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.     

面向太赫兹应用的InP基肖特基二极管

Based on characteristics such as low barrier and high electron mobility of lattice matched In_0.53Ga_0.47 As layer,InP-based Schottky barrier diodes（SBDs） exhibit the superiorities in achieving a lower turn-on voltage and series resistance in comparison with GaAs ones.Planar InP-based SBDs have been developed in this paper.Measurements show that a low forward turn-on voltage of less than 0.2 V and a cutoff frequency of up to 3.4 THz have been achieved.The key factors of the diode such as series resistance and the zero-biased junction capacitance are measured to be 3.32Ωand 9.1 fF,respectively.They are highly consistent with the calculated values.The performances of the InP-based SBDs in this work,such as low noise and low loss,are promising for applications in the terahertz mixer,multiplier and detector circuits.     

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.     

Low-parasitic, planar Schottky diodes for millimeter-waveintegrated circuits

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 μm² and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Ω. Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested     

Deep traps in ideal n-InP Schottky diodes

A number of deep electron trap levels have been detected in bulk and epitaxial InP for the first time. These deep traps are located in the upper half of the bandgap, and have been observed in Schottky barrier diodes by transient capacitance spectroscopy (d.l.t.s.). The deep traps have been shown to be responsible for low frequency excess noise in the Schottky diodes.     

New approach to the design and the fabrication of THz Schottkybarrier diodes

GaAs Schottky barrier diodes with near-ideal electrical and noise characteristics for mixing applications in the terahertz frequency range are described. The conventional formulas describing these characteristics are valid only in a limited forward bias range, corresponding to currents much smaller than the operating currents under submillimeter mixing conditions. Therefore, generalized analytical expressions for the I-V and C-V characteristics of the metal-semiconductor junction in the full bias range are given. A new numerical diode model is presented which takes into account not only the phenomena occurring at the junction, such as current dependent recombination and drift/diffusion velocities, but also the variations of electron mobility and electron temperature in the undepleted epi-layer. A diode fabrication process based on the electrolytic pulse etching of GaAs in combination with an in situ platinum plating for the formation of the Schottky contacts is described. Schottky barrier diodes with a diameter of 1 μm fabricated by this process have already shown excellent results in a 650-GHz waveguide mixer at room temperature     

Schottky diode for bipolar LSI's consisting of an impurity-controlled Si substrate and Al(2%Si) electrode

Circuit design conditions of Schottky diodes have been investigated and the fabrication method for diodes suitable for the conditions has been proposed for applications to bipolar LSI's, such as ECL RAM and Schottky TTL. It has been found that the desired Schottky diode for bipolar LSI's is not an ideal device from the theoretical point of view. Desired built-in voltage, ideal factor, series resistance, and junction capacitance for the Schottky diode have been estimated, respectively, for the bipolar RAM and Schottky TTL. A proposed Schottky diode consists of an impurity-concentration-controlled     

一种精确检测半导体二极管正向电特性的新方法

提出了一种基于串联模式精确地检测半导体二极管正向电特性的新方法.利用该方法,不仅可以得到二极管在不同电压下的串联电阻、结电容、结电压、理想化因子等值,还能判断一个实际的二极管有无界面层存在并得到其界面层阻抗值.用此方法对Ni/ n- Ga N肖特基二极管进行了检测,所有的实验结果与理论分析相符合.实验中确认了在Ga N肖特基二极管中结的负电容和具有非线性电阻和电容的界面层的存在.     

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.     

用弹道电子发射显微术研究超薄金属硅化物/硅肖特基接触

采用弹道电子发射显微术 ( BEEM)技术对超薄 Pt Si/Si、Co Si2 /Si肖特基接触特性进行了研究 ,并与电流 -电压 ( I- V)及电容 -电压 ( C- V)测试结果进行了对比 .研究了 Ar离子轰击对超薄Pt Si/n- Si肖特基接触特性的影响 .BEEM、I- V/C- V技术对多种样品的研究结果表明 ,I- V/C- V测试会由于超薄硅化物层串联电阻的影响而使测试结果产生严重误差 ;BEEM测试则不受影响 .随着离子轰击能量增大 ,肖特基势垒高度降低 ,且其不均匀性也越大 .用 BEEM和变温 I- V对超薄 Co Si2 /n- Si肖特基二极管的研究结果表明 ,变温 I- V测试可在一定程度上获得肖特基势垒     

