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Review of wide band-gap semiconductors technology


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Silicon carbide (SiC) and gallium nitride (GaN) are typical representative of the wide band-gap semiconductor material, which is also known as third-generation semiconductor materials. Compared with the conventional semiconductor silicon (Si) or gallium arsenide (GaAs), wide band-gap semiconductor has the wide band gap, high saturated drift velocity, high critical breakdown field and other advantages; it is a highly desirable semiconductor material applied under the case of high-power, high-temperature, high-frequency, anti-radiation environment. These advantages of wide band-gap devices make them a hot spot of semiconductor technology research in various countries. This article describes the research agenda of United States and European in this area, focusing on the recent developments of the wide band-gap technology in the US and Europe, summed up the facing challenge of the wide band-gap technology.
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Review of wide band-gap semiconductors technology
Haiwei Jin
, Li Qin
, Lan Zhang
, Xinlin Zeng
, Rui Yang
Library, China Defence Science and Technology Information Center, china
Abstract.Silicon carbide (SiC) and gallium nitride (GaN) are typical representative of the wide band-gap
semiconductor material, which is also known as third-generation semiconductor materials. Compared with the
conventional semiconductor silicon (Si) or gallium arsenide (GaAs), wide band-gap semiconductor has the wide band
gap, high saturated drift velocity, high critical breakdown field and other advantages; it is a highly desirable
semiconductor material applied under the case of high-power, high-temperature, high-frequency, anti-radiation
environment. These advantages of wide band-gap devices make them a hot spot of semiconductor technology
research in various countries. This article describes the research agenda of United States and European in this area,
focusing on the recent developments of the wide band-gap technology in the US and Europe, summed up the facing
challenge of the wide band-gap technology.
Widely used of semiconductor technology in various
military fields broke the traditional concept formed in
nds of years that weapons equipment’s advantage is only
the size, the number and the more of massive destruction,
so that system of weapons become smaller, lighter, less
power wasted, higher reliable, stronger operational
effective and powerful. Military electronic equipment
required to operate at high temperature, high radiation and
other harsh environments, can detect small targets of
long-distance and real-time process high-speed sensor
data, and the operating frequency band beyond the
ordinary commercial range. Thus, require for the military
electronic equipment for semiconductor components is
much higher than ordinary electronic equipment, its safety
and reliability of components must be higher. It is worth
noting that, using conventional semiconductor technology
to produce electronic systems has been unable to meet the
requirements of next generation military applications for
volume, weight and higher reliability. Wide band-gap
semiconductor device has advantage of high frequency,
high power, high temperature and potential of resistance
to harsh environments, so that provides a method to solve
these problem.
Semiconductor of band gap greater than 2.2eV is defined
as the wide band-gap semiconductor (WBGS), typical of
wide band-gap semiconductor materials are silicon
carbide (SiC) and gallium nitride (GaN), these
semiconductor materials are also known as third-
generation semiconductor material. In comparison with Si
and GaAs as the representative of the second generation
of semiconductor, wide band gap semiconductor has
merits of wide band gap, high saturated drift velocity,
high critical breakdown electric field. in order to highlight
the advantages compared to Si and GaAs as the
representative of the second generation of semiconductors.
In recent years, as SiC single crystal growth technology
and GaN Hetero-epitaxial technology continue to mature,
wide band-gap semiconductor power device’s
development and application rise rapidly.
Figure 1. Wide band gap materials and their forbidden band
In the start-up and push of wide band-gap semiconductor
technology program (WBGSTI) of US Defense Advanced
Research Projects Agency, many other research projects
of Europe ESCAPEE and Japan NEDO, SiC, GaN and
other wide band-gap semiconductor materials and devices
research gained rapid development; a number of interna-
tional semiconductor manufacturers have introduced high-
power, high-frequency, high-temperature wide band-gap
semiconductor products, whose applications are con-
DOI: 10.1051/
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stantly expanded. In short, American and European coun-
tries will always put wide band-gap semiconductor tech-
nology on an extremely important strategic position, hesi-
tate to invest heavily to implement a number of wide band
gap semiconductor technology development plan in order
to enhance the ability of military equipment, and have
achieved good results. This article described the devel-
opment of major initiatives in Europe and America in a
wide band-gap semiconductor technology and the latest
progress in the development and research in the device. It
focused on the wide band-gap semiconductor technology
development plan implemented in US, Europe and other
developed countries and the far-reaching impact on mili-
tary or other important facilities produce, summed up the
facing challenge of the wide band-gap technology.
