Materials Science Forum Vols. 821-823

Abstract: Two types of 4H-SiC semiconductor detectors (D1 and D2) are realized based on ion implantation of ¹⁰B inside the aluminum metallic contact. The first detector shows a high leakage current after ¹⁰B implantation and low signal to noise ratio. However, improvements concerning the implantation parameters led to lower leakage current and thus to higher signal to noise ratio. Moreover such detectors show their stability under different thermal neutron fluxes showing the reproducible features of the pulse height spectra and same electrical behaviour before and after irradiation.

Abstract: The thermal management of power module is one of the key important issues for power conversion circuit design. SiC power module is expected to give less conduction and switching loss than conventional Si device, which enables to facilitate the thermal management of a power conversion circuit. This paper develops 2in1 Full-SiC power module and studies the applicability for 600V→300V, 15kW DC-DC buck converter. The feasible thermal design of SiC power module to serve rated operation of the converter circuit is discussed based on the elemental experiments. The developed full-SiC power module realized lower loss and smaller converter circuit than conventional-Si power module.

Abstract: This Paper describes a non-isolated bidirectional full SiC 800V 200kW DCDC-converter power stage for electric and hybrid vehicles that reaches a power density of more than 100 kW/dm3 at a switching frequency of 200 kHz. The high power density is achieved by the use of SiC-MOSFETs sintered on custom made Si₃N₄ DCB-substrates controlled by custom made extremely flat drivers and a resulting very low inductive DC-link connection. All passive components like inductors and capacitor boards are custom made in order to keep all parasitic effects as low as possible. The power is subdivided on six interleaved phases to reduce the required capacitor ripple current capability.

Abstract: Three different turn-off strategies are presented for 6.5 kV class SiC Thyristors. A cathode current of 62 A (284 A/cm²) is successfully turned off by applying a reverse bias of ≈ 30 V to the cathode of a SiC Thyristor. The minimum turn-off time (t_q) for the Thyristor using this forced commutation technique is investigated as a function of cathode current density, reverse gate current and the dV/dt of the re-applied forward (blocking) bias. The Anode Switched Thyristor (AST) turn-off mode is demonstrated at a maximum cathode voltage of 3600 V and 14.5 A (199 A/cm²) of cathode current. A cathode current of 5.5 A (75 A/cm²) is successfully turned off by the gate turn off (GTO) or hard turn-off mode at different temperatures up to 200°C. The high-level lifetime (t_HL) in the thick p-layer is extracted from the hard turn-off waveforms.

Abstract: Optical switch-on of a very high voltage (18-kV class) 4H-SiC thyristor with an amplification step (pilot thyristor) to the current I_max = 1225A has been demonstrated using a purely inductive load. The results obtained show that a further switch-on current increase can only be achieved by introducing additional amplification steps in the pilot thyristor structure.

Abstract: Two versions of Schmitt trigger, an emitter-coupled and an operational amplifier (opamp)-based, are implemented in 4H-SiC bipolar technology and tested up to 500 °C. The former benefits the simplicity, smaller footprint, and fewer number of devices, whereas the latter provides better promise for high temperature applications, thanks to its more stable temperature characteristics. In addition, the measurements in the range 25 °C - 500 °C, shows that the opamp-based version provides negative and positive slew rates of 4.8 V/µs and 8.3 V/µs, ~8 and ~3 times higher than that of the emitter-coupled version, which are 1.7 V/µs and 1 V/µs.

Abstract: The design, fabrication, early testing and material property assessment work related to the development of an opto-mechanical pressure sensor implemented with hetero-epitaxial 3C-SiC on silicon is described. The sensor is constituted by a single-crystal 3C-SiC membrane whose deflection upon pressure application is measured using a fiber-optic interferometric readout. The fabrication of sensor prototypes and micromachined 3C-SiC membranes for test purposes is described and the results of bulge tests on the membranes are reported. Functional characterization of the sensor prototypes in the pressure range 0-3 bar is also presented, showing good linearity and reproducibility of the sensor response, sensitivity of roughly 2 mV/bar and estimated pressure resolution around 0.5 bar on a 0-200 bar dynamic range.

Abstract: In this paper, an improved planar MOS barrier Schottky (PMBS) rectifier is proposed which utilizes the PECVD deposited high-k semi-insulating polycrystalline silicon (SIPOS) as the MOS area gate dielectrics for the first time. By adopting the high-k SIPOS as the MOS gate dielectrics, the peak electric field at the interface betwwen dielectrics layer and SiC can be significantly relieved and the device reliability can obviously enhanced without considerable degradation of on-state characteristics. With the optimized the thickness of the SIPOS film, the breakdown voltage (BV) of 1500V for the fabricated device was achieved, which is approximately corresponds to 85% of the theoretical parallel plane breakdown voltage value calculated from the used epilayer structure. And the specific on-state resistance (R_SP-ON) is about 4.2mΩ•cm². The corresponding figure-of-merit of VB²/ R_SP-ON for the proposed device is 535.7MW/cm².

Abstract: Integrated digital circuits, fabricated in a bipolar SiC technology, have been successfully tested up to 600 °C. Operated with-15 V supply voltage from 27 up to 600 °C OR-NOR gates exhibit stable noise margins of about 1 or 1.5 V depending on the gate design, and increasing delay-power consumption product in the range 100 - 200 nJ. In the same temperature range an oscillation frequency of about 1 MHz is also reported for an 11-stage ring oscillator.

Abstract: We fabricated electrostatically-excited single-crystalline 4H-SiC microcantilever resonators with various thicknesses and lengths. Their resonant characteristics were investigated from room temperature (RT) up to 600°C. The resonant frequency of the cantilevers decreased with increasing temperature. From the results, the temperature dependence of Young’s modulus of single-crystalline 4H-SiC was obtained, i.e., 3% decrement with increasing temperature from RT to 600°C. The cantilevers with different thicknesses showed different temperature dependences of the quality factor. A 2-μm-thick cantilever exhibited a high quality factor (Q) (250,000) at RT and the Q decreased to 6,000 at 600°C, which can be explained by thermoelastic damping. On the other hand, a Q of a 0.45-μm-thick cantilever was still high (50,000) even at 600°C.