-off characteristics have been developed, and regularly reproduced. These diodes, having f/sub co/ /spl ap/ 1000 GHz at zero bias, have been tailored for use in a line of mixers that covers the 26.5 GHz to 110 GHz range with a typical conversion loss of 5.5 dB at 35 GHz and 8.0 dB at 94 GHz. Mixer noise ratio typically is 1.2 or better for all units. Currently available designs have IF passbands of 100 - 500 MHz, 0.5 - 1.0 GHz, and 1.0 - 2.0 GHZ. The very high f/sub co/ of the diodes has allowed the development of an uncooled degenerate parametric amplifier which has attained a noise figure of 1.7 dB while operating with a gain of 15 dB and an instantaneous signal bandwidth of greater than 800 MHz. The center frequency of the amplifiers is in the 30 - 35 GHz range. The pump power required for full band operation is 10 - 20 mw. The GaAs Schottky barrier diodes have also been designed into several baseband detectors. When biased optimally, an improvement of some 20 - 30 dB in tangential signal sensitivity (TSS) can be obtained in the 70 - 90 GHz range over the TSS available from a biased bolometer and narrow band detector amplifier. Typically the TSS = -51 dBm at 35 GHz and -40 dBm at 94 GHz with a video bandwidth of 10 MHz.

Negative resistance avalanche diodes with schottky barrier contacts

Abstract: A negative resistance avalanche diode comprises only a bulk semiconductor wafer contained between opposite Schottky barrier contacts.

High sensitivity radiation detector

Abstract: A photodetector diode operating with avalanche characteristics is energized through a regulator which, when the temperature of this diode varies, compensates for this variation by acting upon the energizing voltage to the diode. A reference diode having electrical characteristics equivalent to those of the detector diode and being thermally coupled to this detector diode furnishes for this purpose a reference signal to which the energizing voltage of the detector diode is coordinated by means of a differential amplifier and by means of the regulator.

Zinc sulfide Schottky barrier ultra-violet detectors

Abstract: Zinc sulfide Schottky barrier photodiodes have been fabricated and evaluated as u.v. detectors. The absolute quantum efficiency of the Schottky barriers formed by the evaporation of silver, gold, or chromium on polished n-type zinc sulfide was measured for radiation between 3500 and 1800 A. these detectors have negligible response to wavelengths longer than 3500 A which correspond to energies less than the band gap of the zinc sulfide. Chromium and gold on zinc sulfide resulted in barriers with maximum quantum efficiencies greater than 50 per cent at 3250 A, while the quantum efficiencies were greater than 20 per cent at 1800 A. Still higher quantum efficiencies, 70 per cent, were measured for silver-zinc sulfide barriers due to the transmission “window” in silver near 3225 A. Calculations of the fraction of the radiation, incident on the silver, which enters the zinc sulfide have been compared with measured quantum efficiencies of these diodes. This comparison indicated that, within experimental error, all the carriers generated within the zinc sulfide contribute to the photocurrent.

Fast switching pnp transistor

Abstract: The on-off switching time of a PNP transistor is significantly decreased by placing a Schottky Barrier diode in parallel with the collector-base PN junction of the transistor.

Au-Cu Alloy and Ag-Cu Alloy-Silicon Schottky Barriers

Abstract: Schottky barriers formed by vacuum depositions of Au-Cu and Ag-Cu alloys on n-Si (111) surfaces were investigated. The barrier height of the two systems changes in a linear fashion with the composition of the alloy as found in Au-Ag alloy-Si contacts. The linear variation of the barrier height with composition is attributed to a corresponding composition dependence in the work function of the alloy.

Insulated gate field effect transistor with integrated safety diode

Abstract: An insulated gate field effect transistor with an integrated safety diode is described. The safety diode comprises opposite-type conductivity diode zones forming a low breakdown voltage PN-junction by reason of high dopant concentrations in the diode zones. The diode zone which is of the same type conductivity as the substrate completely surrounds the other diode zone and can thus serve as a channel interrupter preventing parasitic transistor action between the safety diode and the active zones of the field effect transistor. Other features include location of the diode zone of the same type conductivity as the substrate contiguous with the source electrode, and a metal layer on the surface short circuiting the PN-junction therebetween to directly connect the source to one of the zones of the safety diode.