Gunn Diode Research Articles

W-band 도파관 FTO 적용을 위한 전류제한 InP Gunn diode 설계 및 제작

W-band 도파관 FTO 적용을 위한 전류제한 InP Gunn diode 설계 및 제작

Terahertz oscillations in an In0.53Ga0.47As submicron planar Gunn diode

The length of the transit region of a Gunn diode determines the natural frequency at which it operates in fundamental mode—the shorter the device, the higher the frequency of operation. The long-held view on Gunn diode design is that for a functioning device the minimum length of the transit region is about 1.5 μm, limiting the devices to fundamental mode operation at frequencies of roughly 60 GHz. Study of these devices by more advanced Monte Carlo techniques that simulate the ballistic transport and electron-phonon interactions that govern device behaviour, offers a new lower bound of 0.5 μm, which is already being approached by the experimental evidence that has shown planar and vertical devices exhibiting Gunn operation at 600 nm and 700 nm, respectively. The paper presents results of the first ever THz submicron planar Gunn diode fabricated in In0.53Ga0.47As on an InP substrate, operating at a fundamental frequency above 300 GHz. Experimentally measured rf power of 28 μW was obtained from a 600 nm long × 120 μm wide device. At this new length, operation in fundamental mode at much higher frequencies becomes possible—the Monte Carlo model used predicts power output at frequencies over 300 GHz.

Experimental Study of Frequency Multiplication in a Distributed Array of SIS Junctions

We report the first experimental off-chip detection of frequency multiplication in a distributed array of superconductor-insulator-superconductor (SIS) junctions. A test device consisting of series array of 68 Nb/Al-AlOx/Nb tunnel junctions was designed to study generation of the second harmonic in the 190-210 GHz band. The SIS array was exited with microwave radiation at 3-mm band using a quasi-optically coupled Gunn oscillator, and the output response of the device was studied using a double-sideband SIS mixer operating in the 163-211 GHz range with 4-8 GHz IF bandwidth. We measured extremely sharp spectral signals, associated with the ×2 frequency multiplication by the SIS array. Single- and multi-photon processes were observed in the response of SIS tunnel junction-array to the applied microwave radiation, confirming device operation in the quantum mode. The output power of the multiplied signal increases linearly with the power of the pumping signal up to certain level and them saturates. In attempt to verify that the device produces noticeable power, the output of the test device was connected to the LO port of the SIS mixer, and an increase of 10%-20% in the SIS mixer dark current was observed. Further development of the demonstrated principle of frequency multiplication may lead to a practical frequency multiplier device.

Optimized V-shape design of GaN nanodiodes for the generation of Gunn oscillations

In this work, recent advances in the design of GaN planar Gunn diodes with asymmetric shape, so-called self-switching diodes, are presented. A particular geometry for the nanodiode is proposed, referred as V-shape, where the width of the channel is intentionally increased as approaching the anode. This design, which reduces the effect of the surface-charges at the anode side, is the most favourable one for the onset of Gunn oscillations, which emerge at lower current levels and with lower threshold voltages as compared to the standard square geometry, thus enhancing the power efficiency of the self-switching diode as sub-millimeter wave emitters.

Comparative Monte Carlo analysis of InP- and GaN-based Gunn diodes

In this work, we report on Monte Carlo simulations to study the capability to generate Gunn oscillations of diodes based on InP and GaN with around 1 μm active region length. We compare the power spectral density of current sequences in diodes with and without notch for different lengths and two doping profiles. It is found that InP structures provide 400 GHz current oscillations for the fundamental harmonic in structures without notch and around 140 GHz in notched diodes. On the other hand, GaN diodes can operate up to 300 GHz for the fundamental harmonic, and when the notch is effective, a larger number of harmonics, reaching the Terahertz range, with higher spectral purity than in InP diodes are generated. Therefore, GaN-based diodes offer a high power alternative for sub-millimeter wave Gunn oscillations.

