Suranjana Banerjee

Effect of junction temperature on the large-signal properties of a 94 GHz silicon based double-drift region impact avalanche transit time device

The authors have developed a large-signal simulation technique extending an in-house small-signal simulation code for analyzing a 94 GHz double-drift region impact avalanche transit time device based on silicon with a non-sinusoidal voltage excitation and studied the effect of junction temperature between 300 and 550 K on the large-signal characteristics of the device for both continuous wave (CW) and pulsed modes of operation. Results show that the large-signal RF power output of the device in both CW and pulsed modes increases with the increase of voltage modulation factor up to 60%, but decreases sharply with further increase of voltage modulation factor for a particular junction temperature; while the same parameter increases with the increase of junction temperature for a particular voltage modulation factor. Heat sinks made of copper and type-IIA diamond are designed to carry out the steady-state and transient thermal analysis of the device operating in CW and pulsed modes respectively. Authors have adopted Olsons method to carry out the transient analysis of the device, which clearly establishes the superiority of type-IIA diamond over copper as the heat sink material of the device from the standpoint of the undesirable effect of frequency chirping due to thermal transients in the pulsed mode.

Large-signal characterization of DDR silicon IMPATTs operating in millimeter-wave and terahertz regime

The authors have carried out the large-signal characterization of silicon-based double-drift region (DDR) impact avalanche transit time (IMPATT) devices designed to operate up to 0.5 THz using a large-signal simulation method developed by the authors based on non-sinusoidal voltage excitation. The effect of band-to-band tunneling as well as parasitic series resistance on the large-signal properties of DDR Si IMPATTs have also been studied at different mm-wave and THz frequencies. Large-signal simulation results show that DDR Si IMPATT is capable of delivering peak RF power of 633.69 mW with 7.95% conversion efficiency at 94 GHz for 50% voltage modulation, whereas peak RF power output and efficiency fall to 81.08 mW and 2.01% respectively at 0.5 THz for same voltage modulation. The simulation results are compared with the experimental results and are found to be in close agreement.

Potentiality of semiconducting diamond as the base material of millimeter-wave and terahertz IMPATT devices

An attempt is made in this paper to explore the potentiality of semiconducting type-IIb diamond as the base material of double-drift region (DDR) impact avalanche transit time (IMPATT) devices operating at both millimetre-wave (mm-wave) and terahertz (THz) frequencies. A rigorous large-signal (L-S) simulation based on the non-sinusoidal voltage excitation (NSVE) model developed earlier by the authors is used in this study. At first, a simulation study based on avalanche response time reveals that the upper cut-off frequency for DDR diamond IMPATTs is 1.5 THz, while the same for conventional DDR Si IMPATTs is much smaller, i.e. 0.5 THz. The L-S simulation results show that the DDR diamond IMPATT device delivers a peak RF power of 7.79 W with an 18.17% conversion efficiency at 94 GHz; while at 1.5 THz, the peak power output and conversion efficiency decrease to 6.19 mW and 8.17% respectively, taking 50% voltage modulation. A comparative study of DDR IMPATTs based on diamond and Si shows that the former excels over the later as regards high frequency and high power performance at both mm-wave and THz frequency bands. The effect of band to band tunneling on the L-S properties of DDR diamond and Si IMPATTs has also been studied at different mm-wave and THz frequencies.

Effect of photo-irradiation on the noise properties of double-drift silicon MITATT device

In this paper, the authors have made an attempt to study the effect of photo-irradiation on the avalanche noise properties of double-drift region (DDR) mixed tunnelling and avalanche transit time (MITATT) device. A model to analyse the avalanche noise of illuminated DDR MITATT devices under small-signal condition is proposed and simulation is carried out to study the noise properties of the device based on silicon designed to operate at W-band. The results show that avalanche noise measure of the device under two different optical illumination configurations such as Flip Chip (FC) and Top Mount (TM) are 37.1 dB and 40.2 dB, respectively, for the incident photon flux density of 1026 m−2 sec−1 at 1000 nm wavelength while the noise measure of the same device under dark condition is 35 dB. Thus, the increase of avalanche noise due to the incident photon flux on optically illuminated device can be reduced if FC configuration is taken instead of TM configuration.

Noise Performance of Heterojunction DDR MITATT Devices Based on at W-Band

Noise performance of different structures of anisotype heterojunction double-drift region (DDR) mixed tunneling and avalanche transit time (MITATT) devices has been studied. The devices are designed for operation at millimeter-wave W-band frequencies. A simulation model has been developed to study the noise spectral density and noise measure of the device. Two different mole fractions and of Ge and corresponding four types of device structure are considered for the simulation. The results show that the -Si heterojunction DDR structure of MITATT device excels all other structures as regards noise spectral density ( sec) and noise measure (33.09 dB) as well as millimeter-wave properties such as DC-to-RF conversion efficiency (20.15%) and CW power output (773.29 mW).

