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.     

基于平面肖特基二极管的W波段检波器

肖特基二极管技术为常温下毫米波信号的检测提供了有效的解决方案。它具有极低的寄生电容和级联电阻,可用于该频段的倍频器、混频器和检波器当中。相比于Galey Cell和热辐射测定器(Bolometer),基于肖特基二极管的直接检波技术具有低噪声、高反应率和常温使用的特点。本文介绍了一种基于波导结构的零偏置肖特基二极管检波器,采用E面探针传输波导基模电磁波,通过阻抗匹配实现微带线到二极管的耦合。测试结果表明,在-30 dBm输入功率下：电压反应率的峰值可达8 900 V/W;在75 GHz~105 GHz的频率范围内,电压反应率在1 000 V/W以上。     

ZnS-based visible-blind UV detectors: Effects of isoelectronic traps

The aim of this study is to reveal the underlying cause of the gradual turn-on characteristic of low Te containing ZnSTe Schottky barrier photodiodes. The results of photoresponse studies on ZnS, ZnSSe and ZnSTe diodes indicate that the Te isoelectronic trapping effect is responsible for the gradual turn-on characteristic of low Te containing ZnSTe Schottky barrier photodiodes. The results also reveal that the ZnSSe diode, having the advantage of being free of isoelectronic centers, is a more suitable choice for applications requiring high visible rejection power. It is demonstrated that highly UV sensitive responsivity with an abrupt long wavelength cutoff tailored to lie between 340–400 nm can be achieved in the ZnSSe diode system.     

Numerical simulation study of current–voltage characteristics of a Schottky diode with inverse doped surface layer

The Poisson’s equation and drift–diffusion equations are used to simulate the current–voltage characteristics of Schottky diode with an inverse doped surface layer. The potential inside the bulk semiconductor near the metal–semiconductor contact is estimated by simultaneously solving these equations, and current as a function of bias through the Schottky diode is calculated for various inverse layer thicknesses and doping concentrations. The Schottky diode parameters are then extracted by fitting of simulated current–voltage data into thermionic emission diffusion equation. The obtained diode parameters are analyzed to study the effect of inverse layer thickness and doping concentration on the Schottky diode parameters and its behavior at low temperatures. It is shown that increase in inverse layer thickness and its doping concentration give rise to Schottky barrier height enhancement and a change in the ideality factor. The temperature dependences of Schottky barrier height and ideality factor are studied. The effect of temperature dependence of carrier mobility on the Schottky diode characteristics is also discussed.     

Effect of Inverse Doped Surface Layer in Schottky Barrier Modification: A Numerical Study

Poisson’s equation and the drift–diffusion equations are used to simulate the current–voltage characteristics of a Schottky diode with an inverse doped surface layer. The potential inside the bulk semiconductor near the metal–semiconductor contact is estimated by simultaneously solving these equations, and then current as a function of bias through the Schottky diode is calculated. The Schottky diode parameters are extracted by fitting of simulated data to the thermionic emission diffusion equation. The simulation is carried out for various inverse layer thicknesses and doping concentrations. The obtained diode parameters are analyzed to study the effect of the inverse layer thickness and doping concentration on Schottky diode modification and its behavior at low temperatures. It is shown that an increase in the inverse layer thickness and doping concentration leads to Schottky barrier height enhancement and a change in the ideality factor. The temperature dependences of the Schottky barrier height and ideality factor are also studied.     

Schottky Barrier Characteristics of Cobalt–Nickel Silicide/n-Si Junctions for Scaled-Si CMOS Applications

Ternary cobalt–nickel silicide/n-Si Schottky diodes have been fabricated by sputtering using an equiatomic cobalt–nickel alloy target. A minimum sheet resistivity of the ternary silicide is found to be 5–7 $Omega / hbox{sq}$. Grazing-incidence X-ray diffraction shows the formation of ternary silicide phases. Cross-sectional TEM micrograph shows a fairly uniform diffusion of metals into Si with the formation of fully silicided film. Selected-area electron diffraction pattern exhibits the crystalline nature of the silicide layer. Temperature-dependent electrical current–voltage measurements have been used to characterize an optimized Schottky diode formed by annealing at 450 $^{circ}hbox{C}$. The room-temperature barrier height and ideality factor are found to be 0.656 eV and 1.6, respectively, from the $I$ –$V$ characteristics. The series resistance of the diode has been calculated and is found to be 1–11.8 $hbox{k}Omega$ . The variation of barrier height has been attributed to the inhomogeneity in Schottky junction.      

