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Impact ionization in GaAs-based planar Gunn diodes is studied through electroluminescence (EL) analysis with the aim of reducing its magnitude by means of contact design and shaping, and thus enhance device performance and reliability. Designs in which the diode ohmic anode has an overhanging Schottky extension (composite anode contact) are shown to result in a significantly reduced amount of impact ionization, as compared with a simple ohmic contact design. The EL results are consistent with Monte Carlo simulations, which show a reduced impact ionization in composite anode contact devices due to a reduced electron density beneath the anode Schottky extension that, on the one hand, weakens the Gunn domain electric field and softens its variations near the anode edge, and, on the other hand, reduces the number of electrons capable of generating holes by impact ionization. A comparison between standard and composite anode contact approaches in terms of radio-frequency operation of the devices is made showing oscillations up to 109 GHz with an output power of -5 dBm in devices featuring the composite anode contact and no oscillations from all-ohmic contact devices. The findings reported in this paper may be useful not only for the design and the fabrication of planar Gunn diodes but also for other devices such as high-electron-mobility transistors where impact ionization can result in reliability limitations. [ABSTRACT FROM AUTHOR]

An effect of the position of notch-doping layer in 1-μm GaN Gunn diode on threading dislocations (TDs) distribution is investigated by transmission electron microscopy. Compared with the top-notching-layer (TNL) structure, the bottom-notching-layer (BNL) structure can efficiently reduce the TDs density and improve the crystal quality in the transit region of GaN Gunn diode because it exhibits twice-transition of growth mode from atomic step flow to layer-by-layer nucleation and leads to a significant annihilation of TDs before penetrating into the transit region. X-ray diffraction and Raman spectroscopy reveal that the BNL structure has less compressive stress than the TNL structure. [ABSTRACT FROM AUTHOR]

Abstract: We present detailed design, fabrication and characterization of In0.23Ga0.77As-based planar Gunn diodes in this paper. The devices have AlGaAs/InGaAs/AlGaAs heterojunctions that were grown on a semi-insulating GaAs wafer using molecular beam epitaxy technology. Electron beam lithography was used to define anode and cathode terminal patterns. Devices with various anode–cathode separations (e.g. 4–1.4μm) were fabricated on the same chip. Spectrum measurements showed oscillation frequencies between 36GHz and 118GHz in the fundamental transit-time mode of operation. These devices show great potential as millimeter wave and sub-millimeter wave signal sources for their small size, MMIC compatibility and lithographically controlled oscillation frequencies. [Copyright &y& Elsevier]

This paper presents an improved negative differential mobility model for GaN and AlGaN to simulate GaN Gunn diodes at terahertz frequencies. Temperature-dependent parameters \nusat, Ec, \alpha, \delta, and \gamma are proposed to improve the accuracy of the mobility model at high temperatures. In particular, an Al-composition-related coefficient fZ(x) and a random-alloy-potential-related factor falloy(p) are developed for an AlGaN mobility model. Simulation results show that notched doping GaN and AlGaN/GaN heterostructure Gunn diodes, both including 0.6-\mu\m transit and 0.2-\mu\m electron launching regions, have the capability of generating fundamental frequencies of 352–508 and 332–469 GHz, respectively, with a maximum radio-frequency (RF) power density of \sim \10^10\ \W/cm^3 and RF efficiency of over 2% accompanied with a shift of an oscillation mode from a dipole-domain mode toward an accumulation mode as the temperature rises from 300 to 500 K. [ABSTRACT FROM AUTHOR]

Based on the substrate integrated waveguide (SIW) technology, a novel W-band low phase noise GaAs Gunn planar harmonic oscillator is developed in this paper. The technique of harmonic extraction from Gunn diodes and SIW resonant cavity structures are discussed in detail. Due to the high quality factor and planar structure of the SIW cavity resonator, the oscillator is characterized by some advantages such as low phase noise, small size, low cost and planar integration. The measured phase noise is −108.56 dBc/Hz at 1 MHz offset and the output power is more than 9 dBm at 94.78 GHz. A 300 MHz of linear tuning range with power fluctuation less than 1.5 dB is observed when the Gunn diode is biased from 4 to 5.3 V. [ABSTRACT FROM AUTHOR]

