Impact Avalanche Transit Time Research Articles

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Edge-Terminated AlGaN/GaN/AlGaN Multi-Quantum Well Impact Avalanche Transit Time Sources for Terahertz Wave Generation

Bias Current Modulation of DC and RF Properties of AlmGa1‐m∼GaN Heterojunction IMPATT at Sub‐Millimeter Wave Frequency

Large signal RF properties of double drift region (DDR) Impact Avalanche Transit Time (IMPATT) device based on AlmGa1-m∼GaN heterojunction (HT) are investigated and their variation with bias currents has been presented here. These RF properties and their modulation will significantly validate the acceptability of the particular HT in the sub-millimeter wave frequency domain. Avalanche noise plays the prime ground for making the IMPATT diode basically noisy and tunneling decays the performance of the device, as we move towards the higher frequency range like the sub-millimeter frequency. These setbacks can be done with if the homojunction (HM) is replaced by heterojunction. This authenticates the choice of heterojunction over homojunction. Here, the author takes 500 GHz as the frequency of concern in the sub-millimeter wave range. Here, two complementary heterojunctions of AlmGa1-m∼GaN is taken with m = 0.4 or the mole fraction of Al in the alloy being 40% and their RF results are compared with two homojunctions of GaN and AlGaN for double drift region (DDR) IMPATT diode. Outcomes indicate that HT diodes surpass the high-frequency performance of HM diodes if compared on the basis of dc to RF conversion efficiency and output power due to the influence of large amplitude ac signal. It is also observed that with increasing bias voltage dependent current, which is varied from 20 × 108 to 40 × 108 Am−2, the efficiency of conversion together with the power output increases. These results will be very important for further research in this domain.

Optimal Design of Large Signal Performance of AlN/GaN Hetero-Structural IMPATT and MITATT Diodes

Hetero-structure of AlxGa1-xN/GaN exhibits important applications in high frequency and large power devices. In this paper, AlN/GaN is adopted to optimal design the large power impact avalanche transit time (IMPATT) and mixed tunneling avalanche transit time (MITATT) diodes operating at the atmospheric low loss window frequency of 0.85 THz. The static state and large signal characteristics of the devices are numerically simulated. The values of peak electric field strength, break-down voltage, avalanche voltage, the maximum generation rates of avalanche and tunneling, admittance-frequency relation, output power, conversion efficiency, quality factor of the proposed hetero-structural IMPATT and MITATT diodes are calculated, respectively. Via comparing the obtained results of (n)AlN/(p)GaN and (n)GaN/(p)AlN IMPATT diodes to those of the MITATT counterparts, there exists little performance difference between IMPATT and MITATT devices while implies significant difference between the (n)AlN/(p)GaN and (n)GaN/(p)AlN diodes.

Optimal Design of Large Signal and Noise Performance of GaN/SiC Hetero-Structural IMPATT Diodes Based on QCDD Model

Successes of GaN and SiC electronics in high frequency, large power realm indicate that, the GaN/SiC hetero-structures can be used to design the impact avalanche transit time (IMPATT) diodes operating at Terahertz range, of which holds advantages over homo-structural counterparts in lower noise and reduced tunnel current. Here, the (n)GaN/(p)SiC and (p)GaN/(n)SiC double drift region (DDR) IMPATT diodes operating at 0.85 THz are proposed based on the quantum corrected drift-diffusion (QCDD) model, the performance parameters of static state, large signal and noise properties of the studied devices such as peak electric field intensity, breakdown voltage, optimal negative conductance, output power, conversion efficiency, admittance-frequency relation, quality factor, noise electric field, mean-square noise voltage per band-width and noise measure were numerically calculated and analyzed, which can guide to optimize the GaN/SiC IMPATT diodes.

Low Noise Multiquantum Well DAR IMPATT Diodes Based On SiXGe1-X/Si

A Multiquantum Well (MQW) SixGe1-x/Si DAR (Double Avalanche Region) IMPATT (Impact Avalanche Transit Time) diode as a high power-high efficiency-low noise source at W-band is proposed in this paper. The RF power, conversion efficiency and noise of the device are optimized with respect to number of quantum wells and Ge mole fraction. The proposed device delivers peak power of 2.7 W, conversion efficiency of 7.5% and noise measure of 25 dB when the number of wells in the MQW structure is four and mole fraction of Ge is 0.3. The admittance plots of the device exhibit distinct negative conductance bands for three different (0.1, 0.2 and 0.3) mole fractions of Ge. An upward shift of optimum frequency is observed with increasing Ge mole fraction. The noise measure of the device decreases with increasing mole fraction of Ge and decreasing current.

