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Progress on Single Barrier Varactors for Submillimeter Wave Power Generation

Authors:
Svein M. Nilsen, Hans Grönqvist, Hans Hjelmgren, Anders Rydberg, Erik Kollberg
Abstract:
Theoretical work on Single Barrier Varactor (SEW) diodes, indicate that the efficiency for a multiplier has a maximum for a considerably smaller capacitance variation than previously thought. The theoretical calculations are performed, both with a simple theoretical model and a complete computer simulation using the method of harmonic balance. Modelling of the SBV is carried out in two steps. First, the semiconductor transport equations are solved simultaneously using a finite difference scheme in one dimension. Secondly, the calculated IV-, and CV characteristics are input to a multiplier simulator which calculates the optimum impedances, and output powers at the frequencies of interest. Multiple bather varactors can also be modelled in this way. Several examples on how to design the semiconductor layers to obtain certain characteristics are given The calculated conversion efficiencies of the modelled structures, in a multiplier circuit, are also presented. Computer simulations for a case study of a 750 GHz multiplier show that InAs diodes perform favourably compared to GaAs diodes. InAs and InGaAs SBV diodes have been fabricated and their current vs. voltage characteristics are presented. In the InAs diode, was the large bandgap semiconductor AlSb used as barrier. The InGaAs diode was grown lattice matched to an InP substrate with InAlAs as a barrier material. The current density is greatly reduced for these two material combinations, compared to that of GaAs/AlGaAs SBV diodes. GaAs based diodes can be biased to higher voltages than InAs diodes.
Categories:
Varactors
Year:
1992
Session:
2
Full-text:
Download a PDF of this paper.
Page Number(s):
115-133