A drastic reduction in the residual voltage (from ~100 V to a few volts) and a significant (factor of ~2) increase in the dU / dt switching rate is demonstrated experimentally in the superfast (~200 ps) avalanche switching of a GaAs bipolar junction transistor with increased emitter area. This result is not a trivial one as only a small number of conductive channels of a few micrometers in diameter participate in the transient independently of the emitter size, while the remaining (passive) part of the structure supplies the switching channels with the currents circulating inside the chip, which makes the impact ionization in the filaments even more powerful. Excellent agreement was found between the experiment and a "two-transistor" model specially developed here, with one transistor simulating the switching channels and the other the nonswitched part of the structure. Much higher switching stability and reproducibility and much lower power dissipation were observed in the structure with increased emitter area. [ABSTRACT FROM AUTHOR]

In this paper, we report on the bias oscillation of GaN-based Gunn diodes realized on a n+-GaN substrate. Different contact materials, ambient gases, and pulsewidths were used and compared with regard to device stability. A wide negative-differential-resistance (NDR) region was measured for electrical-field values E larger than a threshold field Eth of 150 kV/cm. Electrical fields much higher than the threshold value did not lead to any electromigration effects or discharging problems from the contacts. The drift velocity derived from the current-voltage characteristics, diode geometry, and doping concentration in the active layer was estimated to be 1.9 x 107 cm/s. Bias oscillations were obtained for the GaN Gunn diodes in the presence of a series inductance. [ABSTRACT FROM AUTHOR]

Design of tunable Gunn diode—based active antenna module including a new type of planar dielectric resonator (PDR) tuned by a ferroelectric (FE) varactor is presented. The module is designed in such a way that the PDR acts both as a stabilizing resonator and as a radiator. MW properties of FE elements used for VCO tuning are considered. The module operates at frequency around of 17 GHz and demonstrates the radiated power of 8.8 ± 0.1 dBm over the 130 MHz tuning range and a phase-noise level of -95 dBc/Hz at 100 kHz offset. 65° width of the radiation pattern in both the E and H planes corresponding to a gain of 5.1 dBi was measured. The maximal VCO power limited by the dielectric nonlinearity of a FE film in the microwave electric field and by the FE film overheating is estimated for FE film-based varactors of the planar and parallel structures. [ABSTRACT FROM AUTHOR]

Design of tunable Gunn diode-based active antenna module including a new type of planar dielectric resonator (PDR) tuned by a ferroelectric (FE) varactor is presented. The module is designed in such a way that the PDR acts both as a stabilizing resonator and as a radiator. Microwave properties of FE elements used for voltage-controlled oscillator (VCO) tuning are considered. The module operates at a frequency around of 17 GHz and demonstrates the radiated power of 8.8±0.1 dBm over the 130-MHz tuning range and a phase-noise level of -80 dBcIHz at 100-kHz offset. 65° width of the radiation pattern in both the E- and H-planes corresponding to a gain of 5.1 dBi was measured. The VCO module has been tested in the regime of the frequency modulation. The output signal spectra measured and simulated for modulating bipolar voltage pulses of repetition frequency f = 2MHz are presented. [ABSTRACT FROM AUTHOR]

This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap AlxGa1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced. [ABSTRACT FROM AUTHOR]

A 60-GHz frequency-stabilized small oscillator consisting of a Gunn diode, a circulator, and a matched termination is fabricated by using NRD guides. The emphasis in this paper is adaptability to a rectangular waveguide circuit. To this end, an NRD guide–waveguide transition is designed. In the 60-GHz NRD Gunn diode oscillators to date, Gunn diodes sealed in a package dedicated to the NRD guide have been placed on special order. With a view to cost reduction, a Gunn diode mount is conceived in which a general-purpose-type Gunn diode can be used. The oscillation output of the fabricated oscillator is 13 dBm and the phase noise at 300 kHz offset is -113 dBc/Hz. Further, the frequency variation due to ambient temperature change is -1.3 ppm/°C so that the fabricated millimeter-wave oscillator is highly stable, with medium power output and low noise. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(3): 26–32, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20290 [ABSTRACT FROM AUTHOR]

A microwave cavity, the loaded Q of which is improved by mounting the Gunn diode outside the resonant cavity, is described. The enhanced characteristics of the oscillators and amplifiers using this cavity as an oscillatory system are presented. [ABSTRACT FROM AUTHOR]

