Robert Callanan

Cree, North Carolina, United States

Are you Robert Callanan?

Claim your profile

Publications (37)21.52 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: SiC devices are considered to be the next generation power device. This paper discusses thedesign of a Variable Frequency Drive (VFD) using a 6-in-1 power module that employs SiC-DMOSFETs and SiC Schottky Barrier Diodes (SBDs). A 400V class 11kW prototype drive is designed using a 1200V/50A SiC module by Cree. In this paper, power losses of SiC 6-in-1 module are measured and results are compared with an IGBT-based VFD. Analysis shows that SiC drive does not require current derating up to 60 kHz of PWM switching frequency while standard IGBT drive needs significant derating. High dv/dt and voltage reflection effects are important when fast switching devices like SiC are used. This paper explains the design of an optimal output filter.
    No preview · Conference Paper · Sep 2013
  • Robert Callanan · Julius Rice · John Palmour
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the third quadrant operating characteristics (VDS and ID both negative) of Cree's SiC MOSFETs. This work includes information regarding the body diode characteristics, reverse I–V characteristics for various values of positive and negative gate bias, and the need for antiparallel diodes.
    No preview · Conference Paper · Jan 2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present our recent developments in 4H-SiC power DMOSFETs. 4H-SiC DMOSFETs with a room temperature specific on-resistance of 3.7 m Omega-cm(2) with a gate bias of 20 V, and an avalanche voltage of 1550 V with gate shorted to source, was demonstrated. A threshold voltage of 3.5 V was extracted from the power DMOSFET, and a subthreshold swing of 200 mV/dec was measured. The device was successfully scaled to an active area of 0.4 cm(2), and the resulting device showed a drain current of 377 A at a forward voltage drop of 3.8 V at 25 degrees C.
    No preview · Article · May 2012 · Materials Science Forum
  • Anant K. Agarwal · Lin Cheng · Sei-Hyung Ryu · Robert Callanan

