Planar Gunn Diode Research Articles

Monte Carlo Study of Gunn Oscillations in Geometrically Shaped Planar Gunn Diodes Based on Doped GaN: Influence of Geometry, Intervalley Energy, and Temperature

Monte Carlo Study of Gunn Oscillations in Geometrically Shaped Planar Gunn Diodes Based on Doped GaN: Influence of Geometry, Intervalley Energy, and Temperature

On the Practical Limitations for the Generation of Gunn Oscillations in Highly Doped GaN Diodes

Planar Gunn diodes based on doped GaN active layers with different geometries have been fabricated and characterized. Gunn oscillations have not been observed due to the catastrophic breakdown of the diodes for applied voltages around 20–25 V, much below the bias theoretically needed for the onset of Gunn oscillations. The breakdown of the diodes has been analyzed by pulsed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{I}$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}$</tex-math> </inline-formula> measurements at low temperatures, and it has been observed to be almost independent of the geometry of the channels, thus allowing to discard self-heating effects as the origin of the device burning. The other possible mechanism for the device failure is an impact-ionization avalanche due to the high electric fields present at the anode corner of the isolating trenches. However, Monte Carlo simulations using the typical value of the intervalley energy separation of GaN, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon_{\text{1}-\text{2}}$</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 2.2 eV, show that impact ionization mechanisms are not significant for the voltages for which the experimental failure is observed. But recent experiments showed that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon_{\text{1}-\text{2}}$</tex-math> </inline-formula> is lower, around 0.9 eV. This lower intervalley separation leads to a much lower threshold voltage for the Gunn oscillations, not far from the experimental breakdown. Therefore, we attribute the device’s failure to an avalanche process just when Gunn domains start to form, since they increase the population of electrons at the high electric field region, thus strongly enhancing impact ionization mechanisms that lead to the diode failure.

Virtual Simulator

This paper is based on virtual experiment approaches to Gunn diode and their vi characteristics. Virtual labs which provide remote-access to simulation-based Labs in various disciplines of Science and Engineering. In microwave and radar engineering, virtual experiments are not available. In this paper, we consider vi characteristics of Gunn diode. In this experiment without actual use of power supply we performing experiment virtually. Evaluation using web technology we introduced this experiment. Gunn devices were simulated using the Sentaurus Device software. The fabricated planar Gunn diodes are 1.3 μm long and 120 micron wide and the measured and simulated results are in excellent agreement. This experiment involving the changes in current and voltage. We further show applications and experiment actual and virtual setup.

Optimization of the Epilayer Design for the Fabrication of Doped GaN Planar Gunn Diodes

Optimization of the Epilayer Design for the Fabrication of Doped GaN Planar Gunn Diodes

Comprehensive characterization of Gunn oscillations in In0.53Ga0.47As planar diodes

In this work, In0.53Ga0.47As planar Gunn diodes specifically designed for providing oscillations at frequencies below 30 GHz have been fabricated and characterized. Different types of measurements were used to define a set of consistent methods for the characterization of the oscillations that can be extended to the sub-THz frequency range. First, negative differential resistance and a current drop are found in the I–V curve, indicating the potential presence of Gunn oscillations (GOs), which is then confirmed by means of a vector network analyzer, used to measure both the S 11 parameter and the noise power density. The onset of unstable GOs at applied voltages where the negative differential resistance is hardly visible in the I–V curve is evidenced by the observation of a noise bump at very low frequency for the same applied voltage range. Subsequently, the formation of stable oscillations with an almost constant frequency of 8.8 GHz is observed for voltages beyond the current drop. These results have been corroborated by measurements performed with a spectrum analyzer, which are fully consistent with the findings achieved by the other techniques, all of them applicable to Gunn diodes oscillating at much higher frequencies, even above 300 GHz.

Investigation of High-Frequency Fine Structure in the Current Output of Shaped Contact Planar Gunn Diodes

A novel gallium arsenide (GaAs) planar Gunn diode design with shaped anode and cathode contacts using Monte Carlo simulations has been shown to produce significantly higher frequency fine structure components in the output waveform than the natural transit time frequency of the diode. We have investigated devices without a feedback potential and devices with a feedback potential (in the delayed mode) and have shown 350-GHz fine structure frequency components in a device with a nominal transit time frequency of 70 GHz is possible. This is the first observation of such stable repeating high-frequency components in a Gunn diode, giving potential for very high-frequency power generation and other wave-shaping applications.