The n+-n-n+-n++-GaAs epitaxial structures were MBE-grown on porous nanostructured and traditional (standard) heavily doped n++-GaAs substrates. On their basis, we fabricated the Gunn diodes generating power output in the 44—59 GHz (first harmonic) and 101—104 GHz (second harmonic) frequency ranges. For both harmonics, the power output of the Gunn diodes grown on porous substrates was shown to be from 20 to 30% higher than those grown on the flat ones. [ABSTRACT FROM AUTHOR]

A new method for determining the bulk lifetime of minority carriers in single-crystal silicon ingots is proposed. A photoconductivity signal measured at a microwave frequency and normalized to its initial value is compared with the results of calculating the total number of excess charge carriers N(t)/Nst, where Nst corresponds to the quasi-steady-state photoconductance. The location of the point of intersection of the photoconductivity-relaxation curve and the dependence N(t=τ)/Nst determines the bulk lifetime τ = τv . The measurements were performed on silicon ingots with different resistivities grown by crucibleless zone melting and the Czochralski method. The experimental data obtained agree well with the results of calculation. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The analysis methods for the steady-state responses of the mm-wave band NRD-guide negative impedance oscillators based on nonlinear microwave autonomous circuits harmonic balanced method are presented in the paper in details. Firstly, the large-signal nonlinear lumped equivalent circuits of the Gunn diode are studied in mm-wave bands. Then, the performances of two kinds of NRD-guide autonomous circuits, the probe-exciting LSM11o-mode oscillator and the LSE11o-mode oscillator, are analyzed by the way of extracting the large-signal dynamic harmonic admittance (conductance) of the Gunn diode or directly configuring the harmonic balance equations for the oscillator. The input impedance of the exciting probe in the oscillator and the performances of the load-pulling and the local stability of the NRD-guide oscillator are also involved. [ABSTRACT FROM AUTHOR]

Solid-state THz devices usually suffer from low power output. This, however, can be overcome by efficient power combining. In this paper, the power combining of a chain of active devices (longitudinal array of N Gunn diodes) in a semi-infinite transmission line has been simulated. Superlinear growth of power P is found in a line with inductive-capacitive elements: P is quadratic in N when P is small and becomes linear when P is large. Intricate auto-modulation due to coupling between the devices is shown to accompany power combining. [ABSTRACT FROM AUTHOR]

Phase, structural, and electrical properties of Au–Mo–TiB[sub x]–AuGe–GaAs multilayer contact systems, which are used in the process of formation of GaAs-based Gunn diodes, were investigated. The phase composition and level of residual stresses were investigated by X-ray diffraction, the morphological specific features of Au films were investigated by the AFM method, and current–voltage characteristics were investigated in the region of a weak electric field. The investigations were carried out prior to and after rapid thermal annealing in hydrogen at T = 400, 600, and 800°C for 60 s. It is shown that right up to the annealing temperature T = 600°C, the buffer properties of TiB[sub x] are retained. The role of internal mechanical stresses in the degradation of nonrectifying Au–Mo–TiB[sub x]–AuGe–GaAs contacts is established. © 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Continuous electromagnetic emission from a Gunn diode built in a microstrip log-periodic antenna in the frequency range from 25 to 60 GHz is studied experimentally. The microstrip antenna was located on an insulating substrate with a thickness of about a quarter of the wavelength and with a metallized back side. It is shown that the output radiation power of such an antenna reaches 5 mW, which is over 50% of the power received from similar diodes in the waveguide cavity. The oscillation regime was varied from single-mode to noise-like, depending on the dielectric thickness and could be synchronized by external emission. Such a quasi-optical structure based on a Gunn diode is convenient for summing up powers from individual oscillators in an open resonator and is of great interest for the terahertz frequency band. [ABSTRACT FROM AUTHOR]

An open resonator with its constituent the barrelshaped reflected surface is described. Millimeter wave-band oscillator and amplifier based on this resonator investigated. The power and frequency characteristics are presented. It is shown that this device can best be used as a regenerative amplifier. [ABSTRACT FROM AUTHOR]

