The characterization of aluminum gallium arsenide resonant tunneling diodes at microwave frequencies
Gering, Joseph Michael
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Permalink
https://hdl.handle.net/2142/22268
Description
Title
The characterization of aluminum gallium arsenide resonant tunneling diodes at microwave frequencies
Author(s)
Gering, Joseph Michael
Issue Date
1991
Doctoral Committee Chair(s)
Coleman, Paul D.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
Double-barrier, single-quantum-well, resonant tunneling diodes employing variable thickness Al$\sb{0.25}$Ga$\sb{0.75}$As barriers and 5 nm GaAs wells have been studied. Low doped GaAs buffer regions ($N\sb D$ $\approx$ 5 $\times$ 10$\sp{16}$ cm$\sp{-3}$) were placed next to the barriers to reduce the device capacitance and to prevent dopant migration into the barriers.
The diodes were mounted in a coplanar waveguide test circuit that was placed in a microwave test fixture employing Wiltron K Connector spark plug launchers to transition from the coplanar waveguide to coax. Small-signal reflection coefficient measurements were made on these diodes. The measurements were de-embedded using a two-tiered error correction scheme composed of the line-reflect-match and thru-reflect-line techniques.
A small-signal equivalent circuit model consisting of a resistor, $R\sb S$, in series with the parallel combination of a nonlinear conductance, G, and a capacitance, C, was used. The series resistance and shunt capacitance were found to be independent of bias voltage while the conductance was found to be related to the dc current-voltage characteristic $\lbrack I(V)\rbrack$ of the diode by$$G = {{dI\over dV}\over{1-{dI\over dV}R\sb S}}.$$
The large-signal behavior of the diode was investigated. The small-signal equivalent circuit model for the diode was used for the large-signal analysis by replacing the nonlinear conductance with an ac conductance, $G\sb{\rm ac}$ = $I\sb1$/$V\sb1$, where $v(t)$ = $V\sb B$ + $V\sb1$ cos $\omega t$ is the instantaneous voltage across the conductance with $V\sb B$ being the bias voltage and where $i(t)$ = $I\sb0$ + $I\sb1$ cos $\omega t$ + $I\sb2$ cos 2$\omega t$ + $\cdots$ is the Fourier series representation of the instantaneous current through the conductance as calculated from the current-voltage curve that has been corrected for the series resistance, $R\sb S$. The effects of higher harmonic voltage terms was found to be negligible.
The diode was studied as a microwave detector. When biased at the peak in the current-voltage curve, the diode provides a novel, full-wave rectification of a superimposed ac signal. The diode's performance as a detector is comparable to Schottky point contact detectors at low frequencies, while the resonant tunneling diode's performance degrades at higher frequencies because of its intrinsic parasitics.
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