Computer‐aided design of millimeter‐wave continuous wave power combiner

ABSTRACTA two‐diode injection locked power combiner has been designed with computer‐aided design approach and experimentally tested. An output power of 25.48 dBm with a phase noise of −100 dBc/Hz for a frequency offset of 10 kHz from the carrier frequency of 34.6 GHz has been achieved. The power‐combiner cavity has been simulated with 3D full wave electromagnetic field simulator HFSS and cosimulated with the equivalent circuit of the continuous wave Gunn diode using ANSYS Designer. The experimental result closely matches with the simulation and is better than the analytical approach reported by earlier researchers. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:705–709, 2014

TIME-DOMAIN SIMULATION OF POWER COMBINING BY A PARALLEL CONNECTION OF STRIP LINES WITH GUNN DIODES

In radio engineering, the development of compact, high-power radiation sources is impossible without power of individual sources being combined. The GaN Gunn diodes show a good potential for this application. The calculus of systems, requiring power combination, particularly in the time-delay problems, is handicapped by a lack of analysis and computation techniques, despite all evident advances. In this paper, we apply a new approach and our modification of the numerical Dormand-Prince method to perform time-domain calculation for a non-linear power combination in an active structure formed by a parallel connection between extended sections of strip lines and the Gunn diodes, characterized by a substantial feedback time delay. We have observed and explored complex dependences of the output power and oscillation period on the structure parameters. The results confirm the pronounced non-linear nature of the processes, and furnish an explanation to some real-life effects. The efficiency of the model was tested while analyzing an ultra-wideband field dynamics in a highly non-linear structures with a time delay, taking into account the delayed feedback of active devices toward external inputs. It was proven that simplified models are unsuitable for describing oscillations in non-linear, multicomponent active structures with a time delay, which require a direct time-domain calculation.

Monte Carlo simulation of THz frequency Gunn effect in GaAs MOSFET with excess of electrons in channel at impact ionization conditions

The results of Monte Carlo simulation of GaAs MOSFETs under impact ionization conditions in the conduction channel are presented. The main attention is paid to the transistor operation at a positive gate bias when the electron concentration in the channel under the gate considerably exceeds the channel doping level. The stationary characteristics including current voltage relation and velocity, energy and field profiles in the channel are calculated. Also, the drain current noise spectra at various drain biases are presented. The Gunn-effect dynamics in excess of electrons in the channel is investigated. The optimization of transistor geometrical, doping, and biasing parameters for high frequency generation is performed. It is shown that GaAs MOSFET can generate at 325 GHz frequency.

Monte Carlo simulation of THz frequency Gunn effect in GaAs MOSFET with excess of electrons in channel at impact ionization conditions

The results of Monte Carlo simulation of GaAs MOSFETs under impact ionization conditions in the conduction channel are presented. The main attention is paid to the transistor operation at a positive gate bias when the electron concentration in the channel under the gate considerably exceeds the channel doping level. The stationary characteristics including current voltage relation and velocity, energy and field profiles in the channel are calculated. Also, the drain current noise spectra at various drain biases are presented. The Gunn-effect dynamics in excess of electrons in the channel is investigated. The optimization of transistor geometrical, doping, and biasing parameters for high frequency generation is performed. It is shown that GaAs MOSFET can generate at 325 GHz frequency.

SIGNAL AND FLUCTUATION CHARACTERISTICS OF AUTODYNE VIBRATION AND DISPLACEMENT METERS

The research data and experimental results of particularities of formation of signal and noise characteristics of autodyne vibration and displacement meters functioning under the conditions of strong external feedback are provided for various operation points and methods for autodyne signal registration. The experimental results are obtained using the Tigel-08M hybrid integral module manufactured on the basis of 8-mm planar Gunn diode.

Measurement of the mobility and concentration of charge carriers in a Gunn gallium-arsenide diode using a near-field microwave microscope

The results of local contactless measurement of the dependence of conductivity in a Gunn diode on the external electrical bias are presented. The technique of local determination of the charge-carrier concentration and mobility in a commercially produced chip Gunn diode for various values of the supply voltage is proposed.

Investigation of the charge carrier concentration and electric field distribution in gallium arsenide Gunn diode

Numerical calculation of the stationary distribution of electric field and charge carrier concentration in Gunn diode has been performed for the one-dimensional case. In addition, experimental investigations of the specified characteristics were also carried out by using a near-field microwave microscope. Taking into account the dependence of the majority carrier diffusion coefficient on the electric field intensity was shown to be of crucial importance in describing the processes occurring in Gunn diodes. The numerical results were in good agreement with the results of conducted experiment.

