Absolute negative resistance and multivaluedness on current-voltage characteristics of tunnel diodes

The effect of external perturbations of large amplitude in the form of a coherent signal or noise on the behavior of dynamic and static current-voltage (I–V) characteristics of tunnel diodes has been experimentally investigated. It is shown that, when an appropriate frequency is chosen, an increase in the amplitude of the external coherent signal leads to the occurrence of multivaluedness and absolute negative resistance on the I–V characteristics of tunnel diodes. The noise effect suppresses the N-type negative differential resistance on the I–V characteristics of tunnel diodes and significantly distorts these characteristics. A possible mechanism of the occurrence of absolute negative resistance is proposed.     

Experimental demonstration of a silicon carbide IMPATT oscillator

Silicon carbide (SiC) is an excellent material for high-power and high-frequency applications because of its high critical field, high electron saturation velocity, and high thermal conductivity. In this letter, we report the first experimental demonstration of microwave oscillation in 4H-SiC impact-ionization-avalanche-transit-time (IMPATT) diodes. The prototype devices are single-drift diodes with a high-low doping profile. DC characteristics exhibit hard, sustainable avalanche breakdown, as required for IMPATT operation. Microwave testing is performed in a reduced-height waveguide cavity. Oscillations are observed at 7.75 GHz at a power level of 1 mW     

Forward current—Voltage and switching characteristics of p+-n-n+(epitaxial) diodes

The forward-biased current-voltage and forward-to-reverse biased switching characteristics of p⁺-n-n⁺epitaxial diodes are investigated. The manner in which the n-n⁺junction affects the flow of injected minority carriers in the epitaxial region is characterized by a leakage parameter a. Experimentally, for diodes with epitaxial film widths much less than a diffusion length, a "box" profile accurately describes the injected minority carriers in the n region. The current is found to increase with increased epitaxial width at a fixed bias. A general switching expression for epitaxial diodes is presented and the validity of the expression is shown experimentally. The experimental values of a, determined independently from the current-voltage and switching characteristics, are in good agreement and show that the leakage of the high-low junction is dominated by the recombination of minority carriers in the n-n⁺space-charge region.     

Tunneling recombination in silicon avalanche diodes

Distribution of the tunneling-recombination current over the space-charge region in a p-n junction was simulated mathematically. It is shown that the recombination rate saturates if the probability of tunneling is low. An expression for current-voltage characteristics of the p-n junction in the case of tunneling recombination is derived. The current-voltage characteristics of silicon avalanche diodes containing dislocations were studied experimentally. The results of numerical calculations based on the tunneling-recombination model are consistent with experimental data.     

Electrical characteristics of GaAs MIS Schottky diodes

The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of GaAs metal-insulator-semiconductor (MIS) Schottky barrier diodes are investigated over a wide temperature range and compared with MS diodes. The effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis. Excess currents observed at low forward and reverse bias have also been analyzed and their cause identified. A capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer, and a self-consistent model of the GaAs MIS Schottky barrier is developed by analyzing I-V and C-V data of both MIS and MS diodes.     

Gallium-Arsenide Point-Contact Diodes

This paper describes some of the work on gallium-arsenide point-contact diodes which is currently in progress at the Bell Telephone Laboratories, Holmdel, N. J. Gallium arsenide, one of the Group III-V intermetallic compounds, possesses properties which tend to make it superior to either silicon or germanium for many high-frequency diode applications. By controlling the resistivity of the gallium arsenide and the point-contact processing techniques, diodes have been fabricated specifically for use as millimeter wave first detectors, high-speed switches, and reactive elements for microwave parametric oscillators and amplifiers. The operating characteristics of several different types of gallium-arsenide reactive diodes are discussed and mention is made of simple design formulas which may be used to tentatively evaluate the performance to be expected from such diodes. Noise figure measurements are included in a resume covering some of the experimental results that have been obtained using gallium-arsenide point-contact diodes as variable reactance elements in microwave parametric amplifiers.     

Control of charge transport mode in the Schottky barrier by δ-doping: Calculation and experiment for Al/GaAs

The possibility of controlling the effective barrier height in Schottky diodes by introducing a δ-doped layer near the metal-semiconductor contact is considered. A decrease in the effective barrier height is caused by the increased role of carrier tunneling through the barrier. A complete quantum-mechanical numerical simulation of the effect of the δ-layer parameters (concentration and depth) on the current-voltage characteristics of modified diodes was carried out for the Schottky barrier contacts to n-GaAs. The simulation results were found to fit well the experimental characteristics of diodes produced by metal-organic chemical vapor epitaxy. The studies carried out made it possible to choose the optimal δ-layer parameters to produce low-barrier (about 0.2 eV) diodes with a reasonable nonideality factor (n≤1.5). Such structures can be employed to fabricate microwave detector diodes without bias.     

