A MoSi2Schottky diode for bipolar LSI's

Fabrication and characterization of a molybdenum silicide Schottky diode have been investigated for its application to large-scale bipolar logic LSI's using a Schottky TTL. The diode consists of a silicon     

Transistor Schottky-barrier-diode integrated logic circuit

A new high-speed low-power logic circuit using Schottky barrier diodes to avoid saturation of bipolar transistors is described. An experiment using discrete devices and a theoretical calculation show the possibility of subnanosecond logic using a saturated-type transistor logic circuit. A theoretical comparison with CML shows a 2:1 advantage in the speed-power product. The compatibility of Schottky barrier diode with monolithic silicon integrated circuit processing is shown. A prototype TTL circuit is described. Experimental results are given.     

Bipolar-mode Schottky contact and applications to high-speed diodes

A Schottky contact operation combined with minority-carrier transport, a concept of bipolar-mode Schottky contacts, is proposed. There are two bipolar-mode Schottky contacts. One acts as a minority-carrier injector causing conductivity modulation without excessive carrier accumulation, while the other operates as an ideal ohmic contact to conduct minority carriers without accumulation. Applicationally, these contacts are utilized to improve conventional Schottky diodes and p-n diodes, respectively and a high-voltage Schottky diode (BSBD) and a fast-recovery p-n diode (quasi-LLD) can then be realized.     

A new theoretical model for a p-n junction realistic diode

Attempts have been made to give a new theoretical model for semiconductor bipolar realistic diodes. The fact that the realistic devices are not completely free from the effects of traps, defects, band to band radiative and non-radiative (Auger effect) transitions etc., leads to the mathematical solutions which show oscillatory variations (between two positive values) in the carrier density distributions. This directly leads to the deviation of a diode characteristics from those of the ideal diode. An application of the model has been made to a p-n junction. Experimental evidence of this deviation in the Schottky heterostructures found in the literature can act as a direct support of the model.     

Reliability and micro-structural properties of GaAs Schottky diodes for submillimeter-wave applications

Whisker contacted GaAs Schottky barrier diodes are the standard devices for mixing and multiplier applications in the THz frequency range. This is mainly due to their minimum parasitics and mature technology. But with the decreasing size of the anode contact, which is required for operation at high frequencies (up to approx. 3 THz), the reliability and the micro-structural understanding of the Schottky barrier becomes increasingly important. This contribution presents new results concerning the reliability of Schottky diodes and the physical properties of small-area Schottky junctions, especially at low current densities. For these purposes a number of different Schottky diodes have been fabricated with different epilayer doping concentrations and anode diameters. Measured I/V characteristics show that the diode current deviates considerably from the ideal thermionic current behavior with decreasing diode diameter. This deviation shows an exponential dependence on the diode voltage and is a function of the doping concentration of the active layer. For a given doping concentration in the epi-layer and decreasing anode diameter, this phenomenon shifts the minimum of the ideality factor towards higher current densities. An explanation is given in terms of a difference of the cyrstallinity of the polycrystalline platinum films on the GaAs for decreasing SiO₂ aperture size in connection with a reduced Pt mobility in the electrolyte. The reliability of Schottky barrier diodes under thermal and electrical stress has been investigated on different THz Schottky diode structures. The results show that the barrier height and the ideality factor of the fabricated structures are not affected by thermal stress. Electrical stress induced by large forward currents up to a current density of 10 kA/mm² even leads to a slight increase of the barrier height and a reduction of the series resistance.     

A novel saturation control in TTL circuits

A novel technique of saturation control in TTL and other saturated logic circuits is described and analyzed. The approach is not only fully compatible with standard bipolar transistor technology, but lends itself to integration. The device parameter tracking on a chip is utilized to suitably bias a feedback saturation control transistor so that the stored charge of a TTL gate output transistor is reduced by typically two orders of magnitude. Thus, the turn-off switching time is significantly decreased without noticeably affecting the turn-on delay time. The performance improvement is close to that achieved by the well-known Schottky diode clamp approach; however, the novel technique offers advantages in noise margin, control of down-level output voltage, and processing. The effectiveness of the proposed technique has been verified theoretically by computer circuit analysis and experimentally by bench setup measurements.     

Design of Submillimeter Schottky Mixers Under Flat-Band Conditions Using an Improved Drift-Diffusion Model

Minimum conversion loss in millimeter and submillimeter-wave Schottky mixers is achieved when the diodes are slightly pushed into the flat-band regime. The discrepancies found between experimental results and physics-based harmonic balance simulations for a 330 GHz antiparallel diode pair subharmonic Schottky mixer showed that traditional drift-diffusion models with conventional boundary conditions at the Schottky contact do not correctly predict the behavior of the Schottky-based mixers working under flat-band conditions. In this work, we employ Monte Carlo simulations to get physical insight of the Schottky diodes working in the flat band regime. New boundary conditions obtained from this analysis have been included in our drift-diffusion simulator which has resulted in an improvement of our circuit simulator to predict mixer operation under flat band regime.      