两种结构GaN基太阳盲紫外探测器

分别在金属有机化学汽相沉积（MOCVD）生长的i-Al0.33Ga0.67N／AlN／n-GaN和p-Al0.45Ga0．55N／i—Al0.45Ga0.55N／n＋-Al0.65Ga0.35N的异质结构上,成功研制了太阳盲区的肖特基型和PIN型紫外探测器。研究结果表明,Au与i—Al0.33Ga0.67N形成了较好的肖特基结,响应波长从250—290nm,峰值（286nm）响应率约为0．08A／W;PIN型紫外探测器的响应波长从230～275nm,峰值（246nm）响应率约为0．02A／W。     

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     

An amorphous SiC/Si heterojunction p-i-n diode for low-noise andhigh-sensitivity UV detector

The authors report the UV photoresponse of an a-SiC/a-Si heterojunction p-i-n diode with the structure of glass/TCO (transparent conducting oxide, SnO₂:F)/p-a-SiC:H/i-a-Si:H/n-a-Si:H/Al. The diode has been designed for a high-sensitivity and low-noise UV detector. The diode has its peak responsivity (0.254 A/W) and quantum efficiency (81.5%) at 385 nm. This structure possesses (1) the window effect by using the wide-bandgap a-SiC:H as the front layer (p-layer) and (2) the carrier confinement effect at the p-SiC:H/i-a-Si:H interface. Enhancements are proposed to raise UV response and suppress long-wave responsivity. The diode was designed to be operated under zero external bias to suppress the dark-current-induced noise. Results show a 200% higher UV sensitivity than a GaAsP Schottky photodiode in the 200-400-nm wavelength region     

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.     

Numerical analysis of inhomogeneous Schottky diode with discrete barrier height patches

The potential profile inside the semiconductor at the metal–semiconductor contact is simulated by numerically solving the Poisson equation and the drift diffusion equations for inhomogeneous Schottky diode. From the simulated potential and the electron and hole concentrations, the drift-diffusion current as a function of bias is calculated. The simulation is carried out for various distribution patterns of barrier height patches at the metal–semiconductor contact to study the effect of barrier inhomogeneities on the Schottky diode parameters, namely barrier height and ideality factor and their temperature dependence. It is found that barrier height decreases and ideality factor increases with increase in the deviation of discrete barrier height patches in the distribution. The resulting barrier parameters are studied to understand the effect of barrier inhomogeneities on the current–voltage characteristics of inhomogeneous Schottky contact.     

p-GaN/Al0.35Ga0.65N/GaN应变量子阱肖特基紫外探测器

报道了p-GaN/Al0.35Ga0.65N/GaN应变量子阱结构的肖特基紫外探测器的制备及性能.器件的测试结果表明,在p-GaN/Al0.35Ga0.65N/GaN双异质结中强烈的压电极化和Stark效应共同作用下使得器件在正偏和反偏时的响应光谱都向短波方向移动了10nm.零偏下器件在280nm时的峰值响应为0.022A/W,在反向偏压为1V时,峰值响应增加到0.19A/W,接近理论值.在正向偏压下器件则呈平带状态,并在283和355nm处分别出现了两个小峰.在考虑极化的情况下,通过器件中载流子浓度分布的变化解释了器件在不同偏压下的响应特性,发现p-GaN/Al0.35Ga0.65N/GaN中的极化效应对器件的响应特性影响很大,通过改变偏压和适当的优化设计可以使探测器在紫外波段进行选择性吸收.     

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.     