United States was the first country to start the wide band-
gap semiconductor technology research, and many well-
known universities and research institutions, such as Ray-
theon, TriQuint, BAE, MIT, Cree, put a lot of manpower
and material resources in the technology, and their re-
search is most outstanding. DARPA hesitated to invest
huge amounts of money to implement a number of wide
band-gap semiconductor device and circuit technology
development plans. DARPA aimed to enhance military
radar, submarines and various other systems and equip-
ment performance and reliability operated in harsh envi-
ronment, and solved a number of technical bottlenecks of
wide band-gap technology currently facing.
It is worth noting that, so far the largest investment, the
largest participating institutions, the results of the most
prominent and most influential program is counted the
wide band-gap semiconductor technology initiative
(WBGSTI), which launched by DARPA in 2002, lasted
eight years, divided in three stages; the first phase from
2002 to 2004, focused on material development, achieve
commercialization of 2-4 inches SiC substrate material,
has been completed now; the second phase from 2005 to
2007, focused on device development, used wide band
gap semiconductor material to product and demonstrate
the RF power amplifier for improving its power-added
rate, bandwidth and power density, ultimately achieved
high-volume production of high reliability, high-
performance microwave and millimeter-wave GaN-based
devices; the third stage, from 2008 to 2009, developed
GaN-based high reliable, high performance MMIC
(monolithic microwave integrated circuit), and test their
applications in a number of modules; this program cost
hundreds millions of dollars.
Figure 2. Six inchs silicon carbide crystal and single crystal
With the support of DARPA, Raytheon achieved the
world advanced level in the wide band-gap technical field,
such as the first GaN MMIC produced by Raytheon;
completed a historic first X- band GaN T / R (transmitter /
receiver modules) verification, it included with a range of
operating conditions, widely and successfully designed a
confirmatory test to verify the GaN technology maturity,
on this basis, completed a historic first X- band GaN
TRIMM (final transmitter / receiver multichannel integra-
tion module) verification, confirming the GaN perform-
ance under the relevant operating conditions, including
extensive tests in a relevant combination work environ-
ment, which including a operation test for a trial GaN
array at 1000 hours in a laboratory, and conducted GaN
array insert verification tests in a production radar, ready
for TRIMM into the production stage, as a milestone in
the success of the second phase of the WBGS project task;
in 2013 due to successful completion of the Defense Pro-
duction Act Title ċ GaN production improvement pro-
jects, it rewarded by office of the Secretary of Defense;
through this project Raytheon’s GaN production has in-
creased at least 300 percent, the cost of monolithic mi-
crowave integrated circuits decreased at least 75%. Cur-
rently GaN has become the Raytheon Company’s core
competitiveness, as well as technology pillars behind the
major project, such as air, missile defense radar and the
Next Generation Jammer. In 2014 Raytheon successfully
demonstrated the active electronically scanned array
(AESA) and gallium nitride (GaN) technology prototype
at the US "Patriot" anti-missile air defense radar system.
This technology enables 360 degree sensing coverage in
the future; it will expand the scope of defense, and to re-
duce the time of detection, identification and threat elimi-
nation. AESA technology based GaN will further improve
reliability of the "Patriot" radar and decreased life-cycle
Figure 3. GaN MMIC developed by Raytheon Company for
completing the second phase of WBGS
TriQuint Semiconductor, Inc. is a leader of GaN HEMT
developed field, with the highest level of technology in
the development of GaN alternative substrates, S-band
and X-band GaN MMIC application has achieved excel-
lent system performance. According to reports, the wide
band-gap semiconductor SiC JFET has been able to re-
place conventional Si IGBT module in the US Navy's
next-generation electric ships, such as DDG1000 systems.
System simulation results show that, with the wide band-
gap semiconductor SiC, replacing Si, many system pa-
rameters have been greatly improved. System power con-
sumption can be reduced to 1/25 of the original system;
switching speeds improved 100 to 200 times than the past.