EFFECTS OF UNILATERAL COUPLING BETWEEN TWO CHAOTIC X-BAND GUNN OSCILLATORS

Two X-band microwave Gunn oscillators have been separately operated with "below threshold" dc bias voltages under the influence of an injected weak RF field in their respective cavities to generate chaotic oscillations. The output of one such chaotic Gunn oscillator is injected into the other through a controllable coupling network to explore the possibility of synchronization between two oscillators. We establish through numerical simulation that (i) two oscillators with identical design parameters attain a state of complete synchronization and (ii) two oscillators with slightly different design parameters attain a state of generalized synchronization for reasonable value of coupling strengths. The occurrence of generalized synchronization has been proved through the "auxiliary" slave system approach of nonlinear analysis. Results of hardware experiments are incorporated to qualitatively support the observations made through numerical simulation.

Amplification of microwave oscillations on harmonics of the Gunn diode conductivity

The results of studying microwave amplifiers on the second harmonic of the negative conductivity of Gunn diodes operating in the centimeter waveband are presented.

The effect of phase stabilization of microwave oscillations in nanosecond Gunn oscillators

The effect of the semiconductor structure of an oscillator diode on the phase stabilization of microwave oscillations in a nanosecond Gunn oscillator by using a modulating voltage pulse edge is investigated. Numerical simulation is employed to determine phase deviations depending on the scatter of pulseedge duration and pulse amplitude. The standard deviation of phase-delay time of microwave oscillations in the oscillator with regard to a constant level at the modulating pulse edge and the standard deviation of phase difference of microwave oscillations in two electrodynamically insulated oscillators connected in parallel to one and the same modulator have been measured.

A study of the Gunn oscillator in deterministic and chaotic modes

Results of the experimental study of the Gunn oscillator in the deterministic and chaotic modes are presented. The design philosophy of the studied oscillator and method of its changing to the dynamic chaotic state are described.

InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner

We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/√Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated.

Backgating effect in III–V MESFET’s: A physical model

The backgating (sidegating) effect in III–V MESFET’s devices is analyzed through the modelisation of a Metal (Schottky barrier)–N (channel)–SI (Semi Insulating)–N+ (back-gate contact) structure. Numerical and analytical results, using the drift–diffusion charge transport model, show that along the applied voltage range associated with backgating: (i) quasi space charge neutrality across most of the bulk SI layer and (ii) quasi Boltzmann equilibrium for the free electron across the reverse biased N (channel)–SI contact prevail for GaAs (SI) or InP (SI). The circumstances under which a negative bias applied on the back-gate (N+) contact will either develop across the reverse biased N–SI contact (strong backgating) or across the SI layer (negligible backgating) are described by means of a simple analytical relation as a function of the deep level parameters values. The electric field dependence of the carrier mobility (Gunn effect) produces a backgating effect with a threshold voltage. The presence of a low lifetime, buffer layer, at the N–SI interface is shown to strongly reduce it.

Dislocation blocking by AlGaN hot electron injecting layer in the epitaxial growth of GaN terahertz Gunn diode

This paper reports an efficient method to improve the crystal quality of GaN Gunn diode with AlGaN hot electron injecting layer (HEI). An evident reduction of screw dislocation and edge dislocation densities is achieved by the strain management and the enhanced lateral growth in high temperature grown AlGaN HEI layer. Compared with the top hot electron injecting layer (THEI) structure, the bottom hot electron injecting layer (BHEI) structure enhances the crystal quality of transit region due to the growth sequence modulation of HEI layer. A high Hall mobility of 2934 cm2/Vs at 77 K, a nearly flat downtrend of Hall mobility at the temperature ranging from 300 to 573 K, a low intensity of ratio of yellow luminescence band to band edge emission, a narrow band edge emission line-width, and a smooth surface morphology are observed for the BHEI structural epitaxy of Gunn diode, which indicates that AlGaN BHEI structure is a promising candidate for fabrication of GaN Gunn diodes in terahertz regime.

Hot Brownian carriers in the Langevin picture: Application to a simple model for the Gunn effect in GaAs

We consider a charged Brownian gas under the influence of external, static and uniform electric and magnetic fields, immersed in a uniform bath temperature. We obtain the solution for the associated Langevin equation, and thereafter the evolution of the nonequilibrium temperature towards a nonequilibrium (hot) steady state. We apply our results to a simple yet relevant Brownian model for carrier transport in GaAs. We obtain a negative differential conductivity regime (Gunn effect) and discuss and compare our results with the experimental results.