bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact Ionization in 4H-SiC Nuclear Radiation Detectors
Authors: Ivanov Alexander M. , Mynbaeva Marina G. , Sadokhin Anton V. , Strokan Nikita B. , Lebedev Alexander A.
Published: May 2010

Nonequilibrium-charge transport has been studied in a structure with a Schottky barrier fabricated on a CVD-grown n-4H-SiC film. The charge introduced by single α-particles was recorded by nuclear spectrometric techniques. The maximum electric field strength in the structure was 1.1 MV/cm. The recorded charge as a function of the reverse bias applied to the structure shows a superlinear rise. Simultaneously, the width of the amplitude spectrum increased superlinearly, too. The observed effect is attributed to the initial stage of impact ionization. The manifestation of the process at unusually low fields (~1.0 MV/cm) is accounted for by specific features of the charge generation process. The carriers generated by a α-particle are found to be originally "heated". The results obtained allow prognostication of the appearance of SiC detectors of the "proportional counter" type in the near future. This is enabled by the advances made in the field of high-voltage electronics in obtaining in practice the required electric field strengths.
Characterisation of Low Noise 4H-SiC Avalanche Photodiodes
Authors: Green James E. , Loh W.S. , David John P.R. , Tozer R.C. , Soloviev Stanislav I. , Sandvik Peter M.
Published: May 2010

We report photomultiplication, M, and excess noise, F, measurements at 244nm and 325nm in two 4H-SiC separate absorption and multiplication region avalanche photodiodes (SAM-APDs). Sample A is a 4 x 4 array of 16 SAM-APDs. This structure possesses a relatively thin absorption layer resulting in more mixed injection, and consequently higher noise than sample B. The absorption layer of sample B does not deplete, so 244nm light results in >99% absorption outside the depletion region resulting in very low excess noise. Both structures exhibit very low dark currents and abrupt uniform breakdown at 194V and 624V for samples A and B respectively. Excess noise is treated using a local model [1]. The effective ratio of impact ionisation coefficients (keff) is approximately 0.007, this indicates a significant reduction in the electron impact ionisation coefficient, α, compared to prior work [2-5]. We conclude that the value of α will require modification if thick silicon carbide structures are to fit the local model for multiplication and excess noise.
Fabrication and Characteristics of Micro Heaters Based on Polycrystalline 3C-SiC for High Temperature and Voltage
Authors: Chung Gwiy Sang , Jeong Jae Min
Published: May 2010

This paper describes fabrication and properties of polycrystalline 3C-SiC micro heaters built on AlN(0.1 μm)/3C-SiC(1.0 μm) suspended membranes using surface micromachining technology. 3C-SiC and AlN semiconductors which have a large energy band gap and very low lattice mismatch were used as sensors in harsh environment micro electromechanical system (MEMS) applications in this work. The 3C-SiC thin film was simultaneously used as a resistance of temperature detector (RTD) and micro heater for detecting heated temperature correctly. The thermal coefficient of resistance (TCR) of the implemented 3C-SiC RTD is about -5200 ppm/°C in the temperature range from 25°C to 50°C and -1040 ppm/°C at 500°C. The 3C-SiC micro heater generates about 500°C of heat at 10.3 mW. Moreover, 3C-SiC micro heaters stand at higher applied voltages than case of Pt micro heaters.
Silicon Carbide Based Energy Harvesting Module for Hostile Environments
Authors: Barker Simon , Miao Bing , Brennan Daniel , Vassilevski Konstantin , Wright Nicolas G. , Horsfall Alton B.
Published: May 2010

This paper demonstrates the rst high temperature silicon carbide based energy
harvesting module suitable for use in hostile environments. The system comprises a of SiC pin photovoltaic cell, HfO2 based capacitive storage bank and Schottky blocking diode. The system demonstrates the ability to harvest energy from a UV rich environment and store this
energy on a HfO2 metal - insulator - metal (MIM) capacitor bank. The system unies work thathas focussed on developing high temperature energy harvesting technologies, a key technology
in facilitating the deployment of resilient wireless sensor nodes into hostile environments. The system demonstrates the capability to store an initial voltage of 2.3V decaying to 0.5V in 300ms
with a Schottky based system. Replacing the Schottky diode with a switched system, a much lower decay rate to 1.5V in over 8s was observed. This shows that an effective harvester could be made with a switched power controller.
New Generation of SiC Based Biodevices Implemented on 4” Wafers
Authors: Godignon Philippe , Martin Iñigo , Gabriel Gemma , Gomez Rodrigo , Placidi Marcel , Villa Rosa
Published: May 2010

Silicon Carbide is mainly used for power semiconductor devices fabrication. However, SiC material also offers attractive properties for other types of applications, such as high temperature sensors and biomedical devices. Micro-electrodes arrays are one of the leading biosensor applications. Semi-insulating SiC can be used to implement these devices, offering higher performances than Silicon. In addition, it can be combined with Carbon Nanotubes growth technology to improve the devices sensing performances. Other biosensors were SiC could be used are microfluidic based devices. However, improvement of SiCOI starting material is necessary to fulfill the typical requirements of such applications.
SiC vs. Si - Evaluation of Potentials for Performance Improvement of Power Electronics Converter Systems by SiC Power Semiconductors
Authors: Biela Jürgen , Schweizer Mario , Waffler Stefan , Wrzecionko Benjamin , Kolar Johann Walter
Published: May 2010

Switching devices based on wide band gap materials as SiC oer a signicant perfor-
mance improvement on the switch level compared to Si devices. A well known example are SiC
diodes employed e.g. in PFC converters. In this paper, the impact on the system level perfor-
mance, i.e. eciency/power density, of a PFC and of a DC-DC converter resulting with the new
SiC devices is evaluated based on analytical optimisation procedures and prototype systems.
There, normally-on JFETs by SiCED and normally-off JFETs by SemiSouth are considered.
Fully-Integrated 6H-SiC JFET Amplifiers for High-Temperature Sensing
Authors: Patil Amita , Fu Xiao An , Mehregany Mehran , Garverick Steven
Published: May 2010