Enhancement in electrical properties of Au/n-GaAs Schottky diodes exposed to 60Co gamma rays

The effect of γ-ray exposure on the electrical characteristics of Au/n-GaAs Schottky barrier diodes has been investigated using current–voltage and capacitance–voltage techniques. The results indicate that irradiation with a cumulative dose of 10 Mrad (Si) improves the electrical characteristics of the diode. The parameters like ideality factor, series resistance and reverse leakage current determined from the current–voltage data decreases, whereas the barrier height and rectification ratio increases upon irradiation. The effective barrier height deduced from the capacitance–voltage technique has also increased with irradiation. The irradiated diode shows a higher carrier concentration compared to the virgin diode. The observed overall improvement in the diode quality is attributed to the annealing effect of γ-rays.     

A method for measuring the shot noise in Schottky diodes with reduced barrier height

A method for measuring the spectral density of shot noise of one-port networks, in particular, semiconductor diodes, is described. The method is applicable at frequencies of up to 200 MHz. Expressions are obtained that relate the spectral density of the diode’s current noise to the measured noise factor and power gain of the diode fixture with the diode mounted in it. With this method, the dependence of the Fano factor of a GaAs Schottky diode with reduced barrier height on the diode current is determined.     

Analysis and Optimization of Millimeter-And Submillimeter-Wavelength Mixer Diodes

An analysis of the noise of millimeter- and submillimeter-wavelength mixers with GaAs Schottky diodes is presented. This analysis accounts for the correlation of the downconverted components of the time-varying hot-electron noise in the series resistance, and is thus accurate even for cryogenically cooled mixers operated at submillimeter wavelengths. This paper shows that the terms of the series-resistance noise correlation matrix are functions of the Fourier coefficients of the squared diode current F(I/sup 2/) rather than the square of the Fourier coefficients of the diode current [F(I)]/sup 2/, as has been previously presented in the literature. The analysis is used to evaluate the optimization of cryogenic mixer diodes. It is shown that minimization of the diode's I-V slope parameter V/sub 0/ is more critical than reduction of the parasitic elements for millimeter-wavelength operation, while at frequencies above 600 GHz (Lambda<0.5 mm), the junction capacitance is the most crucial parameter. Experimental results from several research groups working with a variety of mixers are presented to substantiate these results.     

碳化硅器件发展概述

概要介绍了第三代半导体材料碳化硅(SiC)在高温、高频、大功率器件应用方面的优势,结合国际上SiC肖特基势垒二极管,PiN二极管和结势垒肖特基二极管的发展历史,介绍了SiC功率二极管的最新进展,同时对我国宽禁带半导体SiC器件的研究现状及发展方向做了概述及展望。     

Hyperabrupt junctions in Au-Si Schottky diodes by ion implantation

The application of ion implantation to the fabrication of Au-Si Schottky diodes with highly nonlinear capacitance/voltage characteristics is described. The capacitance/voltage characteristic and the derived impurity profile are given for a typical diode. The forward current/voltage characteristics are described, and an estimate of Au-Si barrier height is made.     

On the voltage‐dependent series resistance of a planar Schottky barrier diode

The series resistance of a planar Schottky barrier diode fabricated on p‐type silicon is investigated by analysing the current–voltage characteristics of the device. Different characterisation techniques have been applied to obtain the value of the series resistance of the device. It is found that the existing techniques are either not applicable for the present device or yield unreliable value for the series resistance. A numerical analysis of the I–V data reveals unusual voltage dependence of the series resistance of the device. The anomaly has been resolved by postulating a potential barrier at the ohmic contact and drawing analogy to serially connected high‐ and low‐barrier diodes in a back‐to‐back configuration. It is found that the voltage dependence of the series resistance of the device can be described by certain empirical law, which also applies to device on GaN. The measured voltage behaviour of the ac resistance and capacitance of the device at different frequencies have been found to be consistent with those of a serial combination of diodes considered to verify the postulate made in interpreting the I–V data.     

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.     

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.