    No preview · Article · Jul 2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: DMOSFETs fabricated in 4H-SiC with capabilities for blocking in excess of 1700V and conducting 20A continuous current in the on-state are presented. These SiC DMOSFETs remain functional to temperatures in excess of 225°C, with leakage current at 1700V at 225°C of less than 5 A with VGS = 0V. The DMOSFETs show excellent switching characteristics, with total switching energy of 1.8 to 1.95 mJ over the entire temperature range of testing (25°C to 200°C), when switched from the blocking state at 1200V to conducting at 20A in a clamped inductive load switching circuit. The electrical characteristics are compared to commercially available Si IGBTs rated to 1700V with similar current ratings as the SiC DMOSFET described herein.
    No preview · Article · Mar 2011 · Materials Science Forum
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Silicon carbide (SiC) materials technology has made rapid advances in recent years. While increasing the wafer diameter from 75 mm to 100 mm, the substrate quality has been greatly improved with much reduced defect density, resulting in higher device yields. Cree is poised to increase the wafer diameter to 150 mm in 2012, which will further reduce the cost of SiC devices. SiC Schottky diodes have demonstrated very high reliability in the field and are being extensively used in Switch Mode Power Supplies (SMPS), and solar inverters, and other applications. Cree has also commercially released a 1200 V, 20 A SiC MOSFET which has been used in solar inverter along with SiC Schottky diode to provide an efficiency gain of 2.36%. More recent R&D results at Cree indicate that the on-resistance of the MOSFET can be reduced by 2x, which will further improve performance and reduce cost.
    Preview · Article · Jan 2011 · ECS Transactions
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present our most recent developments in 4H-SiC DMOSFETs. A 4H-SiC DMOSFET with an active area of 0.1 cm 2 showed a specific on-resistance of 3.7 mΩ-cm 2 with a gate bias of 20 V, and an avalanche voltage of 1500 V with gate shorted to source at 25 o C. A threshold voltage of 3.5 V was extracted from the DMOSFET, and a subthreshold swing of 200 mV/dec was measured. The device was successfully scaled to an active area of 0.5 cm 2 , and the resulting device showed a drain current of 377 A at a forward voltage drop of 3.8 V at 25 o C.
    No preview · Article · Jan 2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microgrids with distributed generation sources are critical for reduction of greenhouse gas emissions and imported energy. However, power converters and circuit breakers built with silicon (Si) switches are too bulky and inefficient to be used in the microgrid system. The development of high-voltage power devices based on silicon carbide (SiC) will be a critical component in building the microgrid with distributed and fluctuating sources of power generation. In this paper, the physics and technology of high-voltage (>10 kV) 4H-SiC power devices, namely MOSFETs and insulated gate bipolar transistors are discussed. A detailed review of the current status and future trends in these devices is given with respect to materials growth, device design, and fabrication processing.
    No preview · Article · Jan 2011 · IEEE Transactions on Power Electronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: Junction barrier Schottky (JBS) diodes and MOSFETs fabricated in 4H-SiC are described. These power devices are capable of blocking in excess of 1700 V with leakage currents of less than tens of microamps at temperatures exceeding 175°C and of conducting tens of amps in the on-state. The static on-state and blocking I-V characteristics of each component are presented, along with a comparison to comparably rated Si bipolar PiN diodes and IGBTs. The dynamic performance of the 4H-SiC diodes and MOSFETs is also presented, and a fully functional 10 kW transformer isolated DC-DC power converter operating at 1000V at a switching frequency of 20 kHz is demonstrated.
    No preview · Article · Jan 2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silicon Carbide (SiC) is an extremely attractive material for semiconductor power devices because of its electrical and physical characteristics. This paper describes the benefits of utilizing SiC Super Gate Turn-Off thyristors (SGTO) in pulsed power applications, reviews the current progress and development of SiC GTOs, and presents the static and pulsed characteristics of large area GTOs with high blocking capabilities. The wide pulsed evaluation of the 0.5 cm2 SiC SGTOs has been demonstrated and reported by the Army Research Laboratory (ARL). This paper presents the wide pulsed capabilities of the 1 cm2 SiC SGTOs. The 1 cm2 SiC SGTO devices handled up to twice the peak current of the 0.5 cm2 SiC SGTOs at a 1 ms pulse width. The wide pulsed evaluation of these devices was demonstrated at ARL. ARL evaluated the static and pulsed characteristics of six of these devices. The devices had a forward blocking voltage rating of 9 kV and a trigger requirement of a negative pulse of 1 A to the gate for a millisecond pulse width. These devices were pulsed as high as 3.5 kA at 1 ms, equating to an action rate of 6 × 103 A2 s and a current density of 4.8 kA/cm2, based on the device active area. The narrow pulsed evaluation of this device has been demonstrated by Cree Inc. A peak current of 12.8 kA with a pulse width of 17 μs (corresponding to 12.8 kA/cm2 based on the chip size) was conducted with this device.
    No preview · Article · Oct 2010 · Solid-State Electronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: A Smart Grid with distributed generation is critical for reducing greenhouse gas emissions. However, current power converters and circuit breakers built with silicon switches are very bulky and inefficient, making their use difficult in practical Smart Grid systems. The development of high voltage power devices based on SiC will be a critical development in building a Smart Grid with distributed and fluctuating sources of power generation. In this paper, the physics and technology of high voltage (> 10 kV) 4H-SiC power devices, namely MOSFETs, IGBTs, and GTOs, are discussed. A detailed review of the current status and trends in these devices is given with respect to materials growth, device design, and the potential future ranges for use.
    No preview · Conference Paper · Jul 2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: Power devices fabricated in 4H-SiC are poised to significantly impact the field of power electronics. There has been great interest in SiC as a material in which to fabricate power electronic devices for quite some time based on its very promising fundamental materials properties. However, it has been far more recently that the potential of SiC is being appreciated as a result of the recent advances in material quality, fabrication processes and device design. Based on the high critical breakdown electric field, high bandgap and high thermal conductivity of SiC, systems that are specifically designed to take advantage of these characteristics offer superior power density, lower cooling requirements, and prolonged survivability in adverse conditions when compared to systems fabricated with Si power devices.
