Pulsed IMPATT Diodes Research Articles

Models for IMPATT Diode Analysis and Optimization

Some of nonlinear models for high-power pulsed IMPATT diode simulation and analysis is presented. These models are suitable for the analysis of the different operational modes of the oscillator. Its take into account the main electric and thermal phenomena in the semiconductor structure and the functional dependence of the equation coefficients on the electrical field and temperature. The first model is a precise one, which describes all important electrical phenomena on the basis of the continuity equations and Poisson equation and it is correct until 300 GHz. The second approximate mathematical model suitable for the analysis of IMPATT diode stationary operation oscillator and for optimization of internal structure of the diode. This model is based on the continuity equation system solution by reducing the boundary problem for the differential partial equations to a system of the ordinary differential equations. The temperature distribution in the semiconductor structure is obtained using the special thermal model of the IMPATT diode, which is based on the numerical solution of the non-linear thermal conductivity equation. The described models can be applied for analysis, optimization and practical design of pulsed-mode millimetric IMPATT diodes. Its can be also utilized for diode thermal regime estimation, for the proper selection of feed-pulse shape and amplitude, and for the development of the different type of complex doping-profile high-power pulsed millimetric IMPATT diodes with improved characteristics.

Analysis of Electrical and Thermal Models for Pulsed IMPATT Diode Simulation

Some nonlinear models are presented for modeling and analyzing IMPATT high-power pulse diodes. These models are suitable for analyzing different operating modes of the oscillator. The first model is a precise one, which describes all important electrical phenomena on the basis of the continuity equations and Poisson´s equation, and it is correct until 300 GHz. The second approximate mathematical model suitable for the analysis of IMPATT diode stationary operation oscillator and for optimization of internal structure of the diode. The temperature distribution in the semiconductor structure is obtained using the special thermal model of the IMPATT diode, which is based on the numerical solution of the non-linear thermal conductivity equation. The described models can be applied for the analysis, optimization and practical design of pulsedmode millimetric IMPATT diodes. It can also be used to evaluate the thermal behavior of diodes, to correctly select the shape and amplitude of a supply pulse, and to design various types of high-power pulsed millimeter IMPATT diodes with a complex doping profile with improved characteristics.

Chirp Band-Width Estimation of MM-Wave Pulsed-MPATT: A Study on the Dependence of Device Diameter and Bias Pulse-Width

In this work, the authors have studied the dependence of chirp bandwidth viz. intra pulse change in frequency on the bias pulse width and on the diode junction diameter of pulsed IMPATT diodes. Using a small signal simulation model and a suitable thermal model, intra pulse diode susceptance are computed and from the sustained oscillation condition, the circuit susceptance presented at the device terminal is calculated and frequency chirp bandwidth is estimated. The results are presented in details and would be useful for design optimization of pulsed IMPATTs at Wband.

Active layer parameter optimization for high-power Si 2 mm pulsed IMPATT diode

On the basis of an IMPATT diode complex mathematical model and an optimization procedure, results are presented for a diode structure analysis and optimization suitable for a pulsed-mode 2 mm silicon diode. The energy characteristics of the semiconductor structures for high-power pulsed IMPATT diodes with a permanent and complex doping profile are optimized. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 4–9, 1998.

Computer Studies on Pulsed Silicon MM-Wave IMPATT Diodes for various DDR Structures at High Current Density

A review of the pulsed mode high power generation in silicon DDR IMPATT devices at high current density has been presented together with the current work of the authors in the same subject.Computer studies have been presented on silicon pulsed IMPATT diodes with various double drift region (DDR) structures for operation at 94 GHz at a current density of 100 KA/cm2. Three structures: (i) flat, (ii) SLHL, i.e., low-high-low structure with single bump on either side of the p-n junction and (iii) DLHL, i.e., low-high-low structures with double bumps on either side of the p-n junction have been investigated. The dc & small-signal results indicate that suitably designed silicon DDR IMPATT devices with double impurity bumps on either side of the junction exhibit much higher negative conductance and power output than other structures.It is seen that appropriately designed DDR structures could be operated at a high current density of 100 KA/cm2, with narrow avalanche zone to give sufficient W-band pulsed power, while several investigators have earlier suggested that the pulsed high power operation could be due to uniformly avalanching pin mode.

Unequal space charge region widths and deviation of avalanche region centre in symmetrical pulsed double-drift IMPATT diode

Unequal space charge region widths on the p and n sides of a symmetrical double drift Si IMPATT diode are observed under pulsed operating conditions. The space charge region width on the p side is greater than its value on the n side and the difference is appreciable at higher current densities. This unusual behaviour in a symmetrical structure is attributed to the carrier's space-charge effect. Moreover, the deviation of the avalanche region centre from the p-n junction interface is not significant at mm-wave frequencies, as commonly believed. The inequality in space charge region widths in symmetrical structure starts in the range of current levels where the conventional design mode is valid. It thus violates conventional design criteria and reduces the diode's Q and efficiency. An optimisation method for improved performance of pulsed IMPATT diodes in the conventional design mode is presented and shown by extending Chang and Ebert's symmetrical optimum design for 10–15 W pulsed power at 94 GHz.