Relative Study on MM-Wave Performance of Group IV-IV and Group III-V Materials Based IMPATT Sources

A comparative study is done on Si, 4H-SiC, Wz-GaN and InP based impact avalanche transit time (IMPATT) diodes operating at 94 GHz. A double-iterative simulation procedure is utilized to investigate the DC and small-signal features of the diodes from which corresponding avalanche response times and transit times are obtained. The studies exhibit that SiC and GaN diodes are potential sources for radiating high power at 94 GHz. It is also observed that SiC and GaN diodes are highly appropriate for mm-wave frequency bands due to shorter values of their avalanche response time. The power output for SiC IMPATT source is noticed as 47.61 W and for GaN IMPATT, the same is seen as 1.96 W; corresponding avalanche response times are found to be 2.42 × 10−15 and 3.45 × 10−16 s respectively.

Computation of quantum‐corrected noise in graphene‐SiC‐based impact avalanche transit time diode

AbstractHere, we have performed the noise analysis in graphene‐SiC‐based double drift region impact avalanche transit time diode (IMPATT). For computation, the noise model taken is based on drift diffusion with quantum corrections. Though noise computation in IMPATT with classical drift diffusion model are widely followed in earlier years, noise analysis through classical drift diffusion model is independent of confinement and tunneling due to quantum effects. Noise computed through quantum‐corrected noise model is more accurate to measured noise. Therefore, by considering quantum effects in addition to classical noise model, we have computed the noise in graphene‐SiC IMPATT. The noise performance of graphene‐SiC IMPATT is evaluated at Ka band which ranges from 26.5 to 40 GHz. The obtained noise from graphene‐SiC IMPATT is in good agreement with earlier reported noise behavior in IMPATT. We observed that the graphene‐SiC IMPATT is giving the better noise performance in terms of lower computed noise and noise spectral density as compared to other materials reported so far.

Influence of self-heating on the millimeter-wave and terahertz performance of MBE grown silicon IMPATT diodes

The influence of self-heating on the millimeter-wave (mm-wave) and terahertz (THz) performance of double-drift region (DDR) impact avalanche transit time (IMPATT) sources based on silicon (Si) has been investigated in this paper. The dependences of static and large-signal parameters on junction temperature are estimated using a non-sinusoidal voltage excited (NSVE) large-signal simulation technique developed by the authors, which is based on the quantum-corrected drift-diffusion (QCDD) model. Linear variations of static parameters and non-linear variations of large-signal parameters with temperature have been observed. Analytical expressions representing the temperature dependences of static and large-signal parameters of the diodes are developed using linear and 2nd degree polynomial curve fitting techniques, which will be highly useful for optimizing the thermal design of the oscillators. Finally, the simulated results are found to be in close agreement with the experimentally measured data.

Modulation of millimetre-wave and THz properties of IMPATT sources via external magnetic field

The modulation of millimetre-wave (mm-wave) and terahertz (THz) properties of impact avalanche transit time (IMPATT) sources under external steady magnetic field has been studied in this paper. The arrangement of magnetic field tuning of IMPATT oscillators by using external transverse steady magnetic field is referred to as magnetic field tunable avalanche transit time (MAGTATT) oscillators. The sensitivities of various static, large-signal and noise characteristics of silicon-based MAGTATT sources operating at mm-wave atmospheric window frequencies (94, 140 and 220 GHz) and two different THz frequencies (0.3 and 0.5 THz) have been studied. Comprehensive two-dimensional simulation models developed by the authors for evaluating static, large-signal and noise characteristics of MATATT diodes have been used for this purpose. The simulation results show that the above-mentioned magnetic field sensitivities of the device properties are significantly reduced with the increase of the operating frequency.

Numerical study of magnetic field effect on graphene based IMPATT source

Abstract Computational effect of transverse magnetic field on the performances of graphene based Impact Avalanche Transit Time (IMPATT) diode has been studied here. Detailed analysis due to magnetic field effects are presented based on a three dimensional mathematical model. Power density, dc to rf conversion efficiency, susceptance-conductance profile, drops across drift and avalanche zones are analyzed due to carrier deflections caused by magnetic field. From the computation, an upward frequency shifting of 0.1 GHz is observed due to 1 T magnetic field variation. Degradation in conversion efficiency with increment in magnetic field value has been noticed. By increasing the field effect, power density value increases. These behaviors of graphene IMPATT are in good agreement with earlier reported experimental results.