Fully monolithic, transimpedance and differential voltage amplifiers are reported in this paper based on 6H-SiC, n-channel, depletion-mode JFETs. The single-stage transimpedance amplifier has a low-frequency gain of ~222 kΩ at room temperature, with ~2% gain matching for copies on a 6-mm x 6-mm die. The transimpedance gain is set by an integrated resistor and is ~1.1 MΩ at 450oC. The single-stage, differential voltage amplifier has a typical gain-bandwidth of ~2.8 MHz at 600oC and a typical open-loop voltage gain of ~35.8 dB at 25oC, with less than 1-dB gain variation from 25-600oC.
Fabrication of SiC JFET-Based Monolithic Integrated Circuits
Authors: Fu Xiao An , Patil Amita , Lee Te Hao , Garverick Steven , Mehregany Mehran
Published: May 2010

We report fabrication of lateral, n-channel, depletion-mode, junction-field-effect-transistor (JFET) monolithic analog integrated circuits (ICs) in 6H-SiC. Ti/TaSi2/Pt forms the contact metalization, Ti/Pt the interconnect metal, and the SiO2/Si3N4/SiO2 interlayer dielectric. The threshold voltage and pinch off current indicate that the actual channel doping and thickness is close to the nominal values specified. The wafer yield for good circuits of a single-stage differential amplifier is 54% out of 46 copies.
Inverter Loss Reduction Using 3kV SiC-JBS Diode and High-Speed Drive Circuit
Authors: Ishikawa Katsumi , Ogawa Kazutoshi , Kameshiro Norihumi , Onose Hidekatsu , Nagasu Masahiro
Published: May 2010

We developed a JBS diode with characteristics of a low forward voltage and a low leakage current at 3kV. Further, we built a prototype of a 3kV/200A hybrid module, equipped with Si-IGBTs and SiC-JBS diodes. We attempted to decrease the recovery loss, and the decrease in the turn-on power loss, by using a hybrid module and a high-speed drive circuit. Moreover, we estimated that the total energy loss of the converter and the inverter were reduced to about 33%.
NMOS Logic Circuits Using 4H-SiC MOSFETs for High Temperature Applications
Authors: Le-Huu Martin , Schrey Frederik F. , Grieb Michael , Schmitt H. , Haeublein Volker , Bauer Anton J. , Ryssel Heiner , Frey L.
Published: May 2010

Normally-off 4H-SiC MOSFETs are used to build NMOS logic gates intended for high temperature operation. The logic gates are characterized between 25°C and 500°C. Stable gate operation for more than 200h at 400°C in air is demonstrated. The excellent MOS reliability is quantified using I-V curves to dielectric breakdown and constant voltage stress to breakdown at 400°C. Although the effective tunneling barrier height B for electrons lowers to 2eV at 400°C, the extrapolated lifetime from constant voltage stress to breakdown measurements is longer than 105h at 400°C for typical logic gate operating field strength of 2MV/cm.
Short-Length Step Morphology on 4° Off Si-Face Epitaxial Surface Grown on 4H-SiC Substrate
Authors: Momose Kenji , Odawara Michiya , Tajima Yutaka , Koizumi Hiroo , Muto Daisuke , Sato Takayuki
Published: May 2010

We developed a production technology for epitaxial growth with a smooth surface morphology for 4º off Si-face 4H-SiC epitaxial layers on 100 mm-diameter substrates. High-contrast topography images by optical surface analyzer revealed that a step bunching free surface was obtained throughout the whole area of the wafer surface. However, short-length steps still remained locally on the epitaxial surfaces. Using photoluminescence imaging, it was clarified that the short-length steps were morphological in nature and did not contain stacking faults. The short-length steps were generated by step-flow growth pinning caused by the shallow pits of threading screw dislocations revealed by molten KOH etching.
Design and Characterization of 50W Switch Mode Power Supply Using Normally-On SiC JFET
Authors: Kang In Ho , Joo Sung Jae , Bahng Wook , Kim Sang Cheol , Kim Nam Kyun
Published: May 2010

The 50W Quasi-resonant mode SMPS which adopted a normally-on-type SiC JFET as a switch has been designed and characterized. A simple decision circuit and an auxiliary power supply was utilized to safely protect the JFET from an in-rush current at initial operation stage and to provide sufficient negative voltage for a complete JFET drive. Even without a refine engineering, the SMPS showed 96% efficiency at a full load state.
Fabrication and Testing of 4H-SiC MESFETs for Analog Functions Circuits
Authors: Devie Arnaud , Tournier Dominique , Godignon Philippe , Vellvehi Miquel , Montserrat Josep , Jordá Xavier
Published: May 2010

Lateral normally-on dual gates MESFETs withstanding a drain/source voltage in excess of 200V have been fabricated on semi-insulating 4H-SiC substrate. This paper reports on the fabrication, DC characterization and in-circuit behavior of the MESFETs. Temperature dependent DC characterization has been carried out up to 473K. The performances of basic analog circuits such as an amplifier and a clock, using these MESFETs, are detailed and analyzed.
Discussion of Turn on Current Peaks of SiC Switches in Half Bridges
Authors: Koch Immo , Canders Wolf Rüdiger
Published: May 2010

The optimal control parameters for semiconductor switches at the development state with new materials and structures are often unidentified. By using those sample switches with a gate control set by investigating one switch only, parasitic influences might lead to increased switching losses in half bridges [1, 2]. The focus of this paper is on an effect at turn on by using for example normally on JFET as high and low side switch. At this an increased current peak might occur which leads to higher switching losses. By adjusting the gate voltage losses can be economized.
Evolution of the Electrical Behaviour of GaN and AlGaN Materials after High Temperature Annealing and Thermal Oxidation
Authors: Roccaforte Fabrizio , Iucolano Ferdinando , Giannazzo Filippo , Di Franco Salvatore , Bongiorno Corrado , Puglisi Valeria , Raineri Vito
Published: May 2010