Double Diode Pulsed Impatt Resonant Cavity Combiner at Ka Band

A 34 Watt dual diode pulsed Impatt cavity combiner has been developed at 35 GHz with 100 ns pulse width and 100 kHz PRF using two single pulsed Impatt diodes of 16 Watt each. The total output power of the combiner is slightly greater that the sum of the output powers produced from individual Impatts (as quoted in the catalogue) giving a combining efficiency slightly greater than 100 percent. To achieve this remarkable efficiency, selection of diodes is very critical and a practical technique called ‘delay technique’ was found very useful in selecting suitable diodes for optimisation of the combiner.

Physical understanding and optimum design of high-power millimeter-wave pulsed IMPATT diodes

A physical understanding of the specific mode of operation of high-power millimeter-wave pulsed IMPATT diodes is derived from a self-consistent numerical model. It is shown theoretically that there exists a uniformly avalanching p-i-n-like mode in high-current-density, pulsed silicon double-drift IMPATT diodes, as has been previously suggested. An optimum symmetrical flat doping-profile double-drift structure for 100-GHz operation is presented. It could deliver more than 40 W of available peak power with a 10% conversion efficiency accounting for circuit losses, at a safe junction temperature rise. The theoretical results allow an optimum design of the 94-GHz IMPATT structure for peak output power in excess of 50 W under low duty cycle.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-power operation mode of pulsed IMPATT diodes

Pulsed silicon double-drift IMPATT diodes that yield 42 W at 96 GHz are discussed. This is about twice the value reported previously. Owing to the considerable input powers ( approximately=500 W), these diodes are mounted on diamond heat sinks. Because of the strong carrier injection, the field distribution in the diode is similar to that in a p-i-n diode. An attempt is made to explain the results using T. Misawa's (1966) p-i-n type theory. The large-signal; avalanche resonant frequency is close to the operation frequency. Conventional Read-type theory fails to explain these results because of the current densities employed in the experiments. >

Frequency chirp in W-band pulsed IMPATT oscillators

An analytical device-circuit interaction model to compute the frequency chirp bandwidth in W-band pulsed DDR IMPATT diodes is presented. The measured chirp agrees reasonably well with the calculated values.

Power Increase of Pulsed Millimeter-Wave IMPATT Diodes (Short Paper)

The fabrication and encapsulation of single-drift pulsed IMPATT diodes for 73 GHz is described. The transforming properties of the parasitic inductance and capacitance demonstrate the strong influence of diode-mounting technique. The used reduced-height waveguide resonator is described theoretically, giving an indication of optimum matching between resonator and transformed diode impedance. The diodes deliver more than 10-W output power at 73 GHz with 5-percent efficiency, if they are matched to the resonator by proper parasitic.

High-power pulsed beam-lead IMPATT diodes for millimetre waves

IMPATT diodes with technologically integrated beam-leads were fabricated. Since no diode bonding is required, a total diode thickness of less than 2 μm can be realised reproducibly. With optimum device packages, peak pulse output powers of more than 10 W at 70 GHz have been achieved from silicon single-drift IMPATT diodes.

Transient temperature behavior in pulsed double-drift IMPATT diodes

The temperatures in a pulsed double-drift IMPATT diode are calculated as a function of position and time by a finite difference calculation using the alternating direction algorithm. The results are given as a function of pulse length and duty factor for a typical double-drift diode designed to operate near X band. Techniques are described for choosing spatial meshes and time integrals which vary with position and time in a way that minimizes computation time. Numerical results are chosen to illustrate the distribution of temperature within the diode at different times during the pulse, the effect of a temperature-dependent breakdown voltage upon radial temperature distribution, and the interplay between the short thermal-diffusion times within the GaAs diode and the long times associated with the slow heating-up of the heat sink at great distances. An extended definition of thermal resistance for pulsed diodes is introduced and the implications upon reliability are discussed.

Two-diode power combining near 140 GHz

This letter describes the achievement of 3.0 W peak power output near 145.0 GHz by combining two pulsed Impatt diodes in a resonant waveguide cavity. A combining efficiency of close to 90% was obtained.

High-power pulsed GaAs double-drift hybrid-read impatt diodes for X-band

Gallium-arsenide double-drift hybrid-Read Impatt diodes have been developed to deliver high peak and average powers in X-band. A peak power output of 35 W with 20% efficiency has been obtained at 8.3 GHz for 20% duty cycle. Peak power output of 32 W with 20% efficiency has been obtained at 8·6 GHz for a 25% duty cycle. Peak power output of 26 W with 21.5% efficiency has been obtained at 8.6. GHz for 33% duty cycle.

Millimeter-wave pulsed IMPATT diode oscillators

Double-drift silicon IMPATT diodes were fabricated for pulse source application at 35, 94, and 140 GHz. The diodes were operated with 300 ns pulsewidth and a 1.5 percent duty cycle. All sources exhibited a change in output frequency of >1 percent throughout the duration of the pulsewidth with <1 dB peak power variation. Peak pulse output power levels of 10, 2, and 0.7 W were achieved in each of the three frequency bands, respectively.