Gunn Diode Research Articles

Temperature effect on the submicron AlGaN/GaN Gunn diodes for terahertz frequency

The wurtzite AlGaN/GaN Gunn diode with tristep-graded Al composition AlGaN as hot electron injector is simulated by using an improved negative differential mobility model of GaN. The results show that the oscillation mode of Gunn diode gradually shifts from dipole domain mode toward accumulation mode with increase in temperature, and the mode shift closely depends on the injector length. At the temperatures of 300–400 K, 0.6 and 0.4 μm Gunn diodes normally generate the oscillation of dipole domain mode, yielding the fundamental oscillation frequencies of 332–352 GHz and 488–508 GHz, respectively, with the dc/rf conversion efficiencies of 2%–3% and the output power densities of 109–1010 W cm−3. At higher temperatures, the diodes generate the accumulation mode oscillation, and the highest frequency approaches 680 GHz and 977 GHz, respectively, with the dc/rf conversion efficiencies of 0.5%–1%.

Device loading effect on nonresonant detection of terahertz radiation in dual grating gate plasmon‐resonant structure using InGaP/InGaAs/GaAs material systems

AbstractWe report on nonresonant detection of terahertz radiation using our original InGaP/InGaAs/GaAs plasmon‐resonant high‐electron‐mobility transistor having a dual grating gate (DGG) structure. The experiments were performed at room temperature using a Gunn diode operating at 0.30 THz as the THz source. Using a device‐loading model, the intrinsic responsivity was extracted and was dependent on the polarization of the incident THz wave. The device exhibited highest response when the electric‐field vector of the incident THz radiation was directed in the source‐drain direction. The 2D spatial distribution image of the transistor responsivity shows a clear beam focus centred on the transistor position, which proves the appropriate coupling of the THz radiation to the device, due to the DGG structure. The device also showed a high intrinsic responsivity of ∼90 V/W and a noise equivalent power (NEP) as low as ∼10‐10 WHz‐0.5. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

STUDIES ON THE DYNAMICS OF BILATERALLY COUPLED X-BAND GUNN OSCILLATORS

The dynamics of a system comprising of two bilaterally coupled Gunn oscillators (BCGOs) has been examined using a circuit theoretic model of the Gunn oscillator (GO). The efiects of coupling factors (kij) between i-th and j-th oscillators on the frequency-range of synchronized operation and the magnitude of common frequency of oscillation have been examined semi-analytically and by numerical solution of the system equations. The occurrence of chaotic oscillations at the verge of synchronization bands is observed in numerical simulation. The experimental response of the BCGO operating in the X-band is obtained and the results are found to be qualitatively similar to the analytical and numerical predictions.

Contact shaping in planar Gunn diodes

AbstractThe production of Gunn diodes with a planar architecture provides the ability to easily specify contact separation, and hence device transit region length, through lithographic processing. Beyond manufacturing and integration benefits, this also enables the production of devices whose contacts are intentionally and controllably non‐uniform over their width. Through such shaping of the contacts, the morphology of the Gunn domains may also be controlled. This has demonstrated potential for improving device performance, both with regard to operating frequency and oscillation amplitude, by at least ∼30% and ∼100% respectively. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Novel composite contact design and fabrication for planar Gunn devices for millimeter‐wave and terahertz frequencies

AbstractContacts to planar Gunn devices on the semiconductor surface suffer from high electric field stress and current crowding leading to premature burn out. We have developed a new composite contact design using a Schottky extension of the conventional Ohmic contact. The composite contact structures have been fabricated and tested to mitigate the effects of high concentrations of charge and high electric fields at the anode edge of the planar Gunn diode. Monte Carlo simulations confirm these experimental results in composite contacts. These results suggest a mechanism of increased lifetime when using composite contacts as compared to conventional Ohmic contacts. This is of significant importance for planar Gunn device operation at millimetre wave and terahertz frequencies where high doping density (∼1017cm‐ 3) and short cathode to anode separation (1µm or less) is required. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Design and manufacture of planar GaAs Gunn diode for millimeter wave application

GaAs-based planar Gunn diodes with AlGaAs hot electron injector have been successfully developed to be used as a local oscillator of 76 GHz in monolithic millimeter-wave integrated circuits. We designed two kinds of structure diode, one has a fixed distance between the anode and cathode, but has variational cathode area, the other has a fixed cathode area, but has different distances between two electrodes. The fabrication of Gunn diode is performed in accordance with the order of operations: cathode defining, mesa etching, anode defining, isolation, passivation, via hole and electroplating. A peak current density of 29.5 kA/cm2 is obtained. And the characteristics of negative differential resistance and the asymmetry of the current—voltage curve due to the AlGaAs hot electron injector are discussed in detail. It is demonstrated that the smaller size of active area corresponds to the smaller current, and the shorter distance between anode and cathode also corresponds to the lower threshold voltage and higher peak current, and hot electron injector can effectively enhance the radio frequency conversion efficiency and output power.