Thermal Analysis of AlGaN/GaN Hetero-Structural Gunn Diodes on Different Substrates Through Numerical Simulation

GaN-based planar Gunn diodes are promising terahertz sources for monolithic microwave and terahertz integrated circuits (MMICs and MTICs, respectively) due to high output power and easiness of fabrication and circuit integration. However, high lateral current in the 2DEG channel may lead to failures such as early breakdown and suppression of oscillations. In this paper, we will, for the first time, systematically investigate the thermal effect on DC IV and output RF characteristics of AlGaN/GaN hetero-structural planar Gunn diodes on different substrates including diamond, SiC, Si and sapphire. Our simulation results show that the best RF output performance comes with the devices on diamond substrate and no oscillating current is observed for devices on sapphire substrate. The suppress of Gunn oscillation in the device on sapphire is mainly due to the excessive heat generated in the channel that leads to increase of the dead zone and attenuation of electronic domains. These results will lay theoretical and experimental foundation for realizing not only milliwatt GaN-based terahertz semiconductor oscillators but also other power devices.

Investigation of THz Frequency Shaped Anode Planar Gunn Diodes Operating in Delayed Mode

A novel planar design of Gunn diode with a shaped anode contact, utilizing Monte Carlo simulations, has been shown to have produced 0.3 THz frequency current output when operated in delayed mode. Two novel anode designs are investigated here, one with two fixed distances, and the other with three fixed distances between the cathode and anode electrodes. The corresponding waveforms generated, show two and three current peaks respectively. The work suggests high frequency and novel wave-shaping applications are possible in such devices.

Investigation of Contact Edge Effects in the Channel of Planar Gunn Diodes

The effect of the edge of the channel on the operation of planar Gunn diodes has been examined using Monte Carlo simulations. High fields at the corner of the anode contact are known to cause impact ionization and consequent electroluminescence, but our simulations show that the Gunn domains are attracted to these corners, perturbing the formation of the domains, which can lead to chaotic dynamics within the rest of the channel leading to uneven heating and reduced RF output power. We show how novel shaping of the electrical contacts at the ends of the channel reduces the attraction and restores the domain wavefronts for good device operation.

An electrical equivalent circuit to simulate the output power of an AlGaAs/GaAs planar gunn diode oscillator

AbstractThe planar Gunn diode offers the potential of microwave, milli‐metric and THz‐based oscillators, which can be fabricated as part of a microwave monolithic integrated circuit (mmic). The paper develops an electrical representation of an aluminum gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4 μm and width of 120 μm, embedded in an oscillator circuit. The work indicates a maximum simulated RF output power of +5 dBm compared with published experimental results of −19 dBm for similar diodes.

Thermal Profiles Within the Channel of Planar Gunn Diodes Using Micro-Particle Sensors

This letter describes the use of a novel micro-particle sensor ( ${\sim }3{\mu }\text{m}$ diameter) and infra-red microscopy to measure the temperature profile within the active channel (typically 3- ${\mu }\text{m}$ length and 120- ${\mu }\text{m}$ width) of planar Gunn diodes. The method has enabled detailed temperature measurements showing an asymmetrical temperature profile along the active width of these devices. The asymmetrical temperature profile suggests a similar behavior in the channel current density, which may contribute to the lower than expected RF output power.

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.

Investigation on multi-frequency oscillations in InGaAs planar Gunn diode with multiple anode-cathode spacings

Abstract Current oscillations in an AlGaAs/InGaAs/AlGaAs-based two-dimensional electron gas (2DEG)-based hetero-structure have been investigated by means of semiconductor device simulation software SILVACO, with an interest on the charge domain formation at large biases. Single-frequency oscillations are generated in planar Gunn diodes with uniform anode and cathode contacts. The oscillation frequency reduces as the applied bias voltage increases. We show that it is possible to create multiple, independent charge domains in a novel Gunn diode structure with designed multiple anode-cathode spacings. This enables simultaneous generation of multiple frequency oscillations in a single planar device, in contrast to traditional vertical Gunn diodes where only single-frequency oscillations can be achieved. More interestingly, frequency mixing in multiple-channel configured Gunn diodes appeared. This proof-of-concept opens up the possibility for realizing compact self-oscillating mixer at millimeter-wave applications.

Simulation investigation of multiple domain observed in In0.23Ga0.77As planar Gunn diode

A numerical study for an AlGaAs/InGaAs-based quantum well structure planar Gunn diodes was performed by initially proposing imperfect metallic contacts that can introduce multiple anode–cathode spacings caused by etching process during the fabrication. Through Fast Fourier transform (FFT) algorithm, the result reveals that, at moderate bias voltage above the threshold, multi-channel planar Gunn diode exhibits multiple oscillations which were consistent with experimental observation due to non-uniformity of contact terminal. A downwards shift of oscillation frequency by varying the applied voltage across terminal was observed due to Gunn effect. The finding may be utilized not only to generate multiple millimeter wave or even terahertz signal sources on single chip, but also to achieve frequency tunability through tuning the applied bias voltage.