Estimation of power density in IMPATT using different materials

ABSTRACTThe RF output power dissipated per unit area is calculated using Runge-Kutta method for the high-moderate-moderate-high (n+-n-p-p+) doping profile of double drift region (DDR)-based impact avalanche transit time (IMPATT) diode by taking different substrate at Ka band. Those substrates are silicon, gallium arsenide, germanium, wurtzite gallium nitride, indium phosphide and 4H-silicon carbide. A comparative study regarding power dissipation ability by the IMPATT using different material is being presented thereby modelling the DDR IMPATT diode in a one-dimensional structure. The IMPATT based on 4H-SiC element has highest power density in the order of 1010 Wm−2 and the Si-based counterpart has lowest power density of order 106 Wm−2 throughout the Ka band. So, 4H-SiC-based IMPATT should be preferable over others for the power density preference based application. This result will be helpful to estimate the power density of the IMPATT for any doping profile and to select the proper element for the optimum design of the IMPATT as far as power density is concerned in the Ka band. Also, we have focused on variation of power density with different junction temperatures and modelled the heat sink with analysis of thermal resistances.

A new lattice-matched In0.17Al0.83N ∼ GaN based heterostructure IMPATT diode for terahertz application

Simulation studies are made on the dc and microwave performance of a novel lattice-matched In0.17Al0.83N/GaN heterostructure impact avalanche transit time (IMPATT) diode designed at the low-end terahertz frequency of 220 GHz. The electric field, breakdown voltage, rf output power and the dc-to-rf conversion efficiency of the heterostructure IMPATT diodes are compared with the GaN homostructure IMPATT diode. The results show that, a more localized avalanche region width is obtained for the heterostructure IMPATT diodes. With value of 45 nm of the In0.17Al0.83N layer width, the heterostructure IMPATT diode gives the highest efficiency (15.4%) with moderate rf output power density (1.62 MW cm−2), and the lowest Q-factor (6.57) as compared to other heterostructure and homostructure IMPATT diodes.

60 GHz Source for WLAN Applications Based on IEEE 802.11ad Protocol Standards

A high-power and low-noise 60 GHz impact avalanche transit time (IMPATT) source based on GaInAsP∼InP heterojunction has been proposed. The simulation experiments are done on InP based homojunction and two complementary heterojunction structures based on GaInAsP∼InP material system, for studying the static, large-signal and noise properties of those at 60 GHz. Results depicts that the highest RF power output with lowest noise level can be achieved at 60 GHz when N∼p junction based on Ga0.11In0.89As0.74P0.26∼InP anisotype heterojunction is grown on (100)-oriented p+-InP wafer having acceptor concentration of ∼1025 m−3. The proposed heterojunction IMPATT source is capable of delivering 4.79 W peak power with 23.21% efficiency with significantly low noise measure of only 12.5 dB; which is especially suitable for implementing 60 GHz source for ultra-high speed, short-range wireless local area network (WLAN) applications based on IEEE 802.11ad protocol standards.

Three‐Terminal Graphene Nanoribbon Tunable Avalanche Transit Time Sources for Terahertz Power Generation

Herein, the possibilities of tuning oscillation frequency and power in terahertz (THz) graphene nanoribbon (GNR)‐based avalanche transit time (ATT) sources by introducing a third terminal on their planar structure are discussed. In this regard, a three‐terminal planner impact ATT (IMPATT) structure based on GNR on oxide (SiO2) is proposed. Inherent power combining capabilities of parallel‐connected IMPATT structures are utilized to increase the power output at THz frequencies. Static, high frequency, and noise simulations are carried out using in‐house simulation codes based on self‐consistent quantum drift–diffusion model. Results show that around 0.7–5.3% and 9.0–13.3% modulation of frequency and power output are achievable, respectively, in the GNR IMPATT oscillators operating in the frequency range of 1.0–10.0 THz, respectively, by applying a suitable amount of voltage at the third or controlling terminal; however, the enhancement of noise level at the output is observed to be insignificant as a result of using the active third‐terminal control.

Modeling and computation of double drift region transit time diode performance based on graphene‐SiC

AbstractWe have proposed a double drift region (DDR) Impact Avalanche Transit Time (IMPATT) diode based on graphene‐silicon carbide (SiC) substrate. Due to attractive and extensive electronics properties of graphene materials, for the first time, we have modeled and designed the diode on epitaxially grown graphene deposited on the silicon face of SiC. The direct current (DC) characteristics and small signal performance of the modeled diode are computed with the help of COMSOL Multi Physics and MATLAB software tools. Performance is evaluated at the frequency regime of Ka band. The proposed diode is validated through the boundary conditions. Profiles of electric field distribution, density of mobile space charge, conversion efficiency, power density, susceptance‐conductance, and voltage drops at different zones are obtained. The graphene‐SiC–based DDR IMPATT is giving better DC and small signal performances.