A two-temperature model of intervalley electron transfer in the variband semiconductor is developed. This model was applied to examine the operation of the Gunn diodes based on the variband Inx(z)Ga1-x(z)As. In the active diode region the semiconductor composition x(z) is linearly coordinate-dependent. It is shown that operation of the diode with a variband active region is determined by the coordinate dependency of relaxation frequency of electron concentration in the τ-valley of Inx(z)Ga1-x(z)As. If this frequency is a decreasing function of coordinate (in the Inx(Z)Ga1-x(z)As this occurs when x(z) increases) the dipole domains propagate in the diode, while the opposite case is featured by the propagation of charged layers. The maximum output power flux ∼6.5 kW/cm2 was obtained for the GaAs-In0.4Ga0.6As - diode at a frequency of 37 GHz with a 12% efficiency. [ABSTRACT FROM AUTHOR]

The operation of Gunn diode with series concatenated InP0.7As0.3 and Ino0.4Ga0.6As active regions was analyzed in terms of the two-temperature intervalley electron transfer model. The energy and frequency characteristics of the diodes differing in the type of cathode metallic contact were obtained (barrier height is 0.04 eV). The output characteristics of the diode with two active regions and a blocking metallic cathode were found to result from the complex interplay between the physical processes occurring simultaneously in the two regions. The highest output power flux was estimated to be ∼40 kW/cm2 at a frequency of 42 GHz and a generation efficiency ∼20%. The diode with an antiblocking metallic cathode contact operates as a heterocathode diode, i.e. a generation of current oscillations is provided exclusively by the ln0.4Ga0.6As active region. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental research of quasi-optical solid-state oscillators (SSO) with 8-millimeter (8-mm) band Gunn diodes using a stabilizing ellipsotoric open resonator (ETOR). The prospect of applying such devices for improving the output parameters of solid-state sources of radiation within the millimeter-wave bandwidth has been demonstrated. [ABSTRACT FROM AUTHOR]

A low-cost, high-performance X-band Gunn diode oscillator for educational and research purposes has been developed. The cavities have been manufactured on a standard WR90 rectangular waveguide with UBR100 flange in order to make it compatible with the waveguide circuitry usually available in a basic microwave laboratory. The capability of sweeping the whole X band at constant output power and low phase noise, as well as the low cost of its components, make this device suitable for users at any level. As an example of its many educational applications, a multiple frequency continuous-wave (MFCW) radar has been developed, and the results of the laboratory implementation are shown. [ABSTRACT FROM AUTHOR]

The operation of n+-D- n+ Gunn diode with a dielectric based on wide-gap Al0.2Ga0.8As semiconductor was examined. The model is suggested allowing the diode oscillation mode to be analyzed. The peculiarities of electron transfer and current instability are scrutinized. The energy characteristics of diode operation in the centimeter range are estimated. The perspectives of diode use are outlined. [ABSTRACT FROM AUTHOR]

The operation of a series-connected resonant-tunnel diode and Gunn diode in the resonance circuit is considered. The current-voltage characteristics of diode combination have the peculiarities which lead to a current jump as the voltage increases or decreases at the diodes. The peculiarities of the current-voltage characteristics and current jump are analyzed for the different lengths of the Gunn diodes which determine the current waveform of the diodes in the resonance circuit. It is shown that the oscillation can occurs in the millimeter wave band at the certain ratios of the parameters of resonant-tunnel and Gunn diodes due to the resonance tunneling and intervalley electron transfer. When joint operation of such diodes there are two generation regions: at the sacrifice of the resonance tunneling and intervalley electron transfer. In these regions the generation is possible at multiple frequencies. [ABSTRACT FROM AUTHOR]

The 1961 Sah equivalent circuit model is extended to hydrodynamic transport in semiconductors for applications to high speed one-carrier devices such as the Gunn diodes. A transient simulation of the Gunn diode is given using the circuit simulator SPICE3 to demonstrate this hydrodynamic extension. [Copyright &y& Elsevier]

The operation of the In0.4Ga0.6As Gunn-effect diodes with a m-n: InP1-xAsx cathode has been investigated in terms of a two-temperature model at a crystal lattice temperature of 300K. and an active region length of 0.5; 0.8; 1.0 μ m. The optimal InP1-xAsx, composition is determined for each diode length. For the diode having a 10 μm-active region an optimal height of the potential barrier on the metal-semiconductor contact is likewise specified. It is shown that the maximum generation frequency is ∼250GHz. [ABSTRACT FROM AUTHOR]

Examines the W-band overmoded-waveguide oscillator with Gunn diodes. Output power and efficiency of gunn diodes contained in the waveguide array; Improvement on the efficiency of the gunn diodes using a small resonator; Conversion on the output mode of fundamental-mode waveguides.