In 2010, TriQuint Semiconductor, Inc. began to partici-
ICMES 2015
pate in third phase project of the WBGS; in May 2014 it
developed the device whose mean work time is more than
106 hours between failures at 200 ° environment, made
the successful completion of the third phase of the task.
Base the research, many wide band-gap semiconductor
devices were developed for radar.
Figure 4. Wide band gap device for radar
SiC power modules developed by Cree. will be exten-
sively used on the new aircraft of US Air Force F-
35LightingII. In power system applications, the efficiency
of the power device is higher, the advantages of system
will be more prominent, and reduce of carbon emissions
is one of the obvious advantages. According to the differ-
ence of application areas, it will also bring many other
benefits. If the wide band-gap power electronic devices
are used in hybrid electric locomotive, DC battery power
can be more efficiently converted to AC source; that can
more effectively drive the engine and reduce energy con-
sumption. Moreover, the heat dissipation of electronic
components will be reduced, so that the cooling system
will be smaller, lighter, less complex, and ultimately re-
duce the production cost, save package space, and achieve
energy saving purpose. Improving the device efficiency
may also bring a series of advantages for military aircraft
and alternative energy systems, such as improving effi-
ciency can reduce weight, reduce the requirements for the
cooling system, which can extend and expand the flying
distance and range of the aircraft.
Figure 5. F-35 ‘s radar and SIC power components
As a leader in wide band gap technology, the United
States has developed wide band-gap devices; in 2014, the
M/A-COM Company has developed a new SiC-based
GaN HEMT device, named MAGX-001214-650L00, this
transistor operates in the L-band, 650W peak power, can
reliably operate at 50V or even more extreme load adapt
conditions. This device is shown in Fig.2.
Figure 6. M / A-COM's power devices
In 2014, United States CREE Company also developed
the CGHV1F006S and CGHV1F025S two power devices,
two devices are the largest power continuous wave GaN
HEMT in the field, use dual flat no-lead package.
CGHV1F006S operating frequency covers DC-18GHz,
output power is 6W; CGHV1F025S operating frequency
covers DC-18GHz, output power is 25W.
Figure 7. CREE Company developed two power devices
The EU’s military application intention of development
wide band-gap technology is clear, in order to improve air
defense surveillance radar and performance of the high
RF wireless communication system, the EU focuses on
efficient 1 ~ 40GHz frequency range, high power, high
linearity and low cost single chip amplifier. The EU has
developed the KORRIGAN plan, which is a five-year
development plan in order to develop GaN HEMT tech-
nology in 2005. The EU hopes through carrying out the
plan to make the European Union to form a complete in-
dustrial chain of wide band-gap semiconductor technolo-
gy, which can contribute positively to the development
and application of wide band gap semiconductor technol-
Seven countries of France, Italy, Netherlands, Germany,
Spain, Sweden and the United Kingdom participate in
KORRIGAN plan. Units participated the plan covers the
technical field of materials research, circuit design, mod-
eling studies, process control, reliability evaluation, heat
treatment and packaging. In order to successfully achieve
program objectives and develop advanced GaN technol-
ogy in 2009 in accordance with established goals,
KORRIGAN plan designed demonstration system specifi-
cally to verify the validity of GaN technology in a variety
of applications, including S-band high-power amplifiers,
X-band broadband high-power amplifiers, low noise am-
plifiers and switches. In support of the EU government,
the plan goes smoothly. Thus, in recent years the EU has
made fruitful results in GaN HEMT devices and micro-
strip MMIC amplifiers research, performance of devices
and circuits continues to improve, many technology level
is highest in the world.
