THz electromagnetic waves resonantly excite plasmons in the two dimensional electron gas (2DEG) of high electron
mobility transistors (HEMTs) via grating-gate couplers. These excitations can induce measureable photoresponse.
Biasing the grating gate tunes the photoresponse via control of 2DEG carrier density. Plasmons are investigated here in
an InGaAs/InP HEMT with a 9 μm period grating gate at 78 and 106 GHz free-space radiation and 4K sample
temperature. The dependence of the photoresponse on applied Source-Drain bias is also investigated. The minimum
noise equivalent power (NEP) is estimated to be 113 pW/Hz1/2 , with maximum responsivity of 200 V/W. Such plasmonic alterations in channel conductance provide a means for voltage-tunable THz and sub-THz detectors or filters.
Split ring resonator arrays are investigated for use as active elements for the realization of voltage controllable frequency selective surfaces. Finite difference time domain simulations suggest the absorptive and reflective properties of such surfaces can be externally controlled through modifications of the split ring resonator gap impedance. In this work, such voltage-controlled resonance tuning is obtained through the addition of an appropriately designed high electron mobility transistor positioned across the split ring resonator gap. It is shown that a 0.5μm gate length high electron mobility transistor allows voltage controllable switching between the two resonant conditions associated with a split ring resonator and that of a closed loop geometry when the surface is illuminated with THz radiation. Partial switching between these two resonant conditions is observed at larger gate lengths. Such active frequency selective surfaces are proposed, for example, for use as modulators in THz detection schemes and as RF filters in radar applications when scaled to operate at GHz frequencies.
Recent progress in the investigation of millimeter-wave and THz detectors based on plasmon excitation in the twodimensional electron gas (2DEG) of a high electron mobility transistor (HEMT) is reported. A tunable resonant polarized photoresponse to mm-wave radiation in the frequency range of 40 to 110 GHz is demonstrated for a gratinggated InGaAs/InP based device. The gate consisted of a metal grating with period of 9 μm specifically designed for excitation of sub-THz plasmons. The resonant excitation of plasmons, which shifts with gate-bias, changes the channel conductance. This resonant change in channel conductance enables potential applications in chip-scale frequency-agile detectors, which can be scaled to mid-THz frequencies.
A tunable resonant photoresponse to millimeter-waves is demonstrated in a grating-gated high electron mobility
transistor (HEMT) formed by an InGaAs/InP heterostructure. The gate consists of a metal grating with 9 μm period,
which was designed to couple mm-radiation to plasmons in the two-dimensional electron gas (2DEG) of the HEMT.
The resonant excitation of plasmons, which shifts with gate-bias, changes the channel conductance. These devices have
potential as chip-scale frequency-agile mm-wave detectors, which may be scaled to THz frequencies.
The convergence of silicon photonics and infrared plasmonics allows compact, chip-scale spectral sensors. We report on
the development of a compact mid-IR spectrometer based on a broad-band IR source, dielectric waveguides, a
transformer to convert between waveguide modes and surface plasmon polaritons (SPP), an interaction region where
analyte molecules are interrogated by SPPs, an array of ring resonators to disperse the light into spectral components,
and photodetectors. The mid-IR light source emits into a dielectric waveguide, leading to a region that allows coupling
of the incident photons into SPPs. The SPPs propagate along a functionalized metal surface within an interaction region.
Interactions between the propagating SPP and any analytes bound to the surface increase loss at those wavelengths that
correspond to the analyte vibrational modes. After a suitable propagation length the SPP will be coupled back into a
dielectric waveguide, where specific wavelength components will be out-coupled to detectors by an array of ring
resonators. We have selected a 3.4 micron LED as the IR source, based on both cost and performance. Initial
experiments with circular waveguides formed from GLSO glass include measurement of the loss per mm.
Electrodynamic simulations have been performed to inform the eventual Si taper design of the proposed
photonic/plasmonic transformer. The SPP propagation length necessary for a discernible change in the signal due to
absorption in the interaction region has been estimated to be on the order of 1 mm, well within the bounds of calculated
propagation lengths for SPPs on Au.
