In this paper large-signal modeling and simulation has been carried to study the frequency chirping due to temperature transients and the large-signal power and efficiency of pulsed silicon Double-Drift Region (DDR) Impact Avalanche Transit Time (IMPATT) device operating at 94 GHz. A large-signal simulation method based on non-sinusoidal voltage excitation incorporating the transient thermal effect has been developed by the authors. Results show that the device is capable of delivering a peak pulsed power output of 17.5 W with 12.8% efficiency when the voltage modulation is 60%. The maximum junction temperature rise is 350.2 K for a peak pulsed bias current of 6.79 A with 100 ns pulsewidth and 0.5 percent duty cycle; whereas the chirp bandwidth is 8.3 GHz.

Large-Signal Simulation of 94 GHz Pulsed Silicon DDR IMPATTs Including the Temperature Transient Effect

A major amount of energy of mobile electrons and holes in a semiconductor under electric field are lost due to inter-carrier collisions prior to ionising collision. This fact causes a decrease in the ionisation probability which leads to the deterioration in ionisation rates especially when the doping density is high. The effects of this phenomenon on the high frequency and noise properties of highly doped impact avalanche transit time (IMPATT) devices based on different wide bandgap (WBG) semiconductors, like 4H-SiC, Wurtzite-GaN (Wz-GaN) and type-IIb diamond (C) have been studied in this paper. Significant deteriorations in the diodes' high frequency and noise performance have been observed in the simulation results. The simulation results have been compared with the experimental data in order to validate those.

Millimetre-wave and terahertz IMPATT sources: influence of inter-carrier interactions

Negative resistivity of Si and Si0.9Ge0.1 DDR IMPATT diode are numerically computed using double iterative method and modified Runge-Kutta method and results are compared for identical input parameters. Simulation is based on simultaneous solution of Poisson's equation, continuity equation and carrier diffusion equation in addition with the effect of mobile space charge subject to the appropriate boundary conditions at the edges of depletion layer. Effect of junction temperature and current density on resistance is evaluated for optimum performance in CE mode. Peaks of the resistivity profile depend on temperature, bias current and frequency of operation. Results suggest that Si0.9Ge0.1 shows more negative resistance than the conventional one, and thus it may be considered as the suitable alternative choice for microwave source.

Dependence of Negative Resistivity on Current Density and Junction Temperature for DDR IMPATT

The potentiality of millimter-wave (mm-wave) double-drift region (DDR) impact avalanche transit time (IMPATT) diodes based on a wide bandgap (WBG) semiconductor material, Gallium Phosphide (GaP) has been explored in this paper. A nonsinusoidal voltage excited (NSVE) large-signal simulation method has been used to study the DC and high frequency characteristics of DDR GaP IMPATTs dsigned to operate at mm-wave atmospheric window frequencies such as 94, 140 and 220 GHz. Results show that the DDR GaP IMPATTs are capable of delivering significantly higher RF power at the above mentioned window frequencies as compared to the DDR IMPATTs based on the conventional narrow bandgap (NBG) base materials such as Si, GaAs and InP.

Gallium Phosphide IMPATT Sources for Millimeter-Wave Applications

Influences of magnetic field on the noise performance of double-drift region (DDR) impact avalanche transit time (IMPATT) device based on Si designed to operate within W-band (75–110 GHz) have been studied in this paper. The reverse biased DDR IMPATT structure under transverse magnetic field can be regarded as magnetic field tunable avalanche transit time (MAGTATT) device. The simulation results show that both the noise spectral density and noise measure of the device increase significantly while the device is kept in transverse magnetic field. This degradation of the noise performance of the device enhances when the magnitude of the magnetic field is increased. Therefore, in order to achieve the magnetic field tuning of the RF properties of DDR IMPATTs as reported earlier by the authors, the noise performance of the source has to be sacrificed in fair extent.

Avalanche noise in magnetic field tunable 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 Olson's 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.

Apc Road

Papers

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