Figure 8. Germany developed GaN HEMT devices
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In 2010, under the leadership of the European Defence
Agency, Germany, France, Italy, Sweden and the United
Kingdom jointly launched "manufacture SiC substrate
based GaN devices and GaN epitaxial layer wafer supply
chain" (MANGA) project, the project aimed to optimize
GaN-based power electronics R & D and manufacturing,
the project major research the GaN-based transistor layer
epitaxial grown on newly developed SiC substrate, by
using the existing OEM technology, these transistor layer
are used in the manufacture of entirely European produc-
tion HEMT. In the case of not depend on international
suppliers, the EU five countries jointly developed a high-
quality GaN-based electronic devices, in 2014, the Euro-
pean Defence Agency declared that it has successfully
established the supply chain for Europe GaN-based power
Saab Company has begun to develop GaN technology
since 2005. The company will use GaN devices in its new
Gripen active electronically scanned array (AESA) radar
system. In May 2014, Saab Company announced the ap-
plication scope of its Gripen active electronically scanned
array radar system, including X-band and S-band three
types land-based systems and two types sea-based sys-
tems. According the announce of Saab company , Gripen
active electronically scanned array radar system 4A me-
dium-range version and 8A remote version are first batch
of GaN complete two-dimensional system applied to a
three-dimensional AESA multi-function radar, capable of
simultaneous air defense, air surveillance and Weapon
Figure 9. The SIC device of Infineon Company
Figure 10. Gripen’s active electronically scanned array radar
4.1 Material immature or defective
SiC single crystal material defect exists, then reduce and
eliminate the defect density, and the increase of single-
wafer size have become focuses of research. In recent
years, great progress has been made in the respect of re-
duction and eradication of fatal flaw microtubule density,
which result the SiC power semiconductor performance
and reliability decrease; Cree company began to supply 4
inches SiC single wafer of Zero Micropipes density in
2007. GaN material is immature, material defects results
the critical breakdown field decline, Buffer substrate
leakage of electricity is one of the main reasons of GaN
power devices cannot reach the material theoretical limit.
4.2 Reliability issues
Two major technical difficulties of SiC devices have not
been completely broken through: low inversion layer
channel mobility and gate oxide reliability under high-
temperature and high electric field. Through a special gate
oxidation process, SiC / SiO2 interface defects can be
eliminated to improve the inversion layer channel mobil-
ity. For SiC BJT power devices, now an urgent need to
address is the current gain degradation. The reasons of
instability caused by the current gain are still unclear; one
reason possibly is due to the stacking fault caused the
epitaxial base region. Reliability issues exist in GaN de-
vice; trap, material defects, surface treatment and passiva-
tion layer protection, Buffer substrate leakage, degrada-
tion of Schottky gate metal under high voltage and high
current and high field, insulated gate dielectric and sur-
face charge and other issues impact the GaN device reli-
4.3 Packaging issues
There are packaging problems in high-temperature, high-
power SiC, GaN device. When SiC, GaN materials and
processes problems are basically solved, Reliability issues
of the device package will rise as the main factor impact-
ing the high temperature high-power SiC, GaN device
performance. Especially GaN, with equal level of power
density of SiC, but the thermal conductivity is lower than
SiC; thus it exacerbates the problem of thermal spreading
of GaN device, and puts forward a more serious challenge
for high power GaN device package.
As the core technology of electronic, intelligence, integra-
tion and miniaturization of a new generation weapon, the
third generation of semiconductor, that is wide band-gap
semiconductor technology gets special attention of US,
Japan, the European Union and other developed countries,
for its set of advantages of small size, light weight, good
stability, high reliability, low power consumption and so
on. A number of wide band-gap semiconductor technol-
ogy development programs implemented in these coun-
tries will make the wide band-gap semiconductor technol-
ogy research continue to rise to new levels, so that a vari-
ety of wide band-gap semiconductor devices become sat-
ellite communications, high-speed computers, precision-
guided, early warning and detection, intelligence and re-
connaissance, electronic warfare, intelligent fire control
systems and other military equipment’s necessary and
important components.
ICMES 2015
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... In power electronics systems, the usage of WBG power devices can lead to optimized design solutions in terms of passive components, converter topologies, and thermal management. WBG-based power devices play an important role in different applications [29], and because of their properties, these materials have become suitable for reducing the volume, weight, and costs. In order to accommodate the high power and frequencies, several manufacturers are using WBG materials for electric vehicles, and other applications since it outperforms the limits of silicon and guarantees excellent performance in critical operating environments. ...
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Power electronic systems have a great impact on modern society. Their applications target a more sustainable future by minimizing the negative impacts of industrialization on the environment , such as global warming effects and greenhouse gas emission. Power devices based on wide band gap (WBG) material have the potential to deliver a paradigm shift in regard to energy efficiency and working with respect to the devices based on mature silicon (Si). Gallium nitride (GaN) and silicon carbide (SiC) have been treated as one of the most promising WBG materials that allow the performance limits of matured Si switching devices to be significantly exceeded. WBG-based power devices enable fast switching with lower power losses at higher switching frequency and hence, allow the development of high power density and high efficiency power converters. This paper reviews popular SiC and GaN power devices, discusses the associated merits and challenges, and finally their applications in power electronics.
... It has been observed that upon incorporating substituents at meta positions with respect to nitrogen atom of Bpy, the optical band gap values decreases from Eu1 to Eu4. This gap is responsible for their conducting behavior and potential utilization in electronic technology [34]. ...
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Trivalent europium complexes exhibit good luminescent characteristics. A series of octacoordinated ternary europium complexes with fluorinated diketone and heteroaromatic auxiliary unit were synthesized. The synthesized europium complexes were characterized by elemental, thermal, electrochemical and spectroscopic analyses. Band gap values lie in range of semiconductors which confirm the conducting behavior of prepared complexes. Photoluminescence spectra were recorded in solid state and DMSO solvent. Emission spectral profiles have displayed most intense peak at ~ 612 nm corresponding to hypersensitive ⁵D0 → ⁷F2 transition. Colorimetric parameters suggest red luminous nature of europium complexes. The luminescent heteroleptic europium complexes might be utilized as emissive materials for fabricating display. Graphical Abstract
... Slight change in value of E g from C1 to C6 complexes can be explained on account of secondary ligand present in complexes C2 -C6. The determined band gap value of synthesized complexes provided their good intrinsic conductivity behavior and their possible application in radar, photovoltaic cell and laser systems [54,55]. Further, presence of two band gap value could be attributed the two-charge transfer process from ligand to metal ion and efficient for solar energy conversion [56]. ...
The scarlet Sm (III) complexes with eight coordination number, as favoured by EDAX and elemental analytical data, were synthesized with fluorinated β –keto carboxylic acid as primary ligand and neo, batho, phen, dmph, and bypy as secondary ligand. Binary and ternary complexes of Sm(III) ion [Sm(ligand)32H2O], [Sm(ligand)3secondary ligand] respectively were prepared by one-step grinding method. The complexes exhibit crystalline character, nanoparticle size and outstanding thermal stability, they also have high color purity and as warm orange light sources. In UV visible light, complexes display several characteristic emission transitions such as (⁴ G5/2 → ⁶ H5/2, ⁴ G5/2 → ⁶ H7/2 and ⁴ G5/2 → ⁶ H9/2) under the excitation of Sm (III) ion. The scarlet luminescence in UV domain is accredited to the ⁴ G5/2 → ⁶ H7/2 transition at 605 nm wavelength. The proton NMR and FT-IR data are reliable with coordination behavior of organic ligand and secondary ligand with Sm(III) ion. To understand the semiconducting nature, materiality in solar cell and photovoltaic devices with the help of HOMO- LUMO bandgap analysis and Urbach energy were examined. The calculated Judd-Ofelt parameter is a crucial aspect to describe the rigidity and symmetry of complexes. The anti-microbial investigation demonstrated that all complexes are practically applicable in bioassays.
... To further illustrate interpretation of global and local modeling approaches, we present another case study, using modeling of wide bandgap vs non-wide bandgap vdW semiconductor materials. Materials that exhibit large bandgaps are essential for high-temperate and high-power device applications due to their ability to maintain electronic functionalities at high ambient temperature environments [55][56][57][58]. Furthermore, multiple studies of vdW materials in the past decade have led to a recent surge of interest in wide bandgap vdW materials for next-generation electronic devices [59][60][61][62][63][64]. ...