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 Al x Ga 1-x N/GaN material system designed to operate at 1.0 THz frequency. Two different heterojunction DDR structures such as n-Al 0.4 Ga 0.6 N/p-GaN and n-GaN/p-Al 0.4 Ga 0.6 N 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 Al 0.4 Ga 0.6 N. The results show that the n-Al 0.4 Ga 0.6 N/p-GaN heterojunction DDR device not only surpasses the n-GaN/p-Al 0.4 Ga 0.6 N DDR device but also homojunction DDR IMPATTs based on GaN and Al 0.4 Ga 0.6 N as regards large-signal conversion efficiency, power output and avalanche noise performance at 1.0 THz.

A proposed method to study the parasitic resistance of Ka-band Silicon IMPATT diode from large-signal electric field snap-shots

In this paper a novel method based on the concept of time varying depletion width modulation at large-signal levels is proposed to obtain the parasitic resistance of the inactive region of Ka-band Silicon Single-Drift Region (SDR) Impact Avalanche Transit Time (IMPATT) diodes. A complete simulation software based on non-sinusoidal voltage excitation method is developed to obtain the large-signal electric field snap-shots of the device at different bias current densities and different phase angles of a full cycle of steady-state oscillation from which the parasitic series resistance of the device is calculated. The series resistance is also calculated from the conventional method i.e., from the large-signal admittance characteristics at threshold frequency. The results however show that the proposed method to determine the series resistance provides better and closer agreement with the experimentally reported value than the conventional method.

Large signal and noise properties of heterojunction Al x Ga1−x As/GaAs DDR IMPATTs

Simulation studies are carried out on the large signal and noise properties of heterojunction (HT) Al x Ga 1- x As/GaAs double drift region (DDR) IMPATT devices at V-band (60 GHz). The dependence of Al mole fraction on the aforementioned properties of the device has been investigated. A full simulation software package has been indigenously developed for this purpose. The large signal simulation is based on a non-sinusoidal voltage excitation model. Three mole fractions of Al and two complementary HT DDR structures for each mole fraction i.e., six DDR structures are considered in this study. The purpose is to discover the most suitable structure and corresponding mole fraction at which high power, high efficiency and low noise are obtained from the device. The noise spectral density and noise measure of all six HT DDR structures are obtained from a noise model and simulation method. Similar studies are carried out on homojunction (HM) DDR GaAs IMPATTs at 60 GHz to compare their RF properties with those of HT DDR devices. The results show that the HT DDR device based on N-Al x Ga 1- x As/p-GaAs with 30% mole fraction of Al is the best one so far as large signal power output, DC to RF conversion efficiency and noise level are concerned.

94 GHz multiquantum well IMPATT diodes based on 3C-SiC/Si material system

A multiquantum well (MQW) double-drift region (DDR) impact avalanche transit time (IMPATT) device based on Si/3C-SiC material system has been proposed for high frequency application. One symmetrical and two asymmetrical doping profiles for the proposed hetero-structure device are considered in the present study. The design and optimization of the above-mentioned three doping profiles of Si/3C-SiC MQW hetero-structure DDR IMPATT diodes have been carried out by simulation technique so that the device operates at millimeter wave W-band (75-100 GHz) frequencies. The DC and large signal properties of the device are obtained from a large signal simulation program based on non-sinusoidal voltage excited model in which the density gradient theory and Böhm Potential are incorporated to provide a quantum equivalent of drift-diffusion model. The RF output power of the proposed MQW DDR IMPATTs operating at and near 94 GHz atmospheric window frequency are obtained from the simulation output and compared with the available reported values of output power for flat profile DDR IMPATT diodes at the same frequency band. The results show that among the three doping profiles of Si/3C-SiC MQW DDR IMPATT device, the asymmetrical one with higher n and p type doping concentrations of Silicon layers as compared to those of SiC layers is the preferred doping profile for better RF performance at W-band.

Design optimization and large-signal simulation of DLHL Si IMPATT diode at 60 GHz

A four-level optimization technique has been used to design a double low-high-low (DLHL) impact avalanche transit time (IMPATT) diode based on Si for 60 GHz operation. Initially the position of the charge bumps in both n- and p-epitaxial layers followed by the widths of those and the ratio of high to low doping concentrations have been varied subject to obtain the maximum large-signal DC to RF conversation efficiency from the device. Finally the bias current density is varied within a specified range to obtain the optimum value of it for which the DC to RF conversation efficiency of the device is maximum. The above mentioned four optimization steps have been repeated until the method converges to provide a stable optimized DC to RF conversion efficiency. A large-signal simulation technique based on non-sinusoidal voltage excitation (NSVE) model developed by the authors is used for this purpose. The large-signal properties of the optimized DLHL Si IMPATT have been simulated and those are compared with the experimental results reported earlier. The said comparison shows that the optimized DLHL diode is capable of delivering significantly higher RF power output with greater DC to RF conversion efficiency at 60 GHz as compared to its un-optimized counterpart.