Design and optimization of Schottky varactor diode frequency multipliers for millimeter and submillimeter wavelengths are generally performed using harmonic balance techniques together with equivalent-circuit models. Using this approach, it is difficult to design and optimize the device and multiplier circuit simultaneously. The work presented in this paper avoids the need of equivalent circuits by integrating a numerical simulator for Schottky diodes into a circuit simulator. The good agreement between the calculated and published experimental data for the output power and conversion efficiency originates from the accurate physical model. The limiting effects of multiplier performance such as breakdown, forward conduction, or saturation velocity are discussed in view of the optimum circuit conditions for multiplier operation including bias point, input power, and loads at different harmonics. It is shown that the onset of forward or reverse current flow is responsible for the limitation in the conversion efficiency.

Modeling and design aspects of millimeter-wave and submillimeter-wave Schottky diode varactor frequency multipliers

A microscopic analysis of current and voltage fluctuations in GaAs Schottky barrier diodes under forward-bias conditions in the absence of 1/f contributions is presented. Calculations are performed by coupling self-consistently an ensemble Monte Carlo simulator with a one-dimensional Poisson solver. By using current- and voltage-operation modes the microscopic origin and the spatial location of the noise sources, respectively, is provided. At different voltages the device exhibits different types of noise (shot, thermal, and excess), which are explained as a result of the coupling between fluctuations in carrier velocity and self-consistent field. The essential role of the field fluctuations to correctly determine the noise properties in these diodes is demonstrated. The results obtained for the equivalent noise temperature are found to reproduce the typical behavior of experimental measurements. An equivalent circuit is proposed to predict and explain the noise spectra of the device under thermionic emis...

Microscopic analysis of electron noise in GaAs Schottky barrier diodes

An efficient one-dimensional ensemble Monte Carlo simulator that improves the study of carrier transport by including a space-variable charge algorithm has been developed. The algorithm is automatically implemented in regions with remarkable concentration gradients. In this way is possible to study devices in which the carrier concentration varies by several orders of magnitude along the device and/or when we are interested in the population of states rarely occupied by the carriers (tails of distribution functions, hot electrons, etc) without excessive CPU requirements. In the present work this technique is used to study a Schottky barrier diode over a wide range of forward bias (80 - 800 mV). In particular, the exponential behaviour of the current - voltage characteristic, the agreement of this with the experimental results, the distribution function and the recombination velocity of carriers close to the metal - semiconductor interface confirm the validity of the implemented algorithm.

Monte Carlo analysis of a Schottky diode with an automatic space-variable charge algorithm

A high power doubler for the frequency band 184 to 212 GHz has been fabricated and tested The results of the continuing JPL Schottky diode physical modeling effort are discussed, including the effects of temperature and high power operation

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A high-power wideband cryogenic 200 GHz schottky substrateless multiplier: modeling, design and results

Substantial proress has been made recently in the advancement of solid state terahertz sources using chains of Schottky diode frequency multipliers We have developed a harmonic balance simulator and corresponding diode model that incorporates many other factors participating in the diode behavior

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Harmonic balance optimization of terahertz Schottky diode multipliers using an advanced device model

A numerical model resulting in the current-voltage characteristics of standard and heteroepitaxial Schottky-barrier diodes is presented. Simulations of GaAs diodes, as well as InGaAs diodes grown on GaAs and InP substrates, are presented. The model considers quantum-mechanical tunneling, and is therefore applicable to highly doped devices. A self-consistent drifted-Maxwellian distribution is used to model the electron energy distribution at high current densities. The assumption of a drifted-Maxwellian distribution is shown to lead to higher current at high bias than predicted with the assumption of a Maxwell-Boltzmann or Fermi-Dirac distribution. The presence of a heterojunction at the InGaAs-substrate interface is predicted to lead to an additional series resistance component. >

U.V. Bhapkar

Papers

Numerical simulation of the current-voltage characteristics of heteroepitaxial Schottky-barrier diodes