Papers by Keyword: GTO

Abstract: An investigation into the increased leakage currents and reduced blocking voltages associated with 1450°C lifetime enhancement oxidation for the 4H-SiC p-GTOs is presented. Roughening of the 4H-SiC surface due to localized crystallization of SiO₂, or crystobalite formation, during the high temperature oxidation was identified as one of the main causes of this issue. A factor of 30 difference in permeability to O₂ between amorphous SiO₂ and crystobalite caused uneven oxidation, which resulted in significant roughness. This roughness, placed at the metallurgical junction between the gate and the drift layer, where the E-field is greatest, is believed to be responsible for the premature breakdown characteristics. A 2-step lifetime enhancement process, which moves this roughness to the lower E-field region of the device was introduced to alleviate this issue. A 15 kV 4H-SiC p-GTO with the 2-step lifetime enhancