Gunn Diode Research Articles

An empirical determination of upper operational frequency limits of transferred electron mechanism in bulk GaAs and GaN through ensemble Monte Carlo particle simulations

The ensemble Monte Carlo particle simulation technique is used to determine the upper operational frequency limit of the transferred electron mechanism in bulk GaAs and GaN empirically. This mechanism manifests as a decrease in the average velocity of the electrons in the bulk material with an increase in the electric field bias, which yields the characteristic negative slope in the velocity–field curves of these materials. A novel approach is proposed whereby the hysteresis in the simulated dynamic, high-frequency velocity–field curves is exploited. The upper operational frequency limit supported by the material is defined as that frequency, where the average gradient of the dynamic characteristic curve over a radio frequency cycle approaches zero. Effects of temperature and doping level on the operational frequency limit are reported. The frequency limit thus obtained is also useful to predict the highest fundamental frequency of operation of transferred electron devices, such as Gunn diodes, which are based on materials that support the transferred electron mechanism. Based on the method presented here, the upper operational frequency limits of the transferred electron mechanism in bulk GaAs and GaN are 80 and 255 GHz, respectively, at typical doping levels and operating temperatures of Gunn diodes.

EFFECTS OF CHAOTIC PERTURBATION ON A PERIODIC GUNN OSCILLATOR

We have studied dynamics of a periodic X-band Gunn oscillator (GO) forced by microwave chaotic signals through numerical simulation and by hardware experiment. The chaos used as forcing signal is generated in a periodically driven non-oscillatory GO. Numerical simulation results indicate that the forced periodic GO becomes chaotic for a moderate strength of forcing chaos. The generated chaos in driven GO is found to become phase or general synchronized to the forcing chaos depending on strength of the latter one. Hardware experiments are performed in X-band of microwave frequency. It shows generation of chaos in driven GO due to forcing. Moreover, synchronization between forcing and generated chaos is indirectly verified.

ENERGYEFFICIENT HEAT DISSIPATION THROUGH MULTISTAGE THERMOELECTRIC DEVICE USING GUNN DIODES

The article describes the design of the heat sink on the basis of a multi-stage thermoelectric device implements a method for removing the heat of transformation of the environment by means of radiation through the use of Gunn diodes, which will increase and intensify the processes of heat transfer and energy efficiency of cooling systems.

Bistability and hysteresis in the emergence of pulses in microstrip Gunn-diode circuits

We develop time-domain simulations of microwave and THz radiation sources built as arrays of active devices when the radiation wavelength is small as compared to spacing between electronic components. We pursue an approach when the system is represented by equations with time-delay feedback that could generate chaos and other forms of complicated dynamics. The approach simplifies simulations of ultra-wideband effects and exceeds capabilities of frequency-domain methods. As a model case, we simulated a microstrip circuit with Gunn diode and a remote resonator emitting the radiation towards infinity. We observed the emergence of either the continuous waves or the trains of high-frequency pulses depending on the bias conditions. We found bistability and hysteresis in the onset of different oscillation modes that depends on the way of driving the bias voltage into the domain of instability of the given system. The results would allow one to improve the design of THz radiation sources with time-delay coupling between components.

Experimentally estimated dead space for GaAs and InP based planar Gunn diodes

An experimental method has been used to estimate the dead space of planar Gunn diodes which were fabricated using GaAs and InP based materials, respectively. The experimental results indicate that the dead space was approximately 0.23 μm and the saturation domain velocity 0.96 × 105 m s−1 for an Al0.23Ga0.77As based device, while for an In0.53Ga0.47As based device, the dead space was approximately 0.21 μm and the saturation domain velocity 1.93 × 105 m s−1. Further, the results suggest that the saturation domain velocity is reduced or there is an increase in the dead-space due to local field distortions when the active channel length of the planar Gunn diode is less than 1 micron.

Monte Carlo study of the operation of GaN planar nanodiodes as sub-THz emitters in resonant circuits

A study of the high-frequency performance of GaN-based asymmetric self-switching diodes (SSDs) designed for a room-temperature sub-THz Gunn emission, and connected to a resonant RLC parallel circuit, is reported. With the aim of facilitating the achievement and control of Gunn oscillations, which can potentially allow the emission of THz radiation by GaN SSDs, a time-domain Monte Carlo (MC) theoretical study is provided. The simulator has been validated by comparison with the I–V curves of similar fabricated structures, including the possibility of heating effects. A V-shaped SSD has been found to be more efficient than the square one in terms of the DC to AC conversion efficiency η. Indeed, according to our MC results, a value of η of at least 0.35% @ 270 GHz can be achieved for the V-shaped SSD at room temperature by using an adequate resonant circuit. This value can be increased up to 0.80%, even when considering the heating effects, with appropriate RLC elements. Furthermore, simulations show that when several diodes are fabricated in parallel in order to enhance the emitted power, there is no synchronization between the oscillations of all the SSDs; however, the phase-shift effects can be solved using a synchronized current injection by the attachment of a resonant circuit.

Experimental assessment of anomalous low-frequency noise increase at the onset of Gunn oscillations in InGaAs planar diodes

In this work, the presence of anomalous low-frequency fluctuations during the initiation of higher frequency oscillations in InGaAs-based Gunn planar diodes has been evidenced and investigated. Accurate measurements showing the evolution of the power spectral density of the device with respect to the applied voltage have been carried out. Such spectra have been obtained in the wide frequency range between 10 MHz and 43.5 GHz, simultaneously covering both the low-frequency noise and the fundamental oscillation peak at some tens of GHz. This provides valuable information to better understand how these fluctuations appear and how these are distributed in frequency. For much higher frequency operation, such understanding can be utilized as a simple tool to predict the presence of Gunn oscillations without requiring a direct detection.

Ultra-short channel GaN high electron mobility transistor-like Gunn diode with composite contact

We present a numerical analysis on an ultra-short channel AlGaN/GaN HEMT-like planar Gunn diode based on the velocity-field dependence of two-dimensional electron gas (2-DEG) channel accounting for the ballistic electron acceleration and the inter-valley transfer. In particular, we propose a Schottky-ohmic composite contact instead of traditional ohmic contact for the Gunn diode in order to significantly suppress the impact ionization at the anode side and shorten the “dead zone” at the cathode side, which is beneficial to the formation and propagation of dipole domain in the ultra-short 2-DEG channel and the promotion of conversion efficiency. The influence of the surface donor-like traps on the electron domain in the 2-DEG channel is also included in the simulation.

Effects of Package Parasites on the Dynamics of a Gunn Oscillator

Effects of package inductance and package capacitance on the behavior of microwave Gunn oscillator have been studied analytically and through numerical simulation. In the presence of package parasites the system equation is described by two coupled second order differential equations. Critical examination reveals that for a certain range of magnitudes of the package parasites relative to other device and circuit parameters the system dynamics can become chaotic. However, by the application of an external synchronizing signal of suitable frequency and power, the chaotic dynamics of the oscillator can be controlled. Results of numerical simulation closely agree with the analytical findings.

Effects of Package Parasites on the Dynamics of a Gunn Oscillator

Effects of package inductance and package capacitance on the behavior of microwave Gunn oscillator have been studied analytically and through numerical simulation. In the presence of package parasites the system equation is described by two coupled second order differential equations. Critical examination reveals that for a certain range of magnitudes of the package parasites relative to other device and circuit parameters the system dynamics can become chaotic. However, by the application of an external synchronizing signal of suitable frequency and power, the chaotic dynamics of the oscillator can be controlled. Results of numerical simulation closely agree with the analytical findings.

Structural Dependences of Gunn Oscillations in a Planar Nano-Device

Gunn oscillations in a GaAs-based planar nanodevice are studied using a two-dimensional ensemble Monte Carlo (EMC) method. Current oscillations with a frequency of about 0.1 THz have been observed. The current oscillations are accompanied by electron domain evolution along the nanochannel. As such, they can be attributed to Gunn Effect. Further study shows that the Gunn oscillations are not only bias-dependent, but also structural-dependent. The threshold voltage and the amplitude of the oscillations are both related to the channel width and the asymmetry of the device structure.

Cofabrication of Planar Gunn Diode and HEMT on InP Substrate

We present the cofabrication of planar Gunn diodes and high-electron mobility transistors (HEMTs) on an indium phosphide substrate for the first time. Electron beam lithography has been used extensively for the complete fabrication procedure and a 70-nm T-gate technology was incorporated for the enhancement of the small-signal characteristics of the HEMT. Diodes with anode-to-cathode separation (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ac</sub> ) down to 1and 120-μm width were shown to oscillate up to 204 GHz. The transistor presents a cutoff frequency ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of 220 GHz, with power gain up to 330 GHz ( f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ). The integration of the two devices creates the potential for the realization of high-power, high-frequency MMIC Gunn oscillators, circuits, and systems.

차량 충돌 방지 레이더 시스템 응용을 위한 77 GHz 도파관 전압 조정 발진기

본 논문에서는 차량 충돌 방지 레이더 시스템 응용을 위하여 중심 주파수가 77 GHz인 도파관 (waveguide) 전압조정 발진기 (VCO, voltage controlled oscillator)를 구현하였다. 구현된 도파관 전압 조정 발진기는 GaAs 기반의 건다이오드 (Gunn diode)와 버랙터 다이오드 (varactor diode), 도파관 천이기 (waveguide transition), 저역 통과 필터(LPF, low pass filter) 및 공진기 (resonator) 기능을 동시에 수행하는 다이오드의 바이어스 (bias) 포스트 (post)로 구성되어진다. 77 GHz 신호는 동공 (cavity)을 38.50 GHz에서 발진하도록 설계하여 2체배된 신호를 사용하였으며 WR-12에서 WR-10으로 천이되어 출력된다. 도파관 천이기는 77 GHz의 중심주파수에서 1.86 dB의 삽입손실(insertion loss)과 -30.22 dB의 입력반사계수 (S11, input reflection coefficient) 특성을 갖는다. 제작된 도파관 전압조정 발진기는 870 MHz의 대역폭 (bandwidth)과 12.0 dBm ~ 13.75 dBm의 출력 전력 특성을 나타내었다. 위상잡음 특성은 1 MHz 오프셋 (offset)에서 -100.78 dBc/Hz의 우수한 특성을 얻었다. In this work, we demonstrated a 77 GHz waveguide VCO with transition from WR-12 to WR-10 for anti-collision radar applications. The fabricated waveguide VCO consists of a GaAs-based Gunn diode, a varactor diode, a waveguide transition, and two bias posts for operating as a LPF and a resonator. The cavity is designed for fundamental mode at 38.5 GHz and operated at second hormonic of 77 GHz. The waveguide transition has a 1.86 dB of insertion loss and -30.22 dB of S11 at the center frequency of 77 GHz. The fabricated VCO achieves an oscillation bandwidth of 870 MHz. Output power is from 12.0 to 13.75 dBm and phase noise is -100.78 dBc/Hz at 1 MHz offset frequency from the carrier.

An AlGaAs/GaAs‐based planar Gunn diode oscillator with a fundamental frequency operation of 120 GHz

ABSTRACTThis letter reports the highest fundamental oscillator operating frequency of 120 GHz for gallium arsenide (GaAs)‐based Gunn diode. The letter describes the design, fabrication, and test of the aluminum gallium arsenide (AlGaAs)/(GaAs) planar Gunn diode with an anode to cathode separation of 1 μm and channel width of 120 μm. The planar Gunn diode was designed with an integrated series inductor in coplanar waveguide format. The experimental results showed that the planar Gunn diode oscillated at a fundamental frequency of 120.47 GHz with an RF output power −9.14 dBm. This is highest fundamental frequency and power recorded for a GaAs‐based Gunn diode. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2449–2451, 2014

Numerical and Experimental Studies on the Chaotic Dynamics of Driven Gunn Oscillator

Dynamics of a microwave (X band) Gunn oscillator in presence of a periodic forcing signal has been critically studied to explore the existence of chaos in the behavior of the driven Gunn oscillator (DGO). A broad band continuous spectrum is experimentally observed at the output of the DGO just at the verge of the synchronization band for certain strength and frequency of the forcing signal. For characterisation of the obtained broad band signal, time domain analysis of the frequency down converted DGO output is done and different chaos quantifiers like Maximum Lyapunov exponent and Correlation dimension are evaluated to confirm the chaotic mode of oscillations. Numerical simulation of the system equations also indicate that the dynamics of the DGO enters into a chaotic domain at these conditions.