Modulation of the domain mode in GaN‐based planar Gunn diode for terahertz applications

AbstractThis paper reports the modulation of the domain mode in the 2DEG channel of GaN HEMT‐like Gunn diodes by adjustment the electron concentration of the 2DEG near the cathode side. The enhancement of the electron concentration near the cathode side promotes the fast formation of the dipole domain layer and greatly reduces the dead zone length, which increases the RF output power. The employment of the recess layer near the cathode reduces the electron concentration of the 2DEG beneath it, which acts as a notch‐doped layer as in the bulk vertical diode. The reduction of the electron concentration of the 2DEG near the cathode promotes the formation of dual‐domain in one oscillation circle, which aims to enhance harmonic components of Gunn oscillation so as to minimize the use of frequency multipliers for SMMW and THz operation. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Extraction of second harmonic from an InP based planar Gunn diode using diamond resonator for milli-metric wave frequencies

Planar Indium Gallium Arsenide (In0.57Ga0.47As) 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 In0.57Ga0.47As planar Gunn diodes were designed with an active length of 4μm, channel width of 120μm 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 (121.68GHz) with an RF output power of −14.1dBm. This is highest recorded power at the second harmonic from a planar Gunn diode.

The enhancement of the output characteristics in the GaN based multiple‐channel planar Gunn diode

We present an explicit numerical analysis on GaN‐based multi‐quantum‐well planar Gunn diodes. The simulation demonstrates that Gunn oscillations generated in the multi‐channel can be self‐synchronized to each other, which significantly improves the output characteristics of planar Gunn diode due to the superposition of the dipole domain in each channel. The optimized output characteristics are obtained in the triple‐channel Gunn diode, where the RF output power is about 6.45 mW and the DC‐to‐RF conversion efficiency is about 2.39% at the fundamental frequency of 216.05 GHz, more than three times larger than that of the single‐channel AlGaN/GaN Gunn diode. The proposed GaN HEMT‐like multi‐channel planar Gunn diode with higher level of output characteristics shows great potential as a solid‐state radiation source of millimeter‐wave and sub‐terahertz.

The modulation of multi-domain and harmonic wave in a GaN planar Gunn diode by recess layer

In this paper, a novel structure of a gallium nitride (GaN) planar Gunn diode with isosceles trapezoidal recess layers in the aluminum gallium nitride (AlGaN) barrier layer is proposed to enhance the harmonic components of Gunn oscillation waveforms. Numerical simulations demonstrate that the oscillation frequency rises from 99.1 GHz up to 300.4 GHz with the recess number increasing from one to four, at which the maximum radio frequency (RF) output power and conversion efficiency are obtained. The output performance of the diode enhances at high harmonic frequencies and is mainly due to the multiple recess layer structure that can trigger the formation of multiple Gunn domains in the two-dimensional electron gas channel of the GaN planar Gunn diode. This indicates that the long channel GaN Gunn diode has the ability to output the available RF power associated with the device operating in a submillimeter-wave and terahertz (THz) regime.

On the radiation resistance of planar Gunn diodes with δ-doped layers

The radiation resistance of planar Gunn diodes is investigated. Based on the results of measurements of the pulsed current–voltage characteristics and computer simulations it is shown that the use of δ layers of doping impurities contributes to the higher radiation resistance of planar diodes by an order of magnitude compared to conventional Gunn diodes. The results of this study make it possible to formulate methodical guidelines to reduce the amount of computational and experimental studies without a considerable decrease in their informativity.

Electroluminescence from GaAs/AlGaAs Heterostructures in Strong in-Plane Electric Fields: Evidence for k- and Real-Space Charge Transfer

In the Gunn effect, which occurs in certain semiconductors in strong electric fields, electrons are driven out of a low-mass central valley into a heavy-mass side valley in k (momentum) space, ultimately resulting in negative differential resistance (NDR). Recently, there has been interest in the possibility of exploiting this phenomenon in heterostructured semiconductors, as a means to realize novel terahertz sources. Here, we demonstrate that a GaAs/AlGaAs heterostructure planar Gunn diode exhibits both NDR and electroluminescence (EL), the characteristics of which are consistent with the combined action of simultaneous k-space and real-space electron transfer. By making simultaneous electrical-transport and EL measurements, we reveal the following scenario as a function of the applied voltage. At sufficiently large bias, the onset of k-space transfer gives rise to NDR and results in the formation of traveling high-field domains. As each domain travels toward the anode, impact ionization taking place wi...