The Mott diode as a heterodyne receiver element

This paper considers a novel doping profile for Schottky barrier mixer diodes called the Mott barrier. The structure consists of a metal-semiconductor junction in which the semiconductor's epitaxial layer is very lightly doped and thin enough so that it remains depleted even under substantial forward bias. It has been proposed that Mott barrier diodes will generate less noise and have lower series resistance-junction capacitance products than standard Schottky diodes, thus increasing the sensitivity and cut-off frequency of heterodyne receivers. In this paper, the band structure and electron transport properties of the Mott diode are evaluated. This analysis shows that the Mott diode actually will have a large series resistance-junction capacitance product and excessive hot electron noise, making it a poor candidate for high-frequency applications. Experimental results are presented which substantiate these conclusions.     

A gallium arsenide SDFL gate array with on-chip RAM

Describes a GaAs gate array with on-chip RAM based on the Schottky diode field-effect transistor logic (SDFL) technology. The array features 432 programmable SDFL cells, 32 programmable interface input-output (I/O) buffers, and four 4/spl times/4 bit static random access memories (RAM) on a 147 mil/spl times/185 mil chip. Each SDFL cell can be programmed as a NOR gate with as many as 8 inputs with a buffered or unbuffered output or as a dual OR-NAND gate with four inputs per side. The interface I/O buffer can be programmed for ECL, TTL, CMOS, and SDFL logic families. Each 4/spl times/4 bit RAM is fully decoded using SDFL circuits (depletion-mode MESFET). Preliminary results demonstrate the feasibility of GaAs SDFL for fast gate array and memory applications.     

SiC power Schottky and PiN diodes

The present state of SiC power Schottky and PiN diodes are presented in this paper. The design, fabrication, and characterization of a 130 A Schottky diode, 4.9 kV Schottky diode, and an 8.6 kV 4H-SiC PiN diode, which are considered to be significant milestones in the development of high power SiC diodes, are described in detail. Design guidelines and practical issues for the realization of high-power SiC Schottky and PiN diodes are also presented. Experimental results on edge termination techniques applied to newly developed, extremely thick (e.g., 85 and 100 μm) 4H-SiC epitaxial layers show promising results. Switching and high-temperature measurements prove that SiC power diodes offer extremely low loss alternatives to conventional technologies and show the promise of demonstrating efficient power circuits. At sufficiently high on-state current densities, the on-state voltage drop of Schottky and PiN diodes have been shown to be comparable to those offered by conventional technologies     

Low-frequency noise in Schottky barrier diodes

The low-frequency excess noise in Schottky barrier diodes has been investigated. In the ideal case where the saturation current is completely determined by thermionic emission of electrons, no 1/? noise will be produced in the barrier. The presence of trap states in the depletion region can lead to generation-recombination noise. At sufficient high forward currents 1/? noise can be generated in the series resistance of the Schottky diode. Deviations from the ideal diode, for example as a result of edge effects, produce 1/? noise and increase at the same time the ideality factor. It is empirically found that the 1/? noise level decreases very rapidly if the ideality factor tends to unity.     

A 3.5-ns, 2-W, 20-mm/SUP 2/, 16-kbit ECL bipolar RAM

A 3.5-ns emitter-coupled logic (ECL) 16-kbit bipolar RAM with a power dissipation of 2 W, a cell size of 495 /spl mu/m/SUP 2/, and a chip size of 20 mm/SUP 2/ has been developed. High performance is achieved using a high-speed Schottky barrier diode decoder with a pull-up circuit and a double-stage discharge circuit for a word-line driver. Small cell size is obtained using ultra-thin Ta/SUB 2/O/SUB 5/ film capacitors and 1-/spl mu/m U-groove isolation technology. An access time of 3.5 ns in this 16-kb bipolar RAM is equivalent to an effective access time of 2.5 ns at the system level, due to an on-chip address buffer and latch.     

Performance of W-InSb Metal-Semiconductor Point-Contact Diodes as Detectors and Mixers in the Near Infrared

Metal-Insulator-Metal (MIM) and Schottky-barrier diodes have been used extensively in the past years as harmonic generators and mixers for frequency measurements in the spectral range from the far-infrared to the visible. MIM diodes present a very low fabrication cost and are easy to handle, while Schottky diodes are mechanically more stable and long-lived. In the present work we discuss the performance of a metal-semiconductor point-contact diode for the radiation around 1 μm. This device, which may be viewed as a hybrid between a MIM and a Schottky diode, combines the simplicity and easiness of fabrication of the MIM diode with the stability and the long contact life typical of the Schottky diode. It proved to be very efficient even for visible light.     

Ni，Ti/4H-SiC肖特基势垒二极管

采用本实验室生长的4H-SiC外延片,分别用高真空电子束蒸Ni和Ti做肖特基接触金属,Ni合金作欧姆接触,SiO_2绝缘环隔离减小高压电场集边效应等技术,制作出4H-SiC肖特基势垒二极管(SBD)。该器件在室温下反向击穿电压大于600 V,对应的漏电流为2.00×10~(-6)A。对实验结果分析显示,采用Ni和Ti作肖特基势垒的器件的理想因子分别为1.18和1.52,肖特基势垒高度为1.54 eV和1.00 eV。实验表明,该器件具有较好的正向整流特性。     

Comparison of the responsivity of W-Ni point contact MBM diodes with W-Si point contact Schottky diodes

The responsivities of the W-Ni point contact MBM diode and the W-Si point contact Schottky diode (commercial 1N23B diode) are compared at 9.5 GHz under identical conditions. The MBM diode has almost half the responsivity of the Schottky diode and was measured to be ≃20 V/W for a 550 Ω termination. The responsivity of the MBM diode decreases with an increase of the frequency. However, this is not due to the RC time constant of MBM diodes, but due to the antenna properties of the whisker and the relaxation behavior of the metallic whisker antenna.     