    No preview · Article · Jun 2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, for the first time, we report a large area (1 cm(2)) SiC GTO with 9 kV blocking voltage fabricated on 100-mm 4H-SiC substrates with much reduced Basal Plane Dislocation (BPD) density. The static and dynamic characteristics are described. A forward drop of 3.7 V at 100 A (100 A/cm(2)) is measured at 25 degrees C. A slight positive temperature coefficient of the forward drop is present at 300 A/cm(2), indicating the possibility of paralleling multiple devices for higher current capability. The device exhibits extremely low leakage currents at high temperatures. The device has shown fast turn-on time of 53.9 nsec, and similar to 3.5 mu s of turn-off time, respectively. A stable forward voltage drop after electrical stress for >1000 hours has been achieved.
    No preview · Article · Apr 2010 · Materials Science Forum
  • [Show abstract] [Hide abstract]
    ABSTRACT: 4H-SiC Bipolar Junction Transistors (BJTs) and hybrid Darlington Transistors with 10 kV/10 A capability have beep for the first time. The SiC BJT (chip size: 0.75 cm(2) with an active area of 0.336 cm(2)) conducts a collector current of 10 A (similar to 30 A/cm(2)) with a forward voltage drop of 4.0 V (forced current gain beta(forced): 20) corresponding to a specific on-resistance of 130 m Omega center dot cm(2) at 25 C. The DC current gain, [3, at a collector voltage of 15 V is measured to be 28 at a base current of 1 A. Both open emitter breakdown voltage (BV(CBO)) and open base breakdown voltage (BV(CEO)) of similar to 10 kV have been achieved. The 10 kV SiC Darlington transistor pair consists of a 10 A SiC BJT as the output device and a 1 A SiC BJT as the driver. The forward voltage drop of 4.5 V is measured at 10 A of collector current. The DC forced current gain at the collector voltage of 5.0 V was measured to be 440 at room temperature.
    No preview · Article · Apr 2010 · Materials Science Forum
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pulse power systems require power switches to operate at higher speeds and higher temperatures to meet the demand for smaller and higher power density systems. The paper presents the SiC SGTO (super gate turn-off thyristor) designed by SPCO and Cree. The device has superior switching and peak current handling capability and a promising candidate for pulse power applications.
    No preview · Article · Nov 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: 10-kV silicon carbide (SiC) MOSFETs are currently being developed by a number of organizations in the U.S. with prospective applications in high-voltage and high-frequency power-electronic systems. The aim of this paper is to demonstrate the high-frequency and high-temperature capability of 10-kV SiC MOSFETs in the application of a dc/dc boost converter. In this study, 10-kV SiC MOSFET and junction barrier Schottky (JBS) diode were characterized and modeled in SPICE. Following this, a dc/dc boost converter based on a 10-kV 10-A MOSFET and a 10-kV 5-A JBS diode was designed and tested under continuous operation for frequencies up to 25 kHz. The boost converter had an output voltage of 4 kV, an output power of 4 kW, and operated with a junction temperature of 174degC for the SiC MOSFET. The fast-switching speed, low losses, and high-temperature operation capability of 10-kV SiC MOSFETs demonstrated in the dc/dc boost converter make them attractive for high-frequency and high-voltage power-conversion applications.
    No preview · Article · Nov 2009 · IEEE Transactions on Industry Applications
  • [Show abstract] [Hide abstract]
    ABSTRACT: 4H-SiC DMOSFETs designed to conduct up to 20 A and block in excess of 1200 V are described, and a performance comparison with comparably rated Si MOSFETs and IGBTs is presented. The 4H-SiC DMOSFETs show comparable to slightly improved on-state losses compared to the Si IGBTs and significantly improved performance over the Si MOSFET. Leakage currents of the 4H-SiC DMOSFETs are two orders of magnitude lower than those of the Si switches. Gate charge of the 4H-SiC DMOSFET is also reduced compared to the Si switches; moderately as compared to the Si IGBTs and quite significantly compared to the Si MOSFET, and total switching energy losses are 50% to 70% lower than those of the Si switches. The performance advantages in conduction and switching losses of the 4H-SiC DMOSFET permits operation to much higher frequencies and/or at higher junction temperatures than is achievable with the Si counterpart switches.
    No preview · Conference Paper · Oct 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: The characteristics of silicon carbide, 1200 V, 20 A MOSFETs have been described from a user's perspective. DC and dynamic characteristics of SiC MOSFETs have been compared with Si 900 V super junction MOSFET (SJMOSFET), Si 1200 V MOSFET and IGBTs. The advantages of SiC MOSFET are their lower turn-off losses, lower conduction losses and lower gate charge. However, they have low output impedance, low transconductance and low threshold voltage. These factors should be taken into account when designing the gate drive and fault detection circuits. The use of the internal body diode is not recommended for SiC MOSFETs due to its high voltage drop and therefore considerations for choosing the rating of external SiC Schottky diode have been presented. The absence of turn-off current tail results in voltage overshoot and ringing and therefore careful minimization of parasitics in the gate drive and load circuits is required. Finally, the results of reliability tests on SiC MOSFETs have been summarized.
    No preview · Conference Paper · Oct 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: Power devices made on Silicon Carbide (SiC) are expected to offer significant advantages over silicon due to the unique material properties. With the continuing improvement in both material quality (defect density and carrier lifetime) and SiC device fabrication process, SiC power devices are increasingly fabricated with higher blocking rating and larger die size. This paper describes the benefits of using SiC Gate Turn-Off thyristors (GTO) in power electronics, especially for pulse power applications, reviews the development history and the current state of the art, and outlines the future perspective for developing large area GTOs with high blocking voltage of > 10 kV. Experimental results for the state-of-the-art 9 kV, 1 cm<sup>2</sup> SiC GTOs are presented. Static and dynamic characteristics are described. A forward drop of 3.7 V at 100 A (100 A/cm<sup>2</sup>) is measured at 25°C. A slight positive temperature coefficient of the forward drop is present at 300 A/cm<sup>2</sup> indicating the possibility of paralleling multiple devices for higher current capability. The device exhibits extremely low leakage currents at high temperatures. The turn-on delay is found to be a strong function of the gate current, cathode-anode current and voltage. A peak current of 12.8 kA conducted with a pulse width of 17.4 ¿s indicating the superiority of the SiC GTOs for pulse power applications.
    No preview · Conference Paper · Aug 2009
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, for the first time, large area SiC BJTs were fabricated on SiC wafers with reduced Basal Plane Dislocations (BPDs). We have demonstrated: (1) stable performance on 1200 V, 20 A SiC BJTs after long duration of electrical stress at different current densities up to 150 A/cm<sup>2</sup>; (2) a blocking yield of >80% with low leakage current (<20 nA at 1800 V) on 3" wafers along with current gains in a range of 35-40. Both breakthroughs highlight the possibility for SiC BJTs to be commercialized and utilized in power electronics.
    No preview · Conference Paper · Jul 2009