基于偏置马赫-曾德调制器的微波光子信号倍频

高速光信号源在现代光通信中不可或缺,目前倍受研究者关注。提出了利用一种具有偏置控制的马赫-曾德尔调制器(MZM),采用倍频方案产生高速微波光子信号,并进行了实验研究。通过在MZM 上施加一定的直流偏置引起两臂光脉冲的相位差,使光脉冲发生分裂实现倍频。实验中,利用5 GHz 的射频信号源,成功获得了频率增加一倍的10 GHz 高质量高速光信号。同时,也可以观察到在不同偏置电压下会产生不同的脉冲序列,发现优化偏压是实现高质量倍频的必要条件。该方案可用于产生40 GHz 以上的高频率光脉冲,可广泛应用于高速光通信。     

Observation of a peak in the negative-resistance/r.f.-voltage curve for high-low GaAs impatt diodes

We have observed experimentally a peak in the negative-resistance/r.f.-voltage curve in gallium-arsenide high-low impatt diodes for the first time. We have therefore tried to correlate this effect with the theory of the premature collection mode. This theory explained the high efficiency observed experimentally in GaAs impatt diodes with low-high-low structures in terms of a more favourable carrier transit angle accompanied by an increase of microwave output power at high r.f. voltages. This type of behaviour also occurs in the high-low high-efficiency GaAs impatts we have studied. Simultaneously, we performed a computer simulation on similar diodes, and these calculations confirm the observed peak and its dependance on the maximum efficiency and physical parameters.     

Gate formation in GaAs MESFET's using ion-beam etching technology

The use of ion-beam etching for the controllable formation of very thin active channel layers in GaAs MESFET's is investigated and compared with chemical and plasma etching techniques. The Schottky gate diodes associated with ion-beam etched surfaces show significant surface damage, a substantial part of which can be removed by annealing. Typical annealed diodes exhibit a barrier height of 0.53 eV and an ideality factor of 1.22. A modified Schottky theory is presented which includes the effects of surface damage and a thin interfacial layer between the metal and semiconductor. This model appears to account for most of the observed behavior. Capacitance-voltage-and current-voltage characteristics are presented for both large-area diodes on ion-beam etched surfaces and for MESFET's with gate lengths of 3 and 0.15 µm.     

Modeling the effect of deep traps on the capacitance–voltage characteristics of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates

Numerical simulation, using SILVACO-TCAD, is carried out to explain experimentally observed effects of different types of deep levels on the capacitance–voltage characteristics of p-type Si-doped GaAs Schottky diodes grown on high index GaAs substrates. Two diodes were grown on (311)A and (211)A oriented GaAs substrates using Molecular Beam Epitaxy (MBE). Although, deep levels were observed in both structures, the measured capacitance–voltage characteristics show a negative differential capacitance (NDC) for the (311)A diodes, while the (211)A devices display a usual behaviour. The NDC is related to the nature and spatial distribution of the deep levels, which are characterized by the Deep Level Transient Spectroscopy (DLTS) technique. In the (311)A structure only majority deep levels (hole traps) were observed while both majority and minority deep levels were present in the (211)A diodes. The simulation, which calculates the capacitance–voltage characteristics in the absence and presence of different types of deep levels, agrees well with the experimentally observed behaviour.     

Measurement and Characterization of Microwave Interaction between Integrated Distributed Feedback Laser Diode and Electro-Absorption Modulator

Integrated electro-absorption-modulated distributed feedback laser diodes (EMLs) are attracting much interest in optical communications for the advantages of a compact structure, low power consumption, and high-speed modulation. In integrated EML, the microwave interaction between the distributed feedback laser diode (DFB-LD) and the electro-absorption modulator (EAM) has a nonnegligible influence on the modulation performance, especially at the high-frequency region. In this paper, integrated EML was investigated as a three-port network with two electrical inputs and a single optical output, where the scattering matrix of the integrated device was theoretically deduced and experimentally measured. Based on the theoretical model and the measured data, the microwave equivalent circuit model of the integrated device was established, from which the microwave interaction between DFB-LD and EAM was successfully extracted. The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling. The electrical isolation is bidirectional while the optical coupling is directional, which aggravates the microwave interaction in the direction from DFB-LD to EAM.     

Analysis of GaAs tunnel diode oscillators

GaAs tunnel diode oscillators are analyzed using a tenth-order power series approximation of the current-voltage characteristics of the diodes. The analysis yields significantly better agreement between measured and calculated power outputs than previous analyses which were based on a cubic approximation of the current-voltage characteristics.     

Determination of the charge transport mechanism in <Emphasis Type="Italic">p-n</Emphasis> junctions by analyzing temperature dependences of forward current-voltage characteristics

A method is suggested for determining the charge transport mechanism in p-n junctions by analyzing the temperature dependence of forward current-voltage characteristics at a low injection level. The method has been experimentally tested with Si:Au diodes, green GaP LEDs, and blue AlGaN/InGaN/GaN LEDS with a quantum well.     