In this paper, the evolution of the electrical behaviour of GaN and AlGaN materials after high-temperature annealing and thermal oxidation is discussed. In particular, annealing above 1100°C, required for electrical activation of implanted species, increases the surface state density, reducing the metal/GaN Schottky barriers and increasing the leakage current. On the other hand, the thermal oxidation at 900°C of AlGaN/GaN heterostructures showed the formation of a thin oxide layer, which can be able to passivate surface defects and/or can serve as inter-device isolation. However, a decrease of the sheet carrier density in the two dimensional electron gas (2DEG) was observed when the material is subjected to such high thermal budgets. The results are discussed considering the possible optimizations and applications to GaN-devices technology.
Effect of Temperature and Al Concentration on the Electrical Performance of GaN and Al0.2Ga0.8N Accumulation-Mode FET Devices
Authors: Tadjer Marko J. , Hobart Karl D. , Mastro Michael E. , Anderson Travis J. , Imhoff Eugene A. , Kub Fritz J. , Hite Jennifer K. , Eddy Charles R.
Published: May 2010

Field-effect transistors were fabricated on GaN and Al0.2Ga0.8N epitaxial layers grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrates. The threshold voltage VTH was higher when AlGaN was used as an active layer. VTH also increased with temperature due to the increased positive polarization charge at the GaN/AlN buffer/sapphire interfaces. Drain current increased at high temperatures even with more positive threshold voltage, which makes GaN-based FET devices attractive for high temperature operation.
2H-AlGaN/GaN HEMTs on 3C-SiC(111)/Si(111) Substrates
Authors: Tonisch Katja , Jatal Wael , Granzner Ralf , Kittler Mario , Baumann Uwe , Schwierz Frank , Pezoldt Joerg
Published: May 2010

We present the realization of high electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures grown on silicon substrates using a SiC transition layer. The growth of AlGaN/GaN heterostructures on Si (111) was performed using metalorganic chemical vapour deposition (MOCVD). The (111) SiC transition layer was realized by low pressure CVD and prevented Ga-induced meltback etching and Si-outdiffusion in the subsequent MOCVD growth. The two-dimensional electron gas (2DEG) formed at the AlGaN/GaN interface showed an electron sheet density of 1.5x1013 cm-3 and a mobility of 870 cm²/Vs proving the high structural quality of the heterostructure. Device processing was done using electron beam lithography. DC and RF characteristics were analysed and showed a peak cut-off frequency as high as 6 GHz for a 1.2 µm gate HEMT.
High Temperature Characteristics of Diamond SBDs
Authors: Umezawa Hitoshi , Ikeda Kazuhiro , Kumaresan Ramanujam , Shikata Shinichi
Published: May 2010

Because of the superior material properties of diamond, high performance in high-temperature power device application is demonstrated in both the computational and the experimental studies. A calculated Baliga limit of diamond Schottky barrier diode (SBD) based on 1D model indicates that an increase in on-resistance is highly expected within the high blocking voltage region and will be remarkable at high temperature conditions. Because of the high barrier height of diamond SBDs, the reverse leakage current is suppressed even at high temperatures. From the high-temperature stability test, stable interfaces of metal/diamond contact with constant Schottky barrier height have been confirmed. The SBD works for more than 1500 hrs at 400oC.
Nitrogen Centers in Nanodiamonds: EPR Studies
Authors: Soltamova Alexandra A. , Baranov P.G. , Ilyin Ivan V. , Vul' A.Y. , Kidalov S.V. , Shakhov F.M. , Mamin G.V. , Silkin N.I. , Orlinskii S.B. , Salakhov M.K.
Published: May 2010

Electron paramagnetic resonance (EPR) and electron spin echo (ESE) at X-band (9.4 GHz) and W-band (94 GHz) have been used to study defects in natural diamond nanocrystals, detonation nanodiamond (ND) with a size of  4.5 nm and detonation ND after high-pressure high-temperature (HTHP) sintering with a size of  8.5 nm. Based on identification of atomic nitrogen centers N0 and nitrogen pairs N2+ detected by means of the high frequency EPR and ESE in natural diamond nanocrystals, atomic nitrogen centers N0 have been discovered in nanodiamond core in detonation ND and detonation ND after sintering. In addition EPR signal of multi-vacancy centers with spin 3/2 seems to be observed in diamond core of detonation ND.
High-Speed Growth of High-Quality 4H-SiC Bulk by Solution Growth Using Si-Cr Based Melt
Authors: Danno Katsunori , Saitoh Hiroaki , Seki Akinori , Daikoku H. , Fujiwara Y. , Ishii T. , Sakamoto H. , Kawai Yoichiro
Published: May 2010

High-speed solution growth using Si-Cr based melt has been performed on on-axis 4H-SiC(0001) at a high temperature of about 2000°C. The maximum growth rate for one-hour growth reaches to 1120 m/h, while the typical growth rate of growth for 2h is about 500 m/h. A large crystal that is about 25 mm in diameter and 1650 m in thickness can be obtained by growth for 5h. The crystal quality is confirmed to be homogeneous by X-ray diffraction and X-ray topography, because FWHM is less than 30 arcsec. Etch pit density of the threading dislocations in the grown crystal is 103-104 cm-2, and that of basal plane dislocation is 2×102-3×103 cm-2. Resistivity of the crystals grown by the solution growth is comparable to those of crystals grown by physical vapor transport technique.
The Deposition of 3C-SiC Thin Films onto the (111) and (110) Faces of Si Using Pulsed Sputtering of a Hollow Cathode
Authors: Huguenin-Love James , Lauer Noel T. , Soukup Rodney J. , Ianno Ned J. , Kment Štepan , Hubička Zdenek
Published: May 2010

Thin films of SiC have been deposited using a hollow cathode sputtering technique. Several methods have been used including DC, RF, and pulsed sputtering. The films reported here have been deposited using DC and pulsed sputtering.
SiC Epitaxial Growth on Si(100) Substrates Using Carbon Tetrabromide
Authors: Attolini Giovanni , Bosi Matteo , Rossi Francesca , Watts Bernard Enrico , Salviati Giancarlo , Battistig Gábor , Dobos László , Pécz Béla
Published: May 2010

3C-SiC films were grown on Si by VPE using CBr4 as the carbon source, at temperatures ranging between 1100 to 1250°C. XRD, TEM, AFM, and SEM results indicate that the epitaxy proceeds as a 3D growth of uncoalesced islands at low temperature, whereas a continuous layer with hillocks on top is obtained above 1200°C. The shape and faceting of the islands are analyzed by AFM, showing (311) preferred facets.
Low-Temperature, Low-Pressure and Ultrahigh-Rate Growth of Single-Crystalline 3C-SiC on Si Substrate by ULP-CVD Using Organosilane
Authors: Saito Eiji , Filimonov Sergey , Suemitsu Maki
Published: May 2010

Temperature dependence of the growth rate of 3C-SiC(001) films on Si(001) substrates during ultralow-pressure (ULP: ~10-1 Pa) CVD using monomethylsilane has been investigated in detail by using pyrometric interferometry. A novel behavior, i.e. a sharp division of the growth mode into two regimes depending on the growth temperature, has been found to exist. Based on this finding, we have developed a two-step process, which realizes a low-temperature (900 °C), high-rate growth of single-crystalline 3C-SiC film on Si substrates, whose rate of 3 m/h is extremely high for this ULP process.
Further Evidence of Nitrogen Induced Stabilization of 3C-SiC Polytype during Growth from a Si-Ge Liquid Phase
Authors: Kim-Hak Olivier , Lorenzzi Jean , Jegenyes Nikoletta , Ferro Gabriel , Carole Davy , Chaudouët Patrick , Dezellus Olivier , Chaussende Didier , Viala Jean Claude , Brylinski Christian
Published: May 2010

The influence of nitrogen impurity on the stabilization of 3C-SiC polytype has been studied during vapour-liquid-solid (VLS) growth on 6H-SiC(0001) seed with Si-Ge melt. By changing the partial pressure of N2 during growth, it was found that the proportion of 3C-SiC inside the grown material increases with N2 partial pressure. 6H inclusions are only found for high purity (low N2 content) conditions. The possible interactions proposed to explain this effect are divided in two effects: i) lattice parameter modification and ii) surface induced lateral enlargement variation. A combination of both effects is suspected.
Growth of 4H-SiC Crystals on the 8° Off-Axis 6H-SiC Seed by PVT Method
Authors: Tymicki Emil , Grasza Krzysztof , Racka Katarzyna , Raczkiewicz Marcin , Łukasiewicz Tadeusz , Gała Maciej , Kościewicz Kinga , Diduszko Ryszard , Bożek Rafał
Published: May 2010

In this work we present the growth of 4H-SiC crystals (2 inch in diameter) on the 8° off- axis C-face 6H-SiC seeds, inclined toward [11-20] direction. The growth of crystals by physical vapour transport method (PVT) was realized with the open seed backside in the experimental setup with graphite resistive heater. Some of the crystals were doped with cerium in the purpose of the 4H polytype growth stabilization. For Ce-doped crystals the seed backside carbonization process was decreased in comparison with such effect observed in the undoped SiC crystals.
Low Doped 3C-SiC Layers Deposited by the Vapour-Liquid-Solid Mechanism on 6H-SiC Substrates
Authors: Lorenzzi Jean , Zoulis Georgios , Kim-Hak Olivier , Jegenyes Nikoletta , Carole Davy , Cauwet François , Juillaguet Sandrine , Ferro Gabriel , Camassel Jean
Published: May 2010

We report the results of a systematic investigation performed to reduce the residual n-type doping level of the 3C-SiC layers grown by the VLS mechanism on 6H-SiC(0001) on-axis substrate. This new approach, termed “High purity VLS” leads to low doped and low compensated material, which was confirmed by Raman and Low Temperature Photoluminescence spectroscopy. The resultant 3C morphology remains typical of single-domain layers and the n-type doping level could be estimated around 6x1016 cm-3.
Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy
Authors: Zoulis Georgios , Sun Jian Wu , Beshkova Milena , Vasiliauskas Remigijus , Juillaguet Sandrine , Peyre Hervé , Syväjärvi Mikael , Yakimova Rositza , Camassel Jean
Published: May 2010

Both, n-type and p-type 3C-SiC samples grown on 6H-SiC substrates by sublimation epitaxy have been investigated. From low temperature photoluminescence studies, we demonstrate a low level of residual (n and/or p-type) doping with weak compensation, which is confirmed by secondary ion mass spectroscopy in the case of p-type samples.
Properties of 3C-SiC Grown by Sublimation Epitaxy on Different Type of Substrates
Authors: Beshkova Milena , Lorenzzi Jean , Jegenyes Nikoletta , Birch Jens , Syväjärvi Mikael , Ferro Gabriel , Yakimova Rositza
Published: May 2010

3C-SiC layers have been grown by using sublimation epitaxy at a temperature of 2000°C, on different types of on-axis 6H-SiC(0001) substrates. The influence of the type of substrate on the morphology of the layers investigated by Atomic Force Microscopy (AFM) is discussed. Stacking faults are studied by reciprocal space map (RSM) which shows that double positions domains exists.
Characterization of the Excess Carrier Lifetime of As-Grown and Electron Irradiated Epitaxial p-Type 4H-SiC Layers by the Microwave Photoconductivity Decay Method
Authors: Matsushita Yoshinori , Kato Masashi , Ichimura Masaya , Hatayama Tomoaki , Ohshima Takeshi
Published: May 2010

We measured the excess carrier lifetimes in as-grown and electron irradiated p-type 4H-SiC epitaxial layers with the microwave photoconductivity decay (-PCD) method. The carrier lifetime becomes longer with excitation density for the as-grown epilayer. This dependence suggests that e ≥h for the dominant recombination center, where e andh are capture cross sections for electrons and holes, respectively. In contrast, the carrier lifetime does not depend on the excitation density for the sample irradiated with electrons at an energy of 160 keV and a dose of 1×1017 cm-2. This may be due to the fact that recombination centers with e <<h were introduced by the electron irradiation or due to the fact that the acceptor concentration was decreased significantly by the irradiation.
CL/EBIC-SEM Techniques for Evaluation of Impact of Crystallographic Defects on Carrier Lifetime in 4H-SiC Epitaxial Layers
Authors: Maximenko Serguei I. , Freitas Jaime A. , Picard Yoosuf N. , Klein Paul B. , Myers-Ward Rachael L. , Lew Kok Keong , Muzykov Peter G. , Gaskill D. Kurt , Eddy Charles R. , Sudarshan Tangali S.
Published: May 2010

The effect of various types of in-grown stacking faults and threading screw/edge type dislocations on carrier lifetime and diffusion lengths in 4H-SiC epitaxial films was investigated through cathodoluminescence decays and charge collection efficiencies of electron beam induced current signals at specific defects sites. Most stacking faults yielded ~40% reduction in the carrier lifetime. Moreover, drastic lifetime reductions were observed in regions containing surface triangular defects and bulk 3C polytype inclusions. Dislocations of both types serve as efficient recombination centers, though stronger reduction in diffusion lengths was observed in the vicinity of screw type dislocations.
Nonequilibrium Carrier Recombination in Highly Excited Bulk SiC Crystals
Authors: Jarašiūnas Kęstutis , Ščajev Patrik , Gudelis Vytautas , Klein Paul B. , Kato Masashi
Published: May 2010

We applied time-resolved free carrier absorption (FCA) to monitor non-equilibrium carrier dynamics in 4H epilayers and 3C SiC bulk crystals at excess carrier densities in the N = 1017 - 1019 cm-3 range. The numerical fitting of FCA decay kinetics provided the linear and nonlinear carrier recombination rates in the 40-390 K range and the absorption cross-sections eh at 1064 nm. In 4H, the decrease of the bulk lifetime (800 ns) with excitation provided the bimolecular and Auger coefficients B=(1.2±0.4)×10-12 cm3/s and C=(7±4)×10-31cm6/s, respectively, at room temperature. These values for 3C were 55-150 ns, (2.0±0.4)×10-12 cm3/s, and (2±1)×10-32 cm6/s, respectively. The rate of linear and nonlinear recombination increased at lower temperatures. A value of eh =4.4×10-18 cm2 for 3C SiC at 1.064 m was found 2.3 times smaller than that for 4H SiC.
On the Correlation of the Structural Perfection and Nonequilibrium Carrier Parameters in 3C SiC Heterostructures
Authors: Kadys Arunas , Ščajev Patrik , Manolis Georgios , Gudelis Vytautas , Jarašiūnas Kęstutis , Abramov Pavel L. , Lebedev Sergey P. , Lebedev Alexander A.
Published: May 2010

Photoelectric properties of 3C sublimation-grown epitaxial layers with different structural quality were studied by using time-resolved picosecond transient grating and free carrier absorption techniques. The layer quality was described by a parameter LTW which gives the total length of twin boundaries in a layer. Optical measurements of diffusion coefficients and carrier lifetimes in wide excess carrier density (N >1018 cm-3) and temperature range (10 K to 300 K) revealed the twin defect density dependent ambipolar mobility value at RT as well as essentially different temperature dependences of mobility of the layers. The larger value of absorption cross section in more defective layer at 1064 nm wavelength pointed out to contribution of defect-assisted absorption, which gradually vanished after the filling defect states by free carriers.
Fundamental Band Edge Absorption in 3C-SiC: Phonon Absorption Assisted Transitions
Authors: Grivickas Vytautas , Gulbinas K. , Grivickas Paulius , Manolis Georgios , Linnros Jan
Published: May 2010

An alternative approach based on non-equilibrium free-carrier density measurements was used to characterize the fundamental absorption edge of 3C-SiC at room and 77 K temperatures. At 77 K temperature the extracted absorption edge compared well to the previous literature data revealing characteristic thresholds due to the phonon emission assisted transitions. At room temperature the absorption tail due to the phonon absorption assisted transition was revealed up to the value of 0.01 cm-1 exceeding the previous 5 cm-1 limit induced by unintentional sample doping.
Polytypism Study in SiC Epilayers Using Electron Backscatter Diffraction
Authors: Kościewicz Kinga , Strupiński Wlodek , Wierzchowski Wojciech , Wieteska Krzysztof , Olszyna Andrzej Roman
Published: May 2010

The electron backscatter diffraction (EBSD) detector placed inside a commercial scanning electron microscope (SEM) has been used to study of different SiC polytypes. Different growth conditions in chemical vapor deposition (CVD) method were applied to obtain the 3C- and 4H-SiC polytypes epitaxial layers. Growth processes were conducted on the Si-face on-axis 4H-SiC substrates. The growth temperature was in the range of 1300-1620°C and the reactor pressure was 75mbar. The initial C/Si ratio was varied from 0.075 reaching final value of 1.8. It was observed that intentional ramping of the C/Si ratio at the first stage of the growth clearly influences the 4H/3C factor. The growth temperature and ramping of the C/Si ratio were the main parameters to achieve a homogeneous 3C and 4H-SiC epitaxial layers.
Raman Characterization of Doped 3C-SiC/Si for Different Silicon Substrates and C/Si Ratios
Authors: Piluso Nicolò , Severino Andrea , Camarda Massimo , Anzalone Ruggero , Canino Andrea , Condorelli Giuseppe , Abbondanza Giuseppe , La Via Francesco
Published: May 2010