The negative-differential-drift-velocity instability, which forms the basis of Gunn high-frequency generators, can originate from Ridley-Watkins-Hilsum or negative effective mass (NEM) mechanisms. The first mechanism is dissipative by nature. The second is mainly drift-related. Therefore, the second mechanism promises to be more effective. We show the existence of stationary oscillatory regimes in the ballistic NEM p+ p p+-diodes, which have a base in the form of a periodic system of parallel p-type quantum-well channels with base length up to 30 nm. An oscillation frequency, which depends on the base length, doping, and spatial period, as well as loads and voltage across the diode, ranges from 1 to 5 THz. We propose an additional combined quantum GaAs-AlGaAs-heterostructure, which can be overgrown on a cleaved edge of a specially grown wafer. This structure is intended to obtain electron dispersion relations with NEM sections in the useful energy range of 0.1-0.25 eV [ABSTRACT FROM PUBLISHER]

Temporal parameters of the current pulses generated by a Gunn diode operating in domain mode in relation to the supply voltage and load resistance are numerically simulated. The results of the numerical and analytical studies are compared. The validity range of the analytical formulas is ascertained in detail. In the context of the considered model, the minimum pulse duration and the time of domain formation are obtained at zero load and for a supply voltage exceeding the critical value by a factor of 1.25. [ABSTRACT FROM AUTHOR]

Discusses the improved heat dissipation of InP Gunn devices. Radio frequency power levels and oscillation frequencies resulting from the improved heat dissipation; Corresponding direct current-to-radio frequency conversion efficiencies; Properties of millimeter-wave devices.

Planar Indium Gallium Arsenide (In 0.57 Ga 0.47 As) Gunn diode was fabricated on a semi-insulating indium phosphide substrate with on chip matching circuit to enable the extraction of second harmonic in millimeter and terahertz frequencies. The In 0.57 Ga 0.47 As planar Gunn diodes were designed with an active length of 4 μm, channel width of 120 μm and integrated with a novel diamond resonator to suppress the fundamental and extract the second harmonic. The experimental results gave good fundamental suppression and extraction of second harmonic (121.68 GHz) with an RF output power of −14.1 dBm. This is highest recorded power at the second harmonic from a planar Gunn diode. [ABSTRACT FROM AUTHOR]

Examines the application of a Gunn-diode (GD) current-pulse generator for modulation of semiconductor lasers. Current characteristics of the GD and the injection lasers; Electric domains of a GD; Ranges of maximum power and radiation wavelengths.

Describes a second-harmonic Gunn diode oscillator with a rectangular waveguide resonator for the fundamental frequency. Results of testing in a 50 gigahertz frequency range; Frequency decrease when a static magnetic field is applied.

The paper deals with some special features of Gunn diode operation in a resonant circuit, which arise from the non-linear characteristics of the diode's complex impedance. Autonomous and non-autonomous modes of operation for Gunn diode oscillators are discussed. Thc considerable influence that the non-linearity of the Gunn diode's domain capacitance has on the operation of such systems is shown. Parametric phenomena caused by this non-linearity are examined. The method used allows a complete study of such systems by comparatively simple but correct treatment of the problems. The results obtained can be successfully used in the study of resonant circuits with microwave transistors, IMPATT diodes and Josephson junctions. All the results are experimentally proved. [ABSTRACT FROM AUTHOR]

The negative conductance of X-band GaAs Gunn diodes, as a function of microwave voltage amplitude across the diodes, has been studied under different circuit conditions and bias voltages giving rise to a frequency variation from 8·2 to 13·1 GHz. Negative conductance has been found to increase near the transit-time frequency (1⁄t × 10[sup +7]) and falls off rapidly at higher as well as lower frequencies. Also the device D15 shows a peculiar behaviour in that its build-up time is very small when oscillating at frequencies higher than transit time frequency. A frequency shift has been observed with the variation of diode position in the cavity. [ABSTRACT FROM AUTHOR]