Traditionally, materials discovery has been guided by basic physical rules, and such rules embody the basic understanding of the physical characteristics of interest of the material. However, the discovery of physical rules remains a challenging task due to the inherent difficulty in recognizing patterns in the high-dimensional and highly nonuniform distributed materials space. The standard data analytics approach using machine learning (ML) may fall short in producing meaningful results due to fundamental differences between the underlying assumptions and goals of ML vs materials discovery. ML is mainly focused on estimating complex black-box predictive models (that are nonlinear and multivariate), whereas in materials discovery, the goal is to come up with interpretable data-driven physical rules. Here, we attempt to tackle this problem by proposing a robust data analytics framework that allows us to derive basic physical rules from data. We introduce the concept of global and local modeling, utilizing both supervised and unsupervised learning, for highly nonuniformly distributed materials data. To enhance the model interpretation, we also introduce a model-independent interpretation technique to assist human experts in extracting useful physical rules. The proposed framework for extracting data-derived physical rules at the global and local level is illustrated using two case studies: (1) classification of van der Waals (vdW) and non-vdW (nvdW) materials and (2) classification of wide bandgap and non-wide bandgap vdW materials.
Four green luminescent Tb(III) complexes have been synthesized using a bidentate ligand 6,8-dichlorochromone-3-carboxaldehyde (L) and neutral heterocyclic ancillary ligands. The complexes showed characteristic Tb(III) ion emission bands at 491 nm, 546 nm, 586 nm, and 623 nm, on irradiation with 345 nm. The excellent green luminescence shown by the complexes is due to prominent 5D4→7F5 transition at 546 nm. Three primary ligands and one secondary ligand around the metal ion provide a highly shielded environment, leading to enhanced luminescence properties of synthesized ternary complexes such as quantum yield (ϕTb = 48.76 %); longer lifetime period (τobs = 0.734 ms); intrinsic quantum yield (ηTb = 23.67 %); and radiative rate (KRad = 6.64 × 102 s−1). The ternary complexes deliver higher thermal stability, up to 170 °C.
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This research article deals with the synthesis of ternary Sm³⁺ complexes with 6,8-dichlorochromone-3-carboxaldehyde through solution-precipitation method. The photometric properties of resultant complexes were tuned by coordinating N-donor heterocyclic ligands with Sm³⁺ ion. The emission spectra, obtained in the visible region have been studied. Under optical excitation of 370 nm, the complexes displayed characteristic Sm³⁺-centered emission peaks at ~ 563, 600 and 647 nm in solution as well as in powder state. The complexes showed thermal stability up to 175 °C. The complexes delivered quantum yield as high as 7.91% and longest emission lifetime of 0.564 ms. The color coordinates of the complexes, located in deep orange (in solution) and red (in powder) spectral region, matched well with the Society of Motion Picture and Television Engineers and European Broadcasting Union. The properties of complexes have been investigated to a significant extent due to their easy synthesis and potential applications as orange-red light emitter in a wide range of photonic applications such as display devices, OLEDs, dashboards, optical systems.
Ta-doped Ga2O3 (Ga2O3:Ta) epitaxial films were grown on SrTiO3 (100) substrates via an MOCVD system. Solar-blind ultraviolet (UV) detectors with a metal-semiconductor-metal structure were fabricated based on the β-Ga2O3:Ta films, and the effects of Ta doping concentration on the photo response were investigated. The surface morphology, composition and band gap of the films were characterized. The β-Ga2O3:Ta UV detectors showed photo response characteristics under 222 nm deep UV light. As the Ta doping concentration increased, the responsivity of the detector increased significantly. For the 1.5 at.% Ta doped UV detector, the responsivity under 222 nm UV light at 8 V bias reached 8.23 A W⁻¹, and the light-dark current ratio is close to 10³. Moreover, the responsive rise time (Tr1/Tr2) and decay time (Td1/Td2) at 1 V bias were as short as 0.37 s/0.38 s and 0.41 s/0.85 s, respectively. Ta doping significantly improves the performance of β-Ga2O3 ultraviolet detectors, which may be a feasible method to expand its application potential.