Raman microscopy has been used to study transport properties in hetero-epitaxial 3C-SiC/Si thin films. By an accurate analysis of the Longitudinal Optic phonon-plasmon coupled (LOPC) modes in n-type doped 3C-SiC films, free carrier density and mobility has been determined. A study of doped 3C-SiC reveals a strong relationship between the calculated free carrier density and both the C/Si ratio used during the epitaxial process and Silicon substrates orientation on which 3C-SiC thin films were grown (maintaining the N2 gas flow rate). The free carrier density obtained is in the range between 5x1016 cm-3 and 4x1018 cm-3. Epitaxial films grown on (111) Si substrates show a higher free carrier density and a lower dependence on C/Si ratios as compared to films grown on (100) Si substrates.
Determination of the Optical Bandgap of Thin Amorphous (SiC)1-x(AlN)x Films
Authors: Guerra Jorge Andres , Winterstein Anja , Erlenbach Oliver , Gálvez Gonzalo , De Zela Francisco , Weingärtner Roland , Winnacker Albrecht
Published: May 2010

Amorphous wide bandgap semiconductor thin films of the pseudobinary compound (SiC)1-x(AlN)x were grown by radio frequency dual magnetron sputtering on CaF2, MgO and glass substrates. We performed isochronical annealing steps up to 500°C. The optical bandgap is determined for each composition from spectroscopic transmission measurement in two different ways: according to Tauc and using the (αhν)2 plot. The dependence of the optical bandgap on the composition x can be described by Vegard’s empirical law for alloys.
Elastic Properties of Dense Organosilicate Glasses Dependent on the C/Si Ratio
Authors: Knaup Jan M. , Li Han , Vlassak Joost J. , Kaxiras Efthimios
Published: May 2010

Organosilicate glasses (OSG) are of great technological interest as low-k dielectrics.
We use ab initio simulations to analyze the influence of the C/Si ratio in OSG on the density
and elastic properties of pore-free material to gain a detailed understanding of the origins of
these properties in this class of materials. We find that the addition of carbon to amorphous
silica leads to a stiffening of the material by removing the bending degrees of freedom of Si-O-Si
bonds. This transition in mechanisms of stiffness, leads to a distinctly nonlinear behavior of
the bulk and elastic modulus over the C/Si ratio. Experimental results do not contradict our
findings, however dominant pore effects impede conclusive comparison.
In-Grown Stacking Faults Identified in 4H-SiC Epilayers Grown at High Growth Rate
Authors: Feng Gan , Suda Jun , Kimoto Tsunenobu
Published: May 2010

In-grown stacking faults (IGSFs) in thick 4H-SiC epilayers grown at high growth rates have been characterized by micro-photoluminescence (micro-PL) spectroscopy and its intensity mapping. Strong PL emissions from the IGSFs are observed even at room temperature. Three kinds of IGSFs have been identified in the samples based on the micro-PL spectra. Each IGSF shows the specific PL emission peak located at 460 nm, 480 nm, and 500 nm, respectively. The shapes, distributions, and densities of IGSFs in the epilayers are revealed by the micro-PL intensity mapping. The stacking sequences of three IGSFs have been determined as (4,4), (3,5), and (6,2) in the Zhadonov’s notation, respectively, by high-resolution transmission electron microscopy observations. Three identified IGSFs are then classified as quadruple Shockley SFs, triple Shockley SFs, and double Shockley SFs, respectively, based on the shear formation model.
Observation of Lattice Plane Bending during SiC PVT Bulk Growth Using In Situ High Energy X-Ray Diffraction
Authors: Hock Rainer , Konias Katja , Perdicaro L. , Magerl Andreas , Hens Philip , Wellmann Peter J.
Published: May 2010

We have investigated thermally induced strain in the SiC crystal lattice during physical vapor transport bulk growth. Using high energy x-ray diffraction lattice plane bending was observed in-situ during growth. With increasing growth rate increasing lattice plane bending and, hence, strain was observed. A comparison with numerical modeling of the growth process shows that the latter is related to the heat of crystallization which needs to be dissipated from the crystal growth front. The related temperature gradient as driving force for the dissipation of the heat of crystallization causes lattice plane bending. Optimization of the growth process needs to consider such effects.
Characterization of 100 mm Diameter 4H-Silicon Carbide Crystals with Extremely Low Basal Plane Dislocation Density
Authors: Dudley Michael , Zhang Ning , Zhang Yu , Raghothamachar Balaji , Byrapa Sha Yan , Choi Gloria , Sanchez Edward , Hansen Darren M. , Drachev Roman , Loboda Mark J.
Published: May 2010

Synchrotron White Beam X-ray Topography (SWBXT) studies are presented of basal plane dislocation (BPD) configurations and behavior in a new generation of 100mm diameter, 4H-SiC wafers with extremely low BPD densities (3-4 x 102 cm-2). The conversion of non-screw oriented, glissile BPDs into sessile threading edge dislocations (TEDs) is observed to provide pinning points for the operation of single ended Frank-Read sources. In some regions, once converted TEDs are observed to re-convert back into BPDs in a repetitive process which provides multiple BPD pinning points.
Structural Analysis of Dislocations in Highly Nitrogen-Doped 4H-SiC Substrates
Authors: Katsuno Masakazu , Ohtani Noboru , Nakabayashi Masashi , Fujimoto Tatsuo , Yashiro Hirokatsu , Tsuge Hiroshi , Aigo Takashi , Hoshino Taizo , Hirano Hosei , Ohashi Wataru
Published: May 2010

Dislocations in highly nitrogen-doped (N > 1×1019 cm-3) low-resistivity ( < 10 mcm) 4H-SiC substrates were investigated by photoluminescence imaging, synchrotron X-ray topography, and defect selective etching using molten KOH. The behavior of dislocations is discussed particularly in terms of their glide motion in the presence of a high concentration of nitrogen. The results indicate that nitrogen impurities up to mid 1019 cm-3 concentration do not show any discernible influence on the glide behavior of basal plane dislocations (BPDs) in 4H-SiC crystals grown by physical vapor transport (PVT) method.
Structure of Inclusions in 4° Offcut 4H-SiC Epitaxy
Authors: Mahadik Nadeemullah A. , Stahlbush Robert E. , Qadri Syed B. , Glembocki Orest J. , Alexson Dimitri A. , Myers-Ward Rachael L. , Tedesco Joseph L. , Eddy Charles R. , Gaskill D. Kurt
Published: May 2010