Cathodoluminescence (CL) spectroscopy is performed on conducting 1- and 2-dimensional gratings of metals, semimetals
and semi-conductors of varying periods from 0.5 to 20 microns for a range of grating amplitudes from 0.1 to 4.6
microns. The overall emission spectrum consists of a 400 nm wide band centered at ~600 nm which depends little on the
grating period, grating amplitude, material, e-beam energy, or temperature. CL intensity increases and the center
wavelength blue shifts with increasing excitation beam current. For the larger amplitude 1-dimensional gratings fringes
appear in the emission spectrum, which is due to interference between emission from grating bars and grooves. Surface
corrugation is necessary to the emission as none is observed from smooth surfaces. The same band appears weakly in CL
of a Cu sample with random ~1 micron surface roughness, but this emission is strongly reduced when the same sample is
highly polished. The CL signal appears even when the ~10 nm electron-beam is at least 2 mm away from the grating
edge, suggesting electron-beam induced currents are important to the emission, whose precise mechanism remains
unclear. Previously suggested mechanisms--electron collision with image charge, transition radiation, surface
contamination, and inverse photoemission effect--all fail to explain the observed spectrum and its lack of beam-energy
dependence.
Conducting polymers are potentially useful materials in sensor applications. Polyaniline is one of the
most promising of these materials due to high conductivity and plasma frequencies as high as the mid-infrared.
The application of this material is still limited because of low conductivity. In this paper, we
chemically prepared a composite of co-doped polyaniline with hydrochloric acid and MSA (methane
sulfonic acid) in aqueous solution with both colloidal and nano-graphite. Solutions of the composite
material were prepared in m-cresol and NMP (N-mthyle-2-pyrrolidone), which are common organic
solvents. This approach resulted in material with conductivity higher than either intrinsic polyaniline or
graphite alone. The solution of the composite was spin coated on suitable substrates. The thicknesses of
the films were measured using atomic force microscope (AFM). Fourier transform infrared spectra
(FTIR) and micro-Raman spectra were collected to confirm the composition and determine the infrared
thickness. Surface plasmon resonances for grating patterns of this composite material were calculated
using experimental determined infrared (IR) ellipsometry data. The goal is to identify a material which
has potential application for surface plasmons resonance sensing with high sensitivity and selectivity in
IR range.
Plasmon excitation in the two dimensional electron gas (2DEG) of grating-gated high electron mobility transistors
(HEMTs) gives rise to terahertz absorption lines, which may be observed via transmission spectroscopy. Such absorption
resonances may alter the channel conductance, giving a means for tunable terahertz detection. The transmission
spectrum may be calculated analytically by making simplifying assumptions regarding the electron distribution. Such
assumptions can limit the usefulness of such analytical theories for device optimization. Indeed, significant differences
between experimentally observed resonances and theory have been noted and explained qualitatively as due to
additional, unanticipated, sheets of charge in the device. Here, we explore finite element method (FEM) simulations,
used to obtain realistic carrier profiles. Simulated plasmon spectra do not support previous explanations of red-shifting
due to interactions with additional neighboring charge distributions. Simulations do show unexpected plasmon
resonances associated with the unanticipated sheet charge, named virtual-gate, as well as the expected resonances
associated with the 2DEG. Plasmonic modes determined from these investigations are able to account for the measured
absorption lines which were previously thought to be red-shifted 2DEG plasmons. Additionally, the same simulation
approach was applied to proposed graphene-based devices to investigate their plasmon resonance spectra.
Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated InP- and
Graphene-based HEMTs are investigated. Fourier-spectrometer-obtained transmission resonances are observed over a
wide spectral band from mm wavelengths to THz frequencies. These results are found to be consistent with grating
period and 2DEG sheet charge density dependent theoretical calculations. The temperature dependence of these
transmission resonances as a function of temperature is also reported for both devices. Such devices have potential as a
chip-scale frequency-agile THz imaging spectrometers for man-portable or space-based spectral-sensing applications.