A Varian Q-band E-110 microwave bridge for electron paramagnetic resonance (EPR) spectroscopy has been modified by addition of a low-phase noise Gunn diode oscillator of our own design, a low-noise GaAs field-effect transistor microwave signal amplifier, and a balanced mixer requiring high input power (10 mW) at the local oscillator port. The oscillator has previously been found to have -129 dBc/Hz phase noise, 22 dB lower than for the original klystron. Noise measurements indicate that the microwave amplifier and mixer reduce the overall receiver noise figure by 24.6 dB, a very significant improvement. It is shown that reduction of both phase noise and receiver noise are required in order to achieve full improvement in signal-to-noise ratio over the full range of available microwave power. Spectra of 1.6 × 10[sup -6] M [sup 15]N-perdeutero TEMPONE (1-oxyl-2,2,6,6-tetramethyl-4-piperidone) and of 10[sup -6] M Mn[sup 2+] are shown in order to demonstrate sensitivity. [ABSTRACT FROM AUTHOR]

The performance characteristics of a 35-GHz cavity stabilized Gunn diode oscillator is presented. The frequency variations are found to be reduced by a factor of 66 when the oscillator is locked to the cavity. [ABSTRACT FROM AUTHOR]

A technique for obtaining multidomain operation of Gunn diodes is proposed. Device impedance is increased, leading to large potential increases in output power. The precision required of the doping profile has been estimated by simulation and appears to be within the capabilities of molecular beam epitaxy. Estimates of output power, taking thermal effects into account, indicate that in many cases on N-domain diode can produce N2 times as much power as a single-domain diode. For example, it should he possible to obtain 1.8 W from a three-domain device oscillating at 30 GHz. [ABSTRACT FROM AUTHOR]

Focuses on the development of a millimeter-wave oscillator which incorporates an overmoded-waveguide resonator with an array of fundamental-mode waveguides containing Gunn Diodes. Use of mode conversion of radiation power from Gunn diodes in the waveguide array; Configuration of an overmoded-waveguide oscillator with diode devices.

Presents a cavity-backed, Gunn-diode-driven, self-mixing active inverted stripline circular patch antenna. Active antenna configuration; Evaluation of the performance of the active antenna; Evaluation of the varactor-tuning capabilities of the device.

Planar Indium Gallium Arsenide (InGaAs) Gunn diodes with on chip matching circuits have been fabricated on a semi-insulating Indium Phosphide (InP) substrate to enable the extraction of the second harmonic in millimeter-wave and terahertz frequencies. The planar Gunn diodes were designed in coplanar waveguide (CPW) format with an active channel length of 4 μm and width 120 μm integrated to CPW matching circuit and radial stub resonator to suppress the fundamental and to extract the second harmonic. The initial experimental measurements have given a second harmonic signal at 118 GHz with an output power of -20 dBm and the fundamental signal at 59 GHz was suppressed to the noise level of the experimental set-up. [ABSTRACT FROM AUTHOR]

Experiments are reported which indicate that simultaneous oscillations at two frequencies may be generated in a Gunn diode oscillator. The lower frequency is within the range 18-044 GHz, while the higher frequency lies between 18 and 375 GHz, the transit-time frequency being 18 GHz. The two frequencies may be individually changed without affecting each other. [ABSTRACT FROM AUTHOR]

The characteristics of detected wave form, and output power of the oscillations of a Gunn diode, with an oscillation frequency of approximately 4 GHz mounted inside a coaxial type resonant cavity, at varied cavity lengths, were measured when the temperature was lowered from room temperature to -120degreesc.
Heat is generated when a Gunn diode is operated at relatively high output power. Generally, because of this heat, the quality characteristics of the diode get worse. That is why that the characteristics of the Gunn diode at higher temperatures, above room temperature, has practical importance and a relatively large amount of research has been done on it. On the other hand, we know that theoretically the output power and efficiency of oscillation in the diode increases gradually as the temperature decreases from room temperature. As far as we know, there are no reports or papers published concerning the low temperature characteristics of the Gunn diode. [ABSTRACT FROM AUTHOR]

A consistent derivation of the small-signal equivalent circuit is given for a Gunn diode while being traversed by a steady-state high field domain. The result of Hobson is confirmed, but with a somewhat different meaning of the domain negative conductance and of the domain capacitance. Application is made to parametric amplification and to Thim's travelling domain amplifier. [ABSTRACT FROM AUTHOR]