The structure of various inclusions in SiC epitaxial layers grown on 4o offcut substrates was investigated using three advanced techniques. Using micro-Raman spectroscopy, the observed inclusions exhibited a complex structure having either different SiC polytypes like 3C or 6H or they were misoriented 4H-SiC inclusions. The UVPL images showed dislocations and other extended defects around the inclusion-related defects, and strain fields were observed in the x-ray topographs near the defect sites. Spectral UVPL imaging shows features with varying luminescence inside the inclusion related defects which propagate and may cause deformation in the crystalline structure and lead to non-radiative recombination centers within the defect.
Time Sequential Evolutions of Optically-Induced Single Shockley Stacking Faults Formed in 4H-SiC Epitaxial Layers
Authors: Fujimoto Tatsuo , Aigo Takashi , Nakabayashi Masashi , Satoh S. , Katsuno Masakazu , Tsuge Hiroshi , Yashiro Hirokatsu , Hirano Hosei , Hoshino Taizo , Ohashi Wataru
Published: May 2010

Time-dependent evolutions of single and quadruple Shockley stacking faults (sSSF and 4SSF) in 4° off 4H-SiC epitaxial layers have been investigated. UV illuminations using an Hg-Xe lamp light source generate dissociations of basal plane dislocations (BPDs) into sSSFs whereas for 4SSFs no significant changes in shape occur. Detailed analyses of Photo-luminescence (PL) signals suggest that Si- and C-core partials have different PL spectrum distributions in the wavelength range larger than 750 nm, giving rise to images with different contrasts in PL mappings.
Influence of Shockley Stacking Fault Generation on Electrical Behavior of 4H-SiC 10 kV MPS Diodes
Authors: Zhang Qing Chun Jon , Agarwal Anant K. , Burk Albert A. , O'Loughlin Michael  J. , Palmour John W. , Stahlbush Robert E. , Scozzie Charles
Published: May 2010

The influence of stacking fault (SF) generation on the reverse blocking characteristics has been investigated on SiC 10 kV, 5 A Merged PiN (MPS) diodes. For the first time, we have observed that the generation of SFs under forward biased stress increases the reverse leakage current. In addition, the presence of a secondary diode formed by the electrical stress was observed and attributed to the breakdown voltage failure on certain devices.
Dislocation Activity in 4H-SiC in the Brittle Domain
Authors: Demenet Jean Luc , Amer Madyan , Mussi Alexandre , Rabier Jacques
Published: May 2010

Results of deformation experiments on 4H-SiC single crystals below the usual brittle to ductile transition temperature are reported and discussed in comparison of previous literature data. Si-core and C-core partials are evidenced in the basal plane, and perfect dislocations are also observed on other crystallographic planes. These results could indicate that dislocation activity under high stress is more complex than expected.
Correlation between Leakage Current and Stacking Fault Density of p-n Diodes Fabricated on 3C-SiC
Authors: Kawahara Takamitsu , Hatta Naoki , Yagi Kuniaki , Uchida Hidetsugu , Kobayashi Motoki , Abe Masayuki , Nagasawa Hiroyuki , Zippelius Bernd , Pensl Gerhard
Published: May 2010

The correlation between leakage current and stacking fault (SF) density in p-n diodes fabricated on 3C-SiC homo-epitaxial layer is investigated. The leakage current density at reverse bias strongly depends on the SF density; an increase of one order of magnitude in the SF density enhances the leakage current by five orders of magnitude at a reverse bias of 400 V. In order to obtain commercially suitable MOSFETs with 10-4Acm-2 at 600V, the SF density has to be reduced below 6×104 cm-2. Photoemission caused by hot electrons, which travel along a leakage path, can be observed at the crossing between a SF and the edge of p-well region; where the maximum electric field is induced. The mechanism of the leakage current is discussed in detail in a separate paper.
6H-Type Zigzag Faults in Low-Doped 4H-SiC Epitaxial Layers
Authors: Robert Teddy , Marinova Maya , Juillaguet Sandrine , Henry Anne , Polychroniadis Efstathios K. , Camassel Jean
Published: May 2010

A new type of 6H zigzag faults has been identified from high resolution transmission electron microscopy (HRTEM) measurements performed on low-doped 4H-SiC homoepitaxial layer grown on off-axis substrates in a hot-wall CVD reactor. They are made of half unit cells of 6H with corresponding low temperature photoluminescence (LTPL) response ranging from about 3 eV to 2.5 eV at liquid helium temperature.
Characterization of Surface Defects of Highly N-Doped 4H-SiC Substrates that Produce Dislocations in the Epitaxial Layer
Authors: Ishikawa Yukari , Sugawara Yoshihiro , Saitoh Hiroaki , Danno Katsunori , Kawai Yoichiro , Shibata Noriyoshi , Hirayama Tsukasa , Ikuhara Yuichi
Published: May 2010

The structures of defects that form different types of etch pits on highly N-doped 4H-SiC substrates, that were produced by a sublimation method, after molten KOH etching were characterized. It was found that most of the dislocations in the epitaxial layer originated from defects at the surface of substrate whose etch pit structures were clearly different from the conventional structures. The etch pits were classified into drop, oval, round and caterpillar pits. The drop and oval pits were concluded to be formed by the deformation of conventional etch pits. Round pits were concluded to originate from half loop dislocations and were transformed to complex dislocations by epitaxial growth. Analysis by transmission electron microscopy measurement indicates that slipped edge dislocations (or screw dislocations) on the basal plane form caterpillar pits.
Raman Investigation of Different Polytypes in SiC Thin Films Grown by Solid-Gas Phase Epitaxy on Si (111) and 6H-SiC Substrates
Authors: Wasyluk Joanna , Perova Tatiana S. , Kukushkin Sergey A. , Osipov Andrey V. , Feoktistov Nikolay A. , Grudinkin Sergey A.
Published: May 2010

Raman spectroscopy was applied to investigate a series of SiC films grown on Si and 6H-SiC substrates by a new method of solid gas phase epitaxy. During the growth characteristic voids are formed in Si at the SiC/Si interface. Raman peak position, intensity and linewidth were used to characterize the quality and the polytype structure of the SiC layers. A large enhancement in the peak intensity of the transverse optical and longitudinal optical phonon modes of SiC is observed for the Raman signal measured at the voids. In addition, scanning electron microscopy and atomic force microscopy were used to investigate the surface morphology of SiC layers.
Stacking Faults around the Hetero-Interface Induced by 6H-SiC Polytype Transformation on 3C-SiC with Solution Growth
Authors: Seki Kazuaki , Morimoto Kai , Ujihara Toru , Tokunaga Tomoharu , Sasaki Katsuhiro , Kuroda Kotaro , Takeda Yoshikazu
Published: May 2010

6H-SiC hetero-epitaxially grown on a (111) 3C-SiC was observed with TEM. High-density stacking faults were formed around the hetero-interface, and the density of stacking faults decreased with increasing distance from interface. On the other hand, when 3C-SiC was homo-epitaxially grown on a 3C-SiC, any stacking faults did not exist at the interface between the grown crystal and the seed crystal. Thus, the stacking faults formation started from the 6H/3C hetero-interface. Considering the lattice-mismatch strain between 3C-SiC and 6H-SiC, the strain energy is equivalent to the stacking fault energy of 6H-SiC. This similarity suggests that the stacking faults formation could be caused by the relaxation of the lattice-mismatch strain.
The Influence of the Temperature Gradient on the Defect Structure of 3C-SiC Grown Heteroepitaxially on 6H-SiC by Sublimation Epitaxy
Authors: Marinova Maya , Mantzari Alkyoni , Beshkova Milena , Syväjärvi Mikael , Yakimova Rositza , Polychroniadis Efstathios K.
Published: May 2010

In the present work the structural quality of 3C-SiC layers grown by sublimation epitaxy is studied by means of conventional and high resolution transmission electron microscopy. The layers were grown on Si-face 6H-SiC nominally on-axis substrates at a temperature of 2000°C and different temperature gradients, ranging from 5 to 8 °C /mm. The influence of the temperature gradient on the structural quality of the layers is discussed. The formation of specific twin complexes and conditions for lower stacking fault density are investigated.
TEM and LTPL Investigations of 3C-SiC Layers Grown by LPE on (100) and (111) 3C-SiC Seeds
Authors: Marinova Maya , Zoulis Georgios , Robert Teddy , Mercier Frédéric , Mantzari Alkyoni , Galben-Sandulache Irina G. , Kim-Hak Olivier , Lorenzzi Jean , Juillaguet Sandrine , Chaussende Didier , Ferro Gabriel , Camassel Jean , Polychroniadis Efstathios K.
Published: May 2010

In the present work the defects appearing in layers grown by liquid phase epitaxy on different substrates are compared. The used seeds were (i) 3C-SiC with (111) orientation, grown heteroepitaxially on (0001) 4H-SiC or 6H-SiC substrates by continuous feed physical vapour transport process and the vapour-liquid-solid mechanism, respectively, and (ii) 3C-SiC wafer with (100) orientation from HOYA. The structural and optical investigation showed that (i) on the (111) substrates, due to the appearance of silicon and 6H-SiC inclusions, a layer which consisted of a sequence of long period polytypes was formed. The dominant polytype formed was 21R-SiC, which after successive transformation to 39R- and 57R- SiC led to the formation of 6H-SiC on the top of the layer. (ii) On the (100) substrates, a 3C-SiC layer with comparatively uniform defect density was formed. The main defects were stacking faults and their density was reducing during the process.
Theory of Neutral Divacancy in SiC: A Defect for Spintronics
Authors: Gali Adam , Gällström Andreas , Son Nguyen Tien , Janzén Erik
Published: May 2010

We investigate the neutral divacancy in SiC by means of first principles calculations and group theory analysis. We identify the nature of the PL transitions associated with this defect. We show that how the spin state may be manipulated optically in this defect.
The Carbon Vacancy Related EI4 Defect in 4H-SiC
Authors: Son Nguyen Tien , Carlsson Patrick , Isoya Junichi , Morishita Norio , Ohshima Takeshi , Magnusson Björn , Janzén Erik
Published: May 2010

Electron paramagnetic resonance (EPR) was used to study high-purity semi-insulating 4H-SiC irradiated with 2 MeV electrons at room temperature. The EPR signal of the EI4 defect was found to be dominating in samples irradiated and annealed at ~750°C. Additional large-splitting 29Si hyperfine (hf) lines and also other 13C and 29Si hf structures were observed. Based on the observed hf structures and annealing behaviour, the complex between a negative carbon vacancy-carbon antisite pair (VCCSi–) and a distance positive carbon vacancy ( ) is tentatively proposed as a possible model for the EI4 defect.
Fine Structure of Triplet Centers in Room Temperature Irradiated 6H-SiC
Authors: Scholle Andreas , Greulich-Weber Siegmund , Rauls Eva , Schmidt Wolf Gero , Gerstmann Uwe
Published: May 2010

In non-annealed 6H-SiC samples that were electron irradiated at room temperature, a new EPR signal due to a S=1 defect center with exceptionally large zero-field splitting (D = +652•10-4 cm-1) has been observed under illumination. A positive sign of D demonstrates that the spin-orbit contribution to the zero-field splitting exceeds by far that of the spin-spin interaction. A principal axis of the fine structure tilted by 59° against the crystal c-axis as well as the exceptionally high zero-field splitting D can be qualitatively understood by the occurrence of additional close-lying defect levels in defect clusters resulting in comparatively large second-order spin-orbit coup¬ling. A tentative assignment to vacancy clusters is supported by the observed annealing behavior.