Arrays of "nanorectennas" consist of diode-coupled nanoantennas with plasmonic resonances in the visible/near-infrared
(vis/nir) regime, and are expected to convert vis/nir radiative power into useful direct current. We study plasmonic
resonances in large format (~ 1 mm2 area) arrays, consisting of electron beam-patterned horizontal (e.g., parallel to the substrate) Ag lines patterned on ultrathin (< 20 nm) tunneling barriers (NiO, NbOx, and other oxides). Our e-beam fabrication technique is scalable to large dimensions, and allows us to easily probe different antenna dimensions. These
tunneling barriers, located on a metallic ground plane, rectify the alternating current generated in the nanoantenna at
resonance. We measure the plasmonic resonances in these nanoantennas, and find good agreement with modeling,
which also predicts that the electric field driving the electrons into the ground plane (and therefore the rectification
efficiency) is considerably enhanced at resonance. Various metal-insulator-metal tunneling diodes, incorporating the
afore-mentioned barrier layers and different metals for the ground plane, are experimentally characterized and compared
to our conduction model. We observe ~ 1 mV signals from NiO-based nanorectenna arrays illuminated by 532 nm and
1064 nm laser pulses, and discuss the origin of these signals.
Mid-IR spectrometers with adequate resolution for chemical sensing and identification are typically large, heavy, and
require sophisticated non-stationary optical components. Such spectrometers are limited to laboratory settings. We
propose an alternative based on semiconductor micro-fabrication techniques. The device consists of several enabling
parts: a compact broad-band IR source, photonic waveguides, a photon-to-surface-plasmon transformer, a surfaceplasmon
sample-interaction region, and an array of silicon ring-resonators and detectors to analyze the spectrum. Design
considerations and lessons learned from initial experiments are presented.
R. Peale, Nima Nader Esfahani, Christopher Fredricksen, Gautam Medhi, Justin Cleary, Joshua Hendrickson, Walter Buchwald, Himanshu Saxena, Oliver Edwards, Michael Lodge, Ben Dawson, M. Ishigami
Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated HEMTs is
known for a variety of semiconductor systems, giving promise of chip-scale frequency-agile THz imaging
spectrometers. We present our calculations of transmission spectra and resonant photoresponse due to plasmons in InPand
graphene-based HEMTs at millimeter and THz wavelengths. Our experimental approach to measurement of
electrical response is also described. Potential applications include man-portable or space-based spectral-sensing.
A Surface Plasmon Resonance (SPR) biosensor that operates deep into the infrared (3-11 μm wavelengths) is potentially
capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to
operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra
and where the refractive index is increased by dispersion. This will provide enhanced selectivity and sensitivity, when
biological analytes bind reversibly to biomolecular recognition elements attached to the sensor surface. This paper
investigates potentially useful IR surface plasmon resonances hosts on lamellar gratings formed from various materials
with plasma frequencies in the IR wavelength range. These materials include doped semiconductors, CuSnS, graphite
and semimetal Bi and Sb. Theoretical results were compared with the experimental results. Penetration depth
measurement from the experimental complex permeabilities values shows the tighter mode confinement than for usual
Au giving better overlap with biological analytes.
Conductors with infrared plasma frequencies are potentially useful hosts of surface electromagnetic waves with sub-wavelength
mode confinement for sensing applications. Such materials include semimetals, semiconductors, and
conducting polymers. In this paper we present experimental and theoretical investigations of surface waves on doped
silicon and the conducting polymer polyaniline (PANI). Resonant absorption features were measured in reflection from
lamellar gratings made from doped silicon for various p-polarized CO2 laser wavelengths. The angular reflectance
spectra for doped silicon was calculated and compared with the experiments using experimental complex permittivities
determined from infrared (IR) ellipsometry data. Polyaniline films were prepared, optical constants determined, and
resonance spectra calculated also. A specific goal is to identify a conductor having tight mode confinement, sharp
reflectivity resonances, and capability to be functionalized for biosensor applications.
The observation of THz regime transmission resonances in an InGaAs/InP high electron mobility transistor (HEMT) can
be attributed to excitation of plasmons in its two-dimensional electron gas (2DEG). Properties of grating-based, gate-voltage
tunable resonances are shown to be adequately modeled using commercial finite element method (FEM)
software when the HEMT layer structure, gate geometry and sheet charge concentration are taken into account. The
FEM results are shown to produce results consistent with standard analytical theories in the 10-100 cm-1 wavenumber
range. An original analytic formula presented here describes how the plasmonic resonance may change in the presence
of a virtual gate, or region of relatively high free charge carriers that lies in the HEMT between the physical grating gate
and the 2DEG. The virtual gate and corresponding analytic formulation are able to account for the red-shifting
experimentally observed in plasmonic resonances. The calculation methods demonstrated here have the potential to
greatly aid in the design of future detection devices that require specifically tuned plasmonic modes in the 2DEG of a
HEMT, as well as giving new insights to aid in the development of more complete analytic theories.
Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated HEMTs is
known for a variety of semiconductor systems, giving promise of chip-scale frequency- agile THz imaging
spectrometers. In this work, we present our approach to measurement of electrical response to millimeter waves from
backward-wave oscillators (BWO) in the range 40-110 GHz for InP-based HEMTs. Frequency-modulation of the BWO
with lock-in amplification of the source-drain current gives an output proportional to the change in absorption with
frequency without contribution from non-resonant response. This is a first step in optimizing such devices for man-portable
or space-based spectral-sensing applications.
Cathodo-luminescence spectroscopy is performed on silver and gold lamellar gratings of period 7.5 or 20
microns for a range of grating amplitudes from 0.1 to 4.6 microns. The overall emission spectrum consists of a 400 nm
wide band centered at ~600 nm which depends little on the grating amplitude, metal, or e-beam energy. For the larger
grating amplitudes the emission spectrum is periodically modulated as a function of wavelength. Both the strength of the
emission envelop and the depth and phase of the modulation depend on grating orientation with respect to the light
collection axis, the distance of the excitation spot from the grating, and the distance between the grating and the
collection optics. The modulation can be explained as interference of surface emission from grating bars and grooves.
The origin of the emission remains unclear, as mechanisms of electron collision with image charge, transition radiation,
surface contamination, and inverse photo-electron effect all fail to explain the observed spectrum. This work is relevant
to the interpretation of cathodoluminescence studies of surface plasmons on structured metals for nano-photonic
applications.
THz technology has a rich history of use in the field of interstellar molecule identification where a variety of molecule
specific vibrational and rotational spectroscopic signatures exist and has been aggressively investigated for use in
advanced radar applications because of the immediate improvement in object resolution obtained at higher frequencies.
Traditionally, high power THz systems have relied upon millimeter wave sources and frequency multiplication
techniques to achieve acceptable output power levels, while lower power, table top spectroscopic systems, have relied on
broadband incoherent light sources. With the advent of high power lasers, advances in non-linear optics, and new
material systems, a number of promising techniques for the generation, detection and manipulation of THz radiation are
currently under development and are considered the enabling technologies behind a variety of advanced THz
applications.
This work presents a programmatic overview of current trends in THz technology of interest to a variety of government
organizations. It focuses on those techniques currently under investigation for the generation and detection of THz fields
motivated, for example, by such diverse applications as metamaterial spectroscopy, TH imaging, long standoff chem/bio
detection and THz communications. Examples of these new techniques will be presented which in turn will motivate the
need for the characterization of application specific active and passive THz components.
KEYWORDS: Silicon, Semiconducting wafers, Mirrors, Reflectivity, Digital signal processing, Etching, Fabry–Perot interferometers, Thin films, Gold, Chemical elements
Multi-layer thin-film optics based on alternating sub-wavelength layers of silicon and air provide high index contrast to
create improved components with just a few layers. Applications include ultra-high reflectivity mirrors, band-pass and
band-blocking filters, anti-reflection coatings, and compact high-resolution Fabry-Perot spectrometers with broad freespectral-
range. Such components may be integrated directly into airborne/satellite and man-portable sensing
instrumentation. We demonstrate a process to produce ultrathin silicon optical elements with an integral raised spacer
rim to provide the requisite air gap when these elements are combined directly into a Bragg stack. Laboratory
measurements confirm theoretical design specifications. Individual elements may be stacked and bonded to form Bragg
mirrors and other thin-film optics.
In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on
the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to
generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiNx,
sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current
streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for
coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the
lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an
external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs
when the plasmonic waves in both layers are resonantly coupled.