Simulation on Large Signal and Noise Properties of (n)Si/(p)SiC Heterostructural IMPATT Diodes

Si/SiC heterostructural impact avalanche transit time (IMPATT) diode indicates of important applications in Terahertz (THz) power source, integrated circuit etc. In this paper, the (n)Si/(p)4H-SiC, (n)Si/(p)6H-SiC, (n)Si/(p)3C-SiC heterostructural double drift region IMPATT diodes operating at the atmospheric window frequency of 0.85 THz are designed by the drift-diffusion model while their static state, large signal and noise properties are numerically simulated. The performance parameters of the studied devices such as breakdown voltage, peak electric field strength, optimal negative conductance, output power, power conversion efficiency, admittance-frequency relation, quality factor, noise electric field, mean-square noise voltage per band-width and noise measure were calculated and compared. This method can guide for optimizing the Si/SiC heterostructural IMPATT device in the future.

Effect of Tunneling on Small Signal Characteristics of IMPATT Diodes with SiC Heteropolytype Structures

SiC heteropolytype structures indicate important applications in high frequency, large power solid devices etc. In this paper, the impact avalanche transit time (IMPATT) and mixed tunneling avalanche transit time (MITATT) diodes with heteropolytype consisting of two semiconductors among the 3C-SiC, 4H-SiC and 6H-SiC are numerically simulated to investigate the static state and small signal characteristics at the atmospheric window frequency of 1.56 THz. The breakdown voltage, avalanche voltage, peak value of static electric field, the maximum generation rates of avalanche and tunneling, power conversion efficiency, admittance-frequency relation of the proposed SiC heteropolytype diodes are calculated, respectively. Comparing the obtained parameters of IMPATT diodes with those of MITATT devices, the results imply that tunneling shows little influence on the small signal performance of the heteropolytype IMPATT diodes included 3C-SiC material, which is different from those of the homopolytype counterparts.

1.0–10.0 THz Radiation from Graphene Nanoribbon Based Avalanche Transit Time Sources

The possibilities of terahertz frequency generation by using graphene nanoribbon (GNR) based avalanche transit time (ATT) sources are investigated in this paper. The most promising candidate of ATT device family, i.e., the impact avalanche transit time (IMPATT) diode is chosen for the present study. Parallel connected GNR based IMPATT structures with inherent power combining capability are proposed and simulated by using self‐consistent quantum drift‐diffusion model based in‐house simulation codes in order to study the static, high frequency and noise performance of those at different millimeter‐wave and terahertz frequency bands. The detailed study reveals that the in‐build power combined GNR IMPATT sources are capable of performing more efficiently than the IMPATT sources based on some other popular semiconductor materials as well as some state‐of‐the‐art terahertz radiators within the terahertz frequency band from 1 to 10 THz.

Quantum corrected drift diffusion based noise model for impact avalanche and transit time diode

We have proposed a quantum corrected drift diffusion based noise model for the more accurate noise computation of double drift region Impact Avalanche Transit Time diode, operating from 26.5 GHz to 40 GHz. Measuring of noise in IMPATT is very difficult task as the noise arises from the generation of electron and hole pairs, due to major effects like hot carriers transport in semiconductor, phonon scattering, inter band scattering of electrons and holes, quantum confinement, quantum tunneling. Conventional classical drift diffusion noise model is independent of these effects. However, in this paper a quantum corrected noise model has been presented in addition to the classical drift diffusion noise model by considering the quantum effects. For the validation of the proposed noise model, silicon has considered as the base material of IMPATT diode. The results obtained from the proposed model are in good agreement with the experimentally measured noise performance and giving better response as compared to that of classical noise model.

Noise performance of avalanche transit-time devices in the presence of acoustic phonons

Through this paper, the effects of acoustic phonons on the noise performance of avalanche transit-time devices have been investigated and reported. For this study, a double-drift-region silicon-based impact avalanche transit-time diode has been considered at operating frequencies of 94 GHz, 140 GHz and 220 GHz. To analyze the acoustic phonon effects on noise performance, the interactions of charge carriers with acoustic deformation potential and piezoelectric acoustic phonons have been considered in addition to all possible types of scattering events. These effects have been analyzed through a numerical expression for the ionization rate of charge carriers and incorporated in the noise analysis. The noise performance is evaluated in terms of noise spectral density (NSD) and noise measure (NM). The results show that due to acoustic phonons, values of NSD and NM significantly increase.