This paper presents four octa coordinated ternary terbium complexes based on 2-benzoylacetophenone (BAP) and other auxiliary ligands. For characterization purpose, elemental analysis, electrochemical study, thermal analysis and spectroscopic investigations were carried out in detail. Optical band gap (3-4 eV) of complexes was determined from Tauc’s relation. Upon excitation in UV region, emission spectra of complexes demonstrate peaks of Tb³⁺ ion at ∼616 nm, 589 nm, 548 nm, and 492 nm, attributed to ⁵D4→⁷FJ (J= 3 to 6) respectively due to energy transfer from ligand to Tb(III) ion via antenna effect. Peak at 548 nm corresponding to ⁵D4→⁷F5 is responsible for bright green emission of synthesized terbium complexes. CIE color coordinates and color purity further corroborate the green emission of Tb³⁺ complexes. The complexes were found to be quite stable as studied by thermal analysis. The outcomes of characterizations have demonstrated that these complexes could behave as good contenders in lighting systems and displays owing to their photometric characteristics.
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The development of semiconductor electronics is reviewed briefly, beginning with the development of germanium devices (band gap E g = 0.66 eV) after World War II. A tendency towards alternative materials with wider band gaps quickly became apparent, starting with silicon (E g = 1.12 eV). This improved the signal-to-noise ratio for classical electronic applications. Both semiconductors have a tetrahedral coordination, and by isoelectronic alternative replacement of Ge or Si with carbon or various anions and cations, other semiconductors with wider E g were obtained. These are transparent to visible light and belong to the group of wide band gap semiconductors. Nowadays, some nitrides, especially GaN and AlN, are the most important materials for optical emission in the ultraviolet and blue regions. Oxide crystals, such as ZnO and β-Ga2O3, offer similarly good electronic properties but still suffer from significant difficulties in obtaining stable and technologically adequate p-type conductivity.
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Dramatic progress has been achieved, during Phase II of the Wide Band Gap Semiconductors for RF Applications (WBGS-RF) program, sponsored by the Defense Advanced Research Projects Agency (DARPA), in extending the lifetime of high performance gallium nitride high electron mobility transistors, operating at frequencies up to 40 GHz. This paper summarizes the significant progress made by the contractor teams participating in the Phase II portion of the program.
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We demonstrate a single-chip switch-mode boost converter that features a monolithically integrated lateral field-effect rectifier (L-FER) and a normally off transistor switch. The circuit was fabricated on a standard AlGaN/GaN HEMT epitaxial wafer grown with GaN-on-Si technology. The fabricated rectifier with a drift length of 15 mum exhibits a breakdown voltage of 470 V, a turn-on voltage of 0.58 V, and a specific on-resistance of 2.04 mOmegaldrcm<sup>2</sup>. The L-FER exhibits no reverse recovery current associated with the turn-off transient because of its unipolar nature. A prototype of GaN-based boost converter that includes monolithically integrated rectifiers and transistors is demonstrated using conventional GaN-on-Si wafers for the first time to prove the feasibility of the GaN-based power IC technology.
Wide band gap semiconductors, and in particular silicon carbide (4H-SiC) and gallium nitride (GaN), are very promising materials for the next generation of power electronics, to guarantee an improved energy efficiency of devices and modules. As a matter of fact, in the last decade intensive academic and industrial research efforts have resulted in the demonstration of both 4H-SiC MOSFETs and GaN HEMTs exhibiting /Ron performances well beyond the silicon limits.In this paper, some of the present scientific challenges for SiC and GaN power devices technology are reviewed. In particular, the topics selected in this work will be the SiO2/SiC interface passivation processes to improve the channel mobility in 4H-SiC MOSFETs, the current trends for gate dielectrics in GaN technology and the viable routes to obtain normally-off HEMTs.