Arrays of "nanorectennas", consisting of nanodiode-coupled nanoantennas, are of interest for converting
visible/near-infrared (vis/nir) light into useful direct current. For efficient energy conversion, the
nanoantenna array must have a high absorbance (for different polarizations and angles of incidence) and a
large fill factor; i.e., the nanoantennas must be tightly packed together. We fabricate hexagonal, close-packed
(~ 100 nm nearest neighbor separation), large area (~ 1 cm2) arrays of vertical (e.g., perpendicular
to the substrate) Au nanowires (length < 1 μm) on Si, by electrochemically depositing gold into a porous
aluminum oxide template (a potentially inexpensive process scalable to large dimensions). Coupling of
these nanowires causes a considerable blue-shift of the plasmonic resonance of a single Au nanowire when
illuminated by p-polarized light from the infrared to the blue-green portion of the visible spectrum (similar
to the s polarization resonance), enabling a nanorectenna with tuned response in the vis/nir regime, whose
absorption is roughly polarization-independent and relatively insensitive to angle of incidence. We measure
the off-normal reflectivity of these arrays, compare with simulations, and present experimental data on
rectification and power generation in the attached Au-Si Schottky nanodiodes.
In this paper, we propose a design for a widely tunable solid-state optically and electrically pumped THz source based
on the Smith-Purcell free-electron laser. Our design consists of a thin dielectric layer sandwiched between an upper
corrugated structure and a lower layer of thin metal, semiconductor, or high electron mobility material. The lower layer
is for current streaming, which replaces the electron beam in the Smith-Purcell free-electron laser design. The upper
layer consists of two micro-gratings for optical pumping, and a nano-grating to couple with electrical pumping in the
lower layer. The optically generated surface plasmon waves from the upper layer and the electrically induced surface
plasmon waves from the lower layer are then coupled. Emission enhancement occurs when the plasmonic waves in both
layers are resonantly coupled.
A Surface Plasmon Resonance (SPR) biosensor that operates deep into the infrared (3-11 μm wavelengths) is potentially
capable of biomolecule recognition based both on selective binding and on characteristic vibrational modes. A goal is to
operate specifically at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra
and where the refractive index is increased by dispersion. This will provide enhanced sensitivity and selectivity, when
biological analytes bind reversibly to biomolecular recognition elements attached to the sensor surface. This paper
describes work on the optical and materials aspects of IR surface plasmon resonances. First, three possible coupling
schemes are considered: hemicylindrical prisms, triangular prisms, and gratings. Second, materials with plasma
frequencies one order of magnitude smaller than for noble metals are considered, including doped semiconductors and
semimetals.
Gate-voltage tunable plasmon resonances in the two dimensional electron gas of high electron mobility transistors
(HEMT) fabricated from the InGaAs/InP and AlGaN/GaN materials systems are reported. Gates were in the form of a
grating to couple normally incident THz radiation into 2D plasmons. Narrow-band resonant absorption of THz radiation
was observed in transmission for both systems in the frequency range 10 - 100 cm-1. The fundamental and harmonic
resonances shift toward lower frequencies with negative gate bias. Calculated spectra based on the theory developed for
MOSFETs by Schaich, Zheng, and McDonald (1990) agree well with the GaN results, but significant differences for the
InGaAs/InP device suggest that modification of the theory may be required for HEMTs in some circumstances.
Voltage-tunable plasmon resonances in a InGaAs/InP high electron mobility transistor (HEMT) are reported. The gate
contact consisted of a 0.5 micron period metal grating formed by electron-beam lithography. Narrow-band resonant
absorption of THz radiation was observed in transmission in the range 10 - 50 cm-1. The resonance frequency red-shifts
with increasing negative gate bias as expected. Photo-response to a tunable far-IR laser is reported. The device may
have application in high-frame-rate THz array detectors for spectral imaging with real-time chemical analysis.
KEYWORDS: Plasmons, Sensors, Terahertz radiation, Field effect transistors, Electron beam lithography, Absorption, Silicon, Signal detection, Bolometers, Electron transport
Plasmon resonances in the two dimensional electron gas (2-deg) of a high electron mobility transistor (HEMT) can affect
transport properties. The resonance frequency depends on the gate-tuned sheet charge density of the 2deg and on the
characteristic length of the gate metallization by which free space THz radiation couples to the plasmon. Thus, this type
of device can be used as a tunable detector. This work presents an experimental investigation of such a device fabricated
from the InGaAs/InP material system. E-beam lithography was used to fabricate a gate in the form of a grating with sub-micron
period. Sensitivity of the conductance to incident THz fields is reported. Direct absorption of THz, temperature
effects, and the effects of source to drain current on system performance are also investigated. It is expected that this
class of device will find use in space-borne remote sensing applications.