Classical infrared mixing with solid state diodes

It is shown that classical infrared diode mixing can compete with straight quantum detector diodes even if the available power gain of the diode mixer is as small as 10^?5–10^?6. To shed light on the diode mixer problem, the small signal diode detector problem is discussed, the effect of the series resistance r of the diode is dealt with and the time constants that may be operating in the device are evaluated. It is shown that Schottky barrier diodes operating in the diffusion mode are probably too slow, even though the response problem has not been solved exactly. Schottky barrier diodes operating in the thermionic mode are better; they can be understood in terms of a vacuum tube analogy, indicating that the characteristic time constant is the transit time of those electrons that just pass the barrier. Diodes operating in the tunneling mode have probably the fastest response, but an exact theory has not been developed. An interesting series resonance method is discussed that may lead to improved detector response near the resonance frequency.     

A new polysilicon process for a bipolar device—PSA technology

A new polysilicon process has been developed to obtain high packing density, high speed, and low-power LSI's. The new process, called the polysilicon self-aligned (PSA) method is based on a new fabrication concept for dimensional reduction and does not require fine patterning and accurate mask alignment. For an application example of this new method, an emitter-coupled logic (ECL) gate with 0.6 ns delay time, 0.5 pJ power-delay product, and 6400 µm²gate area has been achieved. Futhermore, by introducing a polysilicon diode (PSD) and Schottky barrier diode (SBD) to the PSA method, a low-power Schottky-diode-transistor-logic (SDTL) gate with 1.6 ns delay time, 0.8 pJ power-delay product, and 2000-µm²gate area has been successfully developed.     

Enhancement of effective barrier height in Ti-silicon Schottky diode using low-energy ion implantation

Increasing the effective barrier height in a Ti-p-type silicon Schottky diode has been achieved by means of low-energy ion implantation to introduce a thin inversion layer on silicon substrate. It is shown theoretically that effective barrier height equal to the energy bandgap can be obtained in such structure if the thickness and dopant density of the implanted layer are properly chosen. Experimental results for several titanium (Ti) on phosphorus implanted p-type silicon Schottky diodes show that effective barrier heights were increased from 0.6 eV for the Ti-p Si Schottky diode to 0.96 eV for a Ti-n-p-Si Schottky diode with a phosphorus-implanted layer thickness of 400 Å and dose of 1.26 × 10¹²cm^-2. Good agreement is obtained between the calculated and the measured barrier height for several Ti-n-p silicon Schottky diodes.     

Silicon carbide PiN and merged PiN Schottky power diode models implemented in the Saber circuit simulator

Dynamic electrothermal circuit simulator models are developed for silicon carbide power diodes. The models accurately describe the temperature dependence of on-state characteristics and reverse-recovery switching waveforms. The models are verified for the temperature dependence of the on-state characteristics, and the di/dt, dv/dt, and temperature dependence of the reverse-recovery characteristics. The model results are presented for 1500 V SiC Merged PiN Schottky (MPS) diodes, 600 V Schottky diodes, and 5000 V SiC PiN diodes. The devices studied have current ratings from 0.25 A to 5 A and have different lifetimes resulting in different switching energy versus on-state voltage trade-offs. The devices are characterized using a previously reported test system specifically designed to emulate a wide range of application conditions by independently controlling the applied diode voltage, forward diode current, di/dt, and dv/dt at turn-off. A behavioral model of the test system is implemented to simulate and validate the models. The models are validated for a wide range of application conditions for which the diode could be used.     

Low-frequency excess noise in metal—Silicon Schottky barrier diodes

Theoretical models for the generation-recombination noise and trapping noise in metal-semiconductor Schottky barrier diodes are developed. Low-frequency excess noise in Schottky barrier diodes is found to be dominated by the modulation of the barrier height φB caused by fluctuation in the charge state of traps or generation-recombination centers. This noise mechanism does not occur in p-n junctions. The bias and the temperature dependence of the generation-recombination noise is critically compared with the experimental data for forward diode current ranges from 3 to 300 µA and operating temperatures from -25° to 100°C. Trapping noise in Schottky barrier diodes is observed at low temperatures in diodes not intentionally doped with deep level impurities. The experimental results on trapping noise can be described by assuming that the trap states have a constant capture cross section and are uniformly distributed in space, as well as in energy. The surface potential at the diode periphery also has an important effect on the Schottky barrier diode noise. The best low-frequency noise behavior is found when the surface is at the flat-band condition. An accumulated surface is always associated with a large amount of low-frequency excess noise.