Ultralow on-resistance silicon carbide static induction transistors with buried gate structures (SiC-BGSITs) have been successfully developed through innovative fabrication process. A submicrometer buried p<sup>+</sup> gate structure was fabricated by the combination of submicrometer trench dry etching and epitaxial growth on a trench structure. The breakdown voltage V<sub>BR</sub> and specific on-resistance R<sub>onS</sub> of the fabricated SiC-BGSIT were 700 V at a gate voltage V<sub>G</sub>=-12V, and 1.0 mOmegamiddotcm<sup>2</sup> at a current density J<sub>D</sub>=200A/cm<sup>2</sup> and V<sub>G</sub>=2.5V, respectively. This R<sub>onS</sub> is the lowest on-resistance for ~600 V class power switching devices, including other SiC devices and GaN HEMTs
A high electron mobility transistor (HEMT)-compatible power lateral field-effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN/GaN HEMT, providing a low-cost solution for GaN power integrated circuits. The power rectifier features a Schottky-gate-controlled two-dimensional electron gas channel between the cathode and anode. By tying up the Schottky gate and anode together, the forward turn-on voltage of the rectifier is determined by the threshold voltage of the channel instead of the Schottky barrier. The L-FER with a drift length of 10 μm features a forward turn-on voltage of 0.63 V at a current density of 100 A/cm2. This device also exhibits a reverse breakdown voltage (BV) of 390 V at a current level of 1 mA/mm and a specific on resistance (RON,sp) of 1.4 mΩ cm2, yielding a figure of merit (BV2/RON,sp) of 108 MW/cm2. The excellent device performance, coupled with the lateral device structure and process compatibility with AlGaN/GaN HEMT, make the proposed L-FER a promising candidate for GaN power integrated circuits.
In this paper, recent advances in GaN-based transistors for power switching and millimeter wave communications are reviewed. These two applications are emerging in addition to the widely developed power amplifiers at microwave frequencies mainly for cellular base stations. Reduction of the fabrication cost is strongly required for power switching GaN transistors, which is enabled by our epitaxial growth technology on large area Si substrates. Another requisite for the application is to achieve normally-off operation and our novel device structure called Gate Injection Transistors (GIT) enables it with low enough specific on-resistance (Ron · A) and high drain current. Here, we also present the world highest breakdown voltage of 10400 V in AlGaN/GaN HFETs, extracting full advantage of the high breakdown strength of GaN. The used poly AlN passivation works as a surface heat spreader with its high thermal conductivity, which effectively relieves the channel temperature resulting in lower thermal resistances. The GaN device for future millimeter wave communication consists of MIS-type gate using so-called “in-situ” deposited SiN as a gate insulator, which exhibits high fmax of 203 GHz and low noise figure of 1.4 dB at 28 GHz. The presented GaN transistors are promising for the two future emerging applications demonstrating high enough potential of the material systems. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Conference Paper
Technologies to enable the next generation of transmit/receive modules for sensor and communications systems are being pursued in programs funded by the Defense Advanced Research Projects Agency (DARPA). DARPA programs contributing to dramatically improved performance and wafer-scale integration for T/R modules will be highlighted. These programs include the Wide Band Gap Semiconductors for RF Applications (WBGS-RF) program, the Scalable Millimeter Wave Architectures for Reconfigurable Transceivers (SMART) program, the Integrated Sensor Is Structure Critical Technology Demonstration (ISIS-CTD), and the Sub-millimeter Wave Imaging Focal-plane Technology (SWIFT) program.
Conference Paper
The emergence of high-voltage, high-frequency (HV-HF) silicon-carbide (SiC) power devices is expected to revolutionize commercial and military power distribution and conversion systems. The DARPA wide bandgap semiconductor technology (WEST) high power electronics (HPE) program is spearheading the development of HV-HF SiC power semiconductor technology. In this paper, some of the recent advances in development of HV-HF devices by the HPE program are presented and the circuit performance enabled by these devices is discussed
Conference Paper
GaN smart power chip technology has been realized using GaN-on-Si HEMT platform, featuring monolithically integrated high-voltage power devices and low-voltage peripheral devices for mixed-signal functional blocks. Two imperative functional blocks for smart power applications with wide-temperature-range stability are demonstrated. The first one is a voltage reference generator, and the second one is a temperature-compensated comparator. These circuits are capable of proper functions within a wide temperature range from room temperature up to 250degC, illustrating the unique advantage of the wide-bandgap GaN. The voltage reference generator was designed with an AlGaN/GaN HEMT and Schottky diodes, and the devices were operated in the subthreshold regime to obtain low power consumption. The voltage reference generator achieved an average drift of less than 70 ppm/degC and can be used as a reference voltage in various biasing and sensing circuits. The temperature-dependent performance of a conventional comparator is characterized and a new temperature-compensated comparator circuit is proposed. The positive limiting level of the temperature-compensated comparator is less than 450 ppm/degC drift compared to 1350 ppm/degC in the conventional comparator.