The intent of this investigation is to replace the low fill
factor visible sensor of a Cellular Neural Network (CNN) processor
with an InGaAs Focal Plane Array (FPA) using both bump bonding
and epitaxial layer transfer techniques for use in the Ballistic Missile
Defense System (BMDS) interceptor seekers. The goal is to fabricate
a massively parallel digital processor with a local as well as a global
interconnect architecture. Currently, this unique CNN processor is
capable of processing a target scene in excess of 10,000 frames per
second with its visible sensor. What makes the CNN processor so
unique is that each processing element includes memory, local data
storage, local and global communication devices and a visible sensor
supported by a programmable analog or digital computer program.
Plasmons can be generated with photons in the two dimensional electron gas (2-deg) of high electron mobility transistors
(HEMTs). Because the plasmon frequency at a given wavevector depends on sheet charge density, a gate bias can tune
the plasmon resonance. This effect allows a properly designed HEMT to be used as a voltage-tunable narrow-band
detector or filter. This work reports on both the theory and design of such a device in the InP materials system and
discusses its potential uses. By using a sub-micron grating to couple incident radiation to a high sheet charge 2-deg, a
minimum detectible wavelength of roughly 26 microns is obtained. Fabrication issues, terahertz response, and tunability
are discussed. Because of its small size, this novel device could find use in spaceborne remote sensing application.
A concept for a terahertz laser in vapor-phase-grown homoepitaxial GaAs with spatially periodic doping profile was theoretically explored. Monte Carlo simulation of hole transport in multilayer delta-doped p-GaAs/GaAs structures in crossed electric and magnetic fields was performed to investigate possibilities of the terahertz amplification on intervalence-band light-to-heavy hole transitions. The results are compared to those calculated for uniformly doped bulk p-GaAs and recently proposed p-Ge/Ge structures. The improvement in the gain for delta-doped p-GaAs structures is about ~2-3 times over bulk p-GaAs. Terahertz laser generation in the considered GaAs device concept appears feasible, as is growth of structures with active thicknesses sufficient to support quasioptical cavity solutions at 100 μm vacuum wavelengths. Potential applications for the considered laser device include sensing of chem/bio agents and explosives, biomedical imaging, non-destructive testing, and communications.
The Air Force Phillips Laboratory, in collaboration with the Army Research Laboratory, is developing lateral geometry, high-power photoconductive semiconductor switches (PCSS) for use in phased-array, ultra-wideband sources. The current switch utilizes an opposed contact geometry with a 0.25 cm gap spacing and is an extension of previous work on 1.0 cm PCSS devices. This work presents the development and demonstration of the 0.25 cm PCSS under both ideal laboratory conditions and potential source conditions. The laboratory configuration consists of two high-bandwidth transmission lines connected with a PCSS. The potential source configuration consists of a vector-inversion pulse generator (Blumlein) commuted with a PCSS. The 0.25 cm PCSS is shown to operate at 20 kV charge voltage, 65 ps rms switching jitter, less than 450 ps risetime and greater than 1 kHz pulse repetition rate when triggered using a compact, high-power laser diode.
We will discuss here our efforts to fabricate and test new SiC opto-electronic high voltage switches. We report the ultrafast switching of novel silicon carbide devices using an optical trigger. The switching properties of both commercial SiC pn diodes and in-house fabricated SiC thyristors were investigated. Subnanosecond risetime was observed with both devices. A comparison of SiC pn diode and thyristor switching shows that the thyristor has the highest switching speed and efficiency, and triggers with the least optical energy. We report the first optical triggering of a silicon carbide thyristor into the latched-on state. This switching is characteristic of electrically triggered thyristors, however the optical triggering produced a significantly faster risetime, 370 picosecond, than is possible with electronic triggering. The thyristor switched 100 volts bias with 96% efficiency, corresponding to a device on-state of 4 volts at an average current density of 750 A/cm2. The singular advantages of optical triggering, isolation from the trigger source, synchronized triggering of stacked devices, and switching speed, are highly desirable for high voltage, high power operation of conventional power devices. These results provide enabling technology for high-repetition rate, high-voltage impulse generators and expedite the development of high-power electrically triggered silicon carbide devices.
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