An analysis of the charge-transport mechanisms defining the reverse current-voltage characteristics of the metal-GaAs barriers

Reverse current-voltage characteristics of metal-GaAs contacts with a Schottky barrier were measured. Linear portions of the reverse-current dependence on the squared electric-field strength in the space-charge region of diodes were obtained. Such a dependence is related to electron interaction with the lattice vibrations. The reverse current of the Mo-GaAs:Si contacts is analyzed at different temperatures. Results of the analysis showed that measured current-voltage characteristics are controlled by the phonon-assisted electron tunneling from metal into semiconductor with the involvement of a deep center attributed to the EL2 trap. A similar mechanism governs the reverse current-voltage characteristics of the Ni-GaAs:S Schottky diodes.     

Microwave modulation of laser diodes with optical feedback

It is shown theoretically and experimentally that significant variations in the microwave modulation responses of laser diodes occur due to optical feedback from the transmission fiber. These variations decrease if the laser spectrum is less coherent; this can be achieved, for example, by increasing the intensity modulation index. In a recent letter the authors (1989) discussed the small-signal transfer functions; large deviations in the amplitude and the phase response resulted from optical feedback. For large-signal modulation, weaker feedback-induced deviations of the transfer function were predicted by W.I. Way and M.M. Choy (1988). The microwave modulation characteristics are considered in more detail, including the effects of higher modulation indexes. For a typical intensity modulation index of 26%, variations of up to 3 dB in amplitude and 60° in phase were observed     

Microwave-signal generation in a planar Gunn diode with radiation exposure taken into account

Microwave-signal generation in planar Gunn diodes with a two-dimensional electron gas, in which we previously studied steady-state electron transport, is theoretically studied. The applicability of a control electrode similar to a field-effect transistor gate to control the parameters of the output diode microwave signal is considered. The results of physical-topological modeling of semiconductor structures with different diode active-region structures, i.e., without a quantum well, with one and two quantum wells separated by a potential barrier, are compared. The calculated results are compared with our previous experimental data on recording Gunn generation in a Schottky-gate field-effect transistor. It is theoretically and experimentally shown that the power of the signal generated by the planar Gunn diode with a quantum well and a control electrode is sufficient to implement monolithic integrated circuits of different functionalities. It is theoretically and experimentally shown that the use of a control electrode on account of the introduction of corrective feedback allows a significant increase in the radiation resistance of a microwave generator with Schottky-gate field-effect transistors.     

Dependence of photoinduced changes in photovoltaic and dark electrical properties of hydrogenated amorphous silicon diodes on changes in the film properties of hydrogenated amorphous silicon

Computer simulation of hydrogenated amorphous silicon (a-Si:H) p-i-n type or n-i-p type diodes has been used to clarify the relationship between the photoinduced changes in photovoltaic and dark electrical properties of a-Si:H diodes and those in a-Si:H film properties. The origins of observed decrease in the short-circuit current and the fill factor are discussed referring to the decrease in carrier lifetimes, the change in electric field distribution in the undoped layer reflecting the increase in the density of ionized gap states, and the increase in interface recombination velcoity. Possible reasons for the observed differences in the photoinduced changes in photovoltaic properties between p-i-n type and n-i-p type a-Si:H diodes are also discussed. The observed changes in dark current-voltage characteristics of a-Si:H diodes can originate from the decrease in carrier lifetime. Some comments are also made on the "bulk or surface problem" of the photo-induced changes in a-Si:H p-i-n or n-i-p diodes.     

Characteristics of metal-insulator-metal diodes as generators offar-infrared radiation

Characteristics of metal-insulator-metal (MIM) diodes which are used as mixer-generators of far-infrared (FIR) radiation have been investigated for nine different diode base metals. It was found that a W-Fe diode works as effectively as a W-Co diode in generating tunable FIR radiation by mixing two CO₂ lasers and microwave radiation. The bias dependences of W-Ni, W-Co, and W-Fe MIM diodes have also been examined. Observed bias results can be predicted by analyzing their current-voltage characteristics     

High-Frequency Fiber Bragg Grating Sensing Interrogation System Using Sagnac-Loop-Based Microwave Photonic Filtering

A novel high-frequency fiber Bragg grating (FBG) sensing interrogation system by using fiber Sagnac-loop-based microwave photonic filtering is proposed and experimentally demonstrated. By adopting the microwave photonic filtering, the wavelength shift of sensing FBG can be converted into amplitude variation of the modulated electronic radio-frequency (RF) signal. In the experiment, the strain applied onto the sensing FBG has been demodulated by measuring the intensity of the recovered RF signal, and by modulating the RF signal with different frequencies, different interrogation sensitivities can be achieved.