Studies on Dynamics of Driven Bilaterally Coupled Gunn Oscillator

The dynamics of bilaterally coupled Gunn oscillator driven by external periodic signal has been examined through numerical simulation and experimental observation. The coupling factors between the two oscillators in either path as well as the strength and frequency of the external periodic driving signals are key parameters to control the dynamics of Driven Bilaterally Coupled Gunn Oscillator (DBCGO) system. The numerical study explores the possibility of generation of controllable chaotic signals in DBCGO system. The present work also considers this method through a hardware experiment. For different set of coupling factors, driving signal strength and frequencies, chaotic oscillations are observed. Therefore, the DBCGO system with suitable couplings and driving signal conditions can be considered as a potential source of chaotic signals in microwave frequency range.

Studies on Dynamics of Driven Bilaterally Coupled Gunn Oscillator

Studies on Dynamics of Driven Bilaterally Coupled Gunn Oscillator

Integration techniques of pHEMTs and planar Gunn diodes on GaAs substrates

This work presents two different approaches for the implementation of pseudomorphic high electron mobility transistors (pHEMTs) and planar Gunn diodes on the same gallium arsenide substrate. In the first approach, a combined wafer is used where a buffer layer separates the active layers of the two devices. A second approach was also examined using a single wafer where the AlGaAs/InGaAs/GaAs heterostructures were designed for the realisation of pHEMTs. The comparison between the two techniques showed that the devices fabricated on the single pHEMT wafer presented superior performance over the combined wafer technique. The DC and small-signal characteristics of the pHEMTs on the single wafer were enhanced after the use of T-gates with 70nm length. The maximum transconductance of the transistors was equal to 780mS/mm with 200GHz maximum frequency of oscillation (fmax). Planar Gunn diodes fabricated in the pHEMT wafer, with 1.3μm anode-to-cathode separation (LAC) presented oscillations at 87.6GHz with maximum power of oscillation equal to −40dBm.

Superconductor-Insulator-Superconductor Mixers for the 2 mm Band (129-174 GHz)

We present the design, construction and performance of backshort-tuned Single Side Band (SSB) and of fixed-tuned Double Side Band (DSB) Superconductor-Insulator-Superconductor (SIS) mixers covering the frequency range of 129-174 GHz (2 mm band). Receivers employing these SSB mixers have been continuously operated for astronomical observations on the six antennas of the IRAM Plateau de Bure Intereferometer (PdBI) since 2007 and on the IRAM 30 m Pico Veleta (PV) radio telescope since 2009. The DSB version of the mixer was employed in a prototype of a four-element focal plane array that was tested on the IRAM 30 m radio telescope. Both SSB and DSB mixers employ the same chip and are based on a wideband single ended probe transition from WR6 full-height waveguide to thin-film microstrip line and on a series array of two Nb/Al-AlOx/Nb junctions. The measured receiver noise for the four-element DSB mixer array pumped by a Gunn oscillator cascaded with a frequency doubler was in the range 25-35 K across the 135-168 GHz LO band. The PdBI and PV receivers equipped with the SSB mixers have measured noise temperatures in the range of 30 K to 60 K and an image sideband rejection below -10 dB over the 129-174 GHz RF band. The measurement results agree well with the predictions obtained through detailed simulations of the SIS receivers based on the standard theory of quantum mixing.

Peculiarities of Noise Characteristics of Autodynes Under Strong External Feedback

Results are presented of a quasistatic analysis of the noise characteristics of an autodyne operating under the action of its own reflected radiation with its own internal noise taken into account. Periodic non-stationarity of the root-mean-square value of the phase, frequency, and amplitude noise levels is established, which is manifested when the distance to the reflecting object is varied. It is shown that the given phenomenon is observed upon increase of the level of reflected radiation, when the magnitude of the external feedback parameter of the autodyne system becomes comparable to unity. Results of our own experimental studies of a hybrid-integrated oscillator based on a Gunn diode, and also results published in other works for avalanche transit-time diode oscillators and autodynes based on laser diodes, have confirmed the conclusions of our theoretical analysis.