Silicon Carbide and Related Materials 2009

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Authors: James E. Green, W.S. Loh, J.P.R. David, R.C. Tozer, Stanislav I. Soloviev, Peter M. Sandvik
Abstract: 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.
Authors: Gwiy Sang Chung, Jae Min Jeong
Abstract: 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.
Authors: Mietek Bakowski, Adolf Schöner, Ingemar Petermann, Susan Savage
Abstract: This paper describes a novel design to achieve sensitive and stable performance of an avalanche photodiode based on silicon carbide material. The design includes a field-stopping layer with limited extension, and junction termination, in order to achieve avalanche multiplication only in the central region of the device. Also, sensitivity is increased by the achievement of a rectangular field distribution, and full depletion of the absorption region by the onset of avalanche multiplication. Evaluation of devices produced with this design show that a low leakage current and a sharp and stable avalanche breakdown point around 120V is achieved. Optical responsivity to radiation of wavelength 200 to 400 nm is shown to increase with increasing applied reverse bias, until a factor of 8 increase is achieved at the breakdown voltage.
Authors: Simon Barker, Bing Miao, Daniel Brennan, Konstantin Vassilevski, Nicolas G. Wright, Alton B. Horsfall
Abstract: 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 uni es 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.
Authors: Phillippe Godignon, Iñigo Martin, Gemma Gabriel, Rodrigo Gomez, Marcel Placidi, Rosa Villa
Abstract: 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.
Authors: Jürgen Biela, Mario Schweizer, Stefan Waffler, Benjamin Wrzecionko, Johann Walter Kolar
Abstract: Switching devices based on wide band gap materials as SiC o er a signi cant 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.
Authors: Amita Patil, Xiao An Fu, Mehran Mehregany, Steven Garverick
Abstract: 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.
Authors: Samuel V. Araújo, Benjamin Sahan, Peter Zacharias, Roland Rupp, Xi Zhang
Abstract: Photovoltaic systems have been considered as one of most promising fields of application for SiC semiconductors mainly due to the requirements for very high efficiency values. Several other system aspects like volume and cost may also profit from the interesting characteristics of such innovative devices. One promising example is the vertical JFET, mainly due to its relative structural simplicity. Nevertheless, its inherent normally-on characteristic calls for especially tailored topologies, as some suitable applications for photovoltaic systems will be presented.
Authors: Xiao An Fu, Amita Patil, Te Hao Lee, Steven Garverick, Mehran Mehregany
Abstract: 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.
Authors: James D. Scofield, Joseph Neil Merrett, Jim Richmond, Anant K. Agarwal, Scott Leslie
Abstract: In this paper we report the electrical and thermal performance characteristics of 1200 V, 100 A, 200°C (Tj), SiC MOSFET power modules configured in a dual-switch topology. Each switch-diode pair was populated by 2 x 56 mm2 SiC MOSFETs and 2 x 32 mm2 SiC junction barrier Schottky (JBS) diodes providing the 100 A rating at 200°C. Static and dynamic characterization, over rated temperature and power ranges, highlights the performance potential of this technology for highly efficient drive and power conversion applications. Electrical performance comparisons were also made between SiC power modules and equivalently rated and packaged IGBT modules. Even at a modest Tj=125°C, conduction and dynamic loss evaluation for 20kHz, Id=100A operation demonstrated a significant efficiency advantage (38-43%) over the IGBT components. Initial reliability data also illustrates the potential for SiC technology to provide robust performance in harsh environments.

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