High temperature annealing behaviour of Schottky barriers on GaAs with gold and gold-gallium contacts

It is shown that unlike AuGaAs Schottky diodes, a Schottky barrier made on GaAs using an evaporated film of AuGa eutectic alloy does not degrade on heat treatment. It is shown that the presence of Ga in the top contact prevents micro-alloying to take place during heat treatment and thus prevents degradation of the diode behaviour.     

Effect of KOH treatment on the Schottky barrier inhomogeneity in Ni/n-GaN

The effect of KOH treatment on the Schottky barrier inhomogeneity in Ni/n-GaN Schottky diodes was investigated. It was observed that both the barrier heights and ideality factors varied from diode to diode with a linear relationship between barrier height and ideality factor, indicating the presence of a lateral inhomogeneity in the Schottky barrier. Simple extrapolation of the straight line obtained from the linear fitting to the barrier height versus ideality factor plot to the image-force controlled ideality factor produced the lateral homogeneous barrier heights, which were higher than those from current–voltage measurements. Furthermore, Gaussian fitting to the distribution of barrier heights exhibited the increased barrier height with the smaller standard deviation after KOH treatment, implying the improved barrier homogeneity. A possible explanation for this behavior can be an improvement of the Ni/n-GaN interface intrinsic properties, e.g., through a reduction of the surface states acting as low barrier region.     

Barrier height diminution in Schottky diodes due to electrostatic screening

Electrostatic screening in the metal contact of a Schottky (metal-semiconductor) diode is shown to influence the calculated electrical characteristics of the diode. A thin space-charge layer is formed at the surface of the metal contact by capacitively induced free charges, This results in a voltage dependent diminution of the barrier height of the diode that increases in magnitude with increasing semiconductor dielectric constant and carrier concentration. Predicted values of the barrier height diminution exceed those attributed to image forces or tunneling effects for materials with dielectric constants greater than about 20. In diodes using semiconducting ferroelectric or piezoelectric materials, an additional diminution of the barrier height results from free charges induced in the metal contact by a remanent polarization field or an externally applied mechanical stress. Current-voltage characteristics of a metal-semiconductor diode are shown to be significantly influenced by the electrostatic screening effect. A soft breakdown current as opposed to saturation current is predicted for reverse biases while an exponential forward current with an η coefficient exceeding unity is predicted for forward biases. Photoemission characteristics are also affected. A voltage-dependent diminution of the threshold energy for photoresponse is predicted. Capacitance-voltage characteristics, on the other hand, differ only slightly from those of an ideal Schottky diode except in the case of a ferroelectric diode where excessively large screening effects are possible.     

Temperature-dependence of barrier height of swift heavy ion irradiated Au/n-Si Schottky structure

The electrical characteristics of swift heavy ion (SHI) irradiated Au/n-Si (1 0 0) structure has been investigated in a wide temperature range (50–300 K). The forward bias current–voltage (I–V) measurements have been used to extract the diode parameters as a function of temperature. The Zero-bias Schottky barrier height decreases with decreasing temperature. However, the flat-band barrier height is almost independent of the temperature. These results are interpreted using the models of Fermi level pinning. The behavior of Schottky diode parameters is explained by taking into account the role of the irradiation induced defects at Au/n-Si (1 0 0) interface.     

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.     

Current–voltage characteristics of Schottky diode simulated using semiconductor device equations

The Poisson's equation and the drift diffusion equations have been used to simulate the current–voltage characteristics of Schottky diode. The potential variation inside the bulk semiconductor near the metal–semiconductor contact was estimated first and then the current as a function of bias through the Schottky diode using silicon parameters were calculated over a wide temperature range. From the simulated current–voltage characteristics the diode parameters were extracted by fitting of current–voltage data into thermionic emission diffusion current equation. The derived barrier parameters are analysed to study the effect of various parameters, e.g. semiconductor thickness, doping concentration, temperature dependence of carrier mobility and energy band gap, on the current–voltage characteristics of Schottky diode in view of the thermionic emission diffusion current equations.