Rapid evaluation of doping-spike carrier concentration levels in millimetre-wave GaAs Gunn diodes with hot-electron injection

This paper describes a novel method for fast, accurate evaluation of doping-spike carrier concentrations in hot-electron injected GaAs Gunn diodes. The technique relies on current asymmetry measurements obtained using pulsed-dc testing of on-wafer quasi-planar Gunn diode test structures, which removes the need for full device fabrication. Small changes in carrier concentration can easily be detected (at a nominal value of 1 × 1018 cm−3) and a greater sensitivity than conventional techniques is demonstrated at the doping levels used. In addition, test structure fabrication can be integrated into the initial Gunn diode front side production process allowing a rapid in-process test to be carried out thus leading to a significant reduction in material characterization cycle time.

Development of GaAs Gunn Diodes and Their Applications to Frequency Modulated Continuous Wave Radar

In this work, we have designed and fabricated the GaAs Gunn diodes for a 94 GHz waveguide voltage controlled oscillator (VCO) which is one of the important parts in a frequency modulated continuous wave (FMCW) radar application. For fabrication of the high power GaAs Gunn diodes, we adopted a graded gap injector which enhances the output power and conversion efficiency by effectively removing the dead-zone. We have measured RF characteristics of the fabricated GaAs Gunn diodes. The operating current, oscillation frequency, and output power of the fabricated GaAs Gunn diodes are presented as a function of the anode diameters. The operating current increases with anode diameters, whereas the oscillation frequency decreases. The higher oscillation frequency was obtained from 60 µm anode diameters of the fabricated Gunn GaAs diodes and higher power was obtained from 68 µm. Also, for application of the 94 GHz FMCW radar system, we have fabricated the 94 GHz waveguide VCO. From the fabricated GaAs Gunn diodes of anode diameter of 60 µm, we have obtained the improved VCO performance.

A Novel SIW-Based Planar W-Band GaAs Gunn Harmonic Oscillator

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.

Phase and Amplitude Drift Research of Millimeter Wave Band Local Oscillator System

In this paper, we developed a local oscillator (LO) system of millimeter wave band receiver for radio astronomy observation. We measured the phase and amplitude drift stability of this LO system. The voltage control oscillator (VCO) of this LO system use the 3 mm band Gunn oscillator. We developed the digital phase locked loop (DPLL) module for the LO PLL function that can be computer-controlled. To verify the performance, we measured the output frequency/power and the phase/amplitude drift stability of the developed module and the commercial PLL module, respectively. We show the good performance of the LO system based on the developed PLL module from the measured data analysis. The test results and discussion will be useful tutorial reference to design the LO system for very long baseline interferometry (VLBI) receiver and single dish radio astronomy receiver at the 3 mm frequency band.

Current-controlled negative differential resistance effect induced by Gunn-type instability in n-type GaN epilayers

High-field carrier transport properties probed by pulsed current-voltage characteristics in n-type GaN epilayers have been investigated at room temperature. The threshold electric field of the Gunn effect is experimentally determined to be about 400 kV/cm with an electron peak velocity of about 1.9×107 cm/s. The current-controlled negative differential resistance effect induced by the Gunn-type instability in n-type GaN is observed, which takes the early electric breakdown of the GaN epilayers in charge.

Two-dimensional interferometric and synthetic aperture imaging with a hybrid terahertz/ millimeter wave system

We have developed an interferometric synthetic aperture incoherent imaging system at 94 GHz, in which a high-power electronic millimeter wave source (Gunn Oscillator) is integrated with a continuous-wave terahertz (THz) photomixing detection system to achieve a high signal-to-noise ratio. Imaging of a point source located 10?m away from the detector array is presented. Two-dimensional THz reflective images of an extended object with different shapes are reconstructed with only four detectors by use of rotational synthesis.

Ka‐band substrate integrated waveguide voltage‐controlled Gunn oscillator

AbstractA Ka‐band substrate integrated waveguide (SIW) voltage‐controlled oscillator (VCO) is demonstrated using GaAs Gunn diode.GaAs hyperabrupt varactor is employed in parallel to the Gunn diode for low phase noise and wideband tuning. The VCO achieves a tuning range of more than 1 GHz by varying the varactor tuning voltage between 0 V and 9 V, and phase noise of −102.1 dBc/Hz at 1 MHz offset from a 36 GHz carrier frequency. The output power varies from 9.3 dBm to 11.3 dBm within the tuning range. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1232–1235, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25169

Low Noise Second Harmonic Oscillator Using Mutually Synchronized Gunn Diodes

This paper represents a low noise second harmonic oscillator using mutually synchronized Gunn diodes. A multi-layer MIC technology is adopted to reduce the circuit size of the oscillator. The oscillator consists of Gunn diodes, slot line resonators and strip lines. By embedding Gunn diodes in the slot line resonators, a harmonic RF signal can be generated very easily. The strip lines are used for the power combining output circuit. The shape of slot line resonator is square in order to achieve the low phase noise and the suppression of undesired harmonics. The second harmonic oscillator is designed and fabricated in K band. The output power is +8.89dBm at the design frequency of 18.75GHz (2f0) with the phase noise of -116.2dBc/Hz at the offset frequency of 1MHz. Excellent suppression of the undesired fundamental frequency signal (f0) of -33dBc is achieved. Also, the circuit size is reduced by three-tenths relative to that of the previously proposed circuit.

