Impact Avalanche Transit Time Diodes 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 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.

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.

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.

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.

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.

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.

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.

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.

Prospects of Impact Avalanche Transit-Time Diode Based on Chemical-Vapor-Deposited Diamond Substrate

We propose a chemical-vapor-deposited (CVD) diamond-based double-drift-region (DDR) impact avalanche transit-time diode (IMPATT) for use in microwave applications. CVD diamond is taken as the base substrate material. Simulations were carried out to perform direct-current (DC), small-signal, and noise analyses on the IMPATT. The results are in agreement with experimental reports. The IMPATT based on CVD diamond offers better performance compared with other materials reported to date at 26 GHz to 40 GHz. In the near future, this device could represent the best alternative for designers and semiconductor industry, due to its numerous advantages including higher DC-to-radiofrequency (RF) conversion efficiency (27.81%), highest power density (6.206 × 109 W m−2), minimum noise value (− 98.22 dBm), and best optimized conductance–susceptance profile with lower quality factor (0.0215).

1.0 THz GaN IMPATT Source: Effect of Parasitic Series Resistance

The degradation of high-frequency characteristics of a 1.0-THz double-drift region (DDR) impact avalanche transit time (IMPATT) diode based on wurtzite gallium nitride (Wz-GaN), due to the influence of parasitic series resistance, has been investigated. A two-dimensional (2-D) large-signal (L-S) simulation method based on a non-sinusoidal voltage excitation (NSVE) model has been used for this purpose. A comprehensive model of series resistance has been developed by considering the influence of skin effect, and the said model has been incorporated in the 2-D L-S simulation for studying the effect of RF power output and DC to RF conversion efficiency of the device. Results indicate 24.2–35.9% reduction in power output and efficiency due to the RF power dissipation in the positive series resistance. However, the device can still deliver 191.7–202.9 mW peak RF power to the load at 1.0 THz with 8.48–6.41% conversion efficiency. GaN IMPATT diodes are capable of generating higher RF power at around 1 THz than conventional diodes, but the effect of parasitic series resistance causes havoc reduction in power output and efficiency. The nature of the parasitic resistance is studied here in the level of device fabrication and optimization, which to our knowledge is not available at present.

Influence of Carrier–Carrier Interactions on the Noise Performance of Millimeter-Wave IMPATTs

ABSTRACTThe influence of inter-carrier scattering phenomena on the noise performance of double-drift region (DDR) impact avalanche transit time diodes has been investigated. Three optimized Si DDR diode structures operating at 94, 140 and 220 GHz have been taken into account for this study. A newly reported analytical model of the ionization rates has been incorporated in the simulation in order to consider the effect of inter-carrier scattering inside the active region of the diodes and the noise performance of those have been evaluated by calculating the noise spectral density and noise measure around respective operating frequency bands. Results show that the noise performances of those are drastically worsened due to the aforementioned effect. The said deterioration has been found to be monotonically increasing in nature with the working frequency.

Self-consistent quantum drift-diffusion model for multiple quantum well IMPATT diodes

In this paper, the authors have presented a self-consistent quantum drift-diffusion model for multiple quantum well (MQW) impact avalanche transit time (IMPATT) diodes. The bound states in MQWs have been taken into account by self-consistent solutions of the coupled classical drift-diffusion (CLDD) equations and time-independent Schrodinger equations associated with both the conduction and valence bands. The static and high-frequency properties of MQW DDR IMPATTs based on Si$$\sim $$~3C-SiC material system designed to operate near 94-GHz atmospheric window have been studied by means of the above-mentioned self-consistent solutions of coupled CLDD equations and Schrodinger equations followed by a well-established double-iterative field maximum computational technique. A symmetric and two complementary asymmetric doping profiles for the proposed structures have been taken into account for the present study. The RF power outputs of Si$$\sim $$~3C-SiC MQW DDR IMPATTs near 94 GHz obtained from the simulation are compared with the experimentally obtained power outputs of flat DDR IMPATT diodes based on Si, GaAs, and InP at the same frequency band. It is observed that Si$$\sim $$~3C-SiC MQW DDR IMPATTs are capable of delivering significantly higher RF power compared with IMPATTs based on the above-mentioned materials especially when the doping concentrations of 3C-SiC layers are kept higher than those of the Si layers.

Effect of temperature on avalanche region width and DC to RF conversion efficiency of the p+nn−n+ 4H–SiC impact avalanche transit time diodes

The effect of temperature on avalanche region width and DC to RF conversion efficiency of the p+nn−n+ impact ionization avalanche transit time diodes based on 4H–SiC material for 140 GHz design frequency has been investigated by means of the MEDICI simulation platform. It is shown that the avalanche region width of the IMPATT diodes working at the same operating current densities first decreases and then increases with the increasing temperature. The DC to RF conversion efficiency of the IMPATT diodes first increases and then decreases with the increasing temperature. The increase in ionization rate of impurities with increasing temperature and the decrease in the carrier impact ionization rate with increasing temperature are responsible for the results. In addition, the expansion of avalanche region and the degradation of DC to RF conversion efficiency at lower temperature are more pronounced in lower p+ region doping concentration diode than that in higher p+ region doping concentration.

Heterojunction DDR THz IMPATT diodes based on AlxGa1−xN/GaN material system

Simulation studies are made on the large-signal RF performance and avalanche noise properties of heterojunction double-drift region (DDR) impact avalanche transit time (IMPATT) diodes based on AlxGa1−xN/GaN material system designed to operate at 1.0 THz frequency. Two different heterojunction DDR structures such as n-Al0.4Ga0.6N/p-GaN and n-GaN/p-Al0.4Ga0.6N are proposed in this study. The large-signal output power, conversion efficiency and noise properties of the heterojunction DDR IMPATTs are compared with homojunction DDR IMPATT devices based on GaN and Al0.4Ga0.6N. The results show that the n-Al0.4Ga0.6N/p-GaN heterojunction DDR device not only surpasses the n-GaN/p-Al0.4Ga0.6N DDR device but also homojunction DDR IMPATTs based on GaN and Al0.4Ga0.6N as regards large-signal conversion efficiency, power output and avalanche noise performance at 1.0 THz.

IMPATT Diodes Based on 〈111〉, 〈100〉, and 〈110〉 Oriented GaAs: A Comparative Study to Search the Best Orientation for Millimeter-Wave Atmospheric Windows.

The authors have carried out the large-signal (L-S) simulation of double-drift region (DDR) impact avalanche transit time (IMPATT) diodes based on 〈111〉, 〈100〉, and 〈110〉 oriented GaAs. A nonsinusoidal voltage excited (NSVE) L-S simulation technique is used to investigate both the static and L-S performance of the above-mentioned devices designed to operate at millimeter-wave (mm-wave) atmospheric window frequencies, such as 35, 94, 140, and 220 GHz. Results show that 〈111〉 oriented GaAs diodes are capable of delivering maximum RF power with highest DC to RF conversion efficiency up to 94 GHz; however, the L-S performance of 〈110〉 oriented GaAs diodes exceeds their other counterparts while the frequency of operation increases above 94 GHz. The results presented in this paper will be helpful for the future experimentalists to choose the GaAs substrate of appropriate orientation to fabricate DDR GaAs IMPATT diodes at mm-wave frequencies.