APPLICATION OF THE IMPROVED MATRIX TYPE FDTD METHOD FOR ACTIVE ANTENNA ANALYSIS

An improved flnite-difierence time-domain (FDTD) method has been extended to analyze the antennas with complicated lumped/active networks in this paper. The improved FDTD method is based on a novel integral transform and the matrix theory. Combining the novel integral transform with Kirchhofi's circuit laws, the hybrid networks comprised of high order linear and nonlinear elements with arbitrary connection can be modeled by a stable matrix equation. An efiective model is built for linear lumped networks including internal independent sources. A wire antenna loaded with wideband match network and a two-element active patch antenna loaded with Gunn diodes are analyzed by the developed techniques. The analysis results indicate that the improved matrix-type FDTD method is not only sta- ble and accurate, but also time-saving in simulating the complicated hybrid networks.

InP Gunn Diodes with Current Limiting Contact for High Efficiency Gunn Oscillators

We fabricated and examined current limiting effect for InP Gunn diodes with stable depletion layer mode operation of diodes for high efficiency Gunn oscillators. Current limiting at the cathode was achieved by a shallow Schottky barrier at the interface. We discussed fabrication procedure, the results for negative differential resistance and rf tests for InP Gunn diodes. It was shown that the fabricated Gunn diodes have the output power of 10.22dBm at a frequency of 90.13GHz. Its input voltage and corresponding current were 8.55V and 252mA, respectively.

Low Noise Receivers Based on Superconducting Niobium Nitride Hot Electron Bolometer Mixers from 0.65 to 3.1 Terahertz

SUMMARY Low noise terahertz (THz) receivers based on superconducting niobium nitride (NbN) hot electron bolometer (HEB) mixers have been designed, fabricated and measured for applications in astronomy and cosmology. The NbN HEB mixer consists of a planar antenna and an NbN bridge connecting across the antenna’s inner terminals on a high-resistivity Si substrate. To eliminate the influence of direct detection and instability of the local oscillation (LO) power, a wire grid has been used to change the input LO power for compensating the shift of bias current during Y-factor measurement. The double sideband (DSB) receiver noise temperatures at 4.2 K without corrections have been measured from 0.65 to 3.1 THz. The excess quantum noise factor β of about 4 has been obtained, which agrees well with the calculated value. Allan variance of the HEB has been characterized, and Allan time TA longer than 0.4 s is obtained. We also estimated the temperature resolution of the HEB from the Allan variance and obtained the minimum temperature resolution of 1.1 K using a Gunn oscillator with its multipliers at 0.65 THz as an LO source.

Numerical simulation of charge packet behavior in low-density polyethylene based on Gunn effect-like model

Packet-like space charge behavior usually induces the electric field distortion and strongly affects the electrical performance of low-density polyethylene. In this paper, we analyze the influence of charge injection, carriers migration and interaction between the free charge and trap in polyethylene on packet-like space charge behavior and introduce the mechanism of Gunn effect to describe the generating process of space charge packet. Based on this, we simulated two kinds of packet-like space charge behaviors with different variation trends and in different applied fields reported by different research groups. The simulated space charge packet shows very good fitting with the experiment data in both packet amplitude and migration velocity. The simulation results also indicate that the injection conditions and trap level depth play an important role in the diversity of packet-like space charge behavior.

Analysis on suitability of pure and α-Histidine doped KDP crystals in high speed applications

Ferroelectric Potassium Dihydrogen Phosphate (KDP) crystals are widely used in modern short wavelength laser techniques, non-linear and integrated optics. The pure and α-Histidine doped KDP crystals were procured from SRM Institute of Science and Technology, Chennai. The presence of additive in the doped KDP crystal is confirmed through X-Ray diffraction patterns and the lattice parameters were evaluated. Also, Fourier Transform Infrared spectrum confirms the presence of α-Histidine in the doped crystals. The dielectric behaviour of the pure and doped crystals have been studied in the microwave region using K-band microwave bench equipped with the Gunn oscillator and guided with rectangular wave guide.

Novel planar Gunn diode operating in fundamental mode up to 158 GHz

We show the experimental realisation of fundamental mode operation of planar Gunn diode structures fabricated in GaAs/AlGaAs quantum wells. The electron density in the active channel is enhanced by positioning double delta-doping layers on either side. Small signal measurement shows that a typical device exhibits negative resistance up to 158 GHz. Using this device structure we have demonstrated a planar Gunn oscillator working at 115.5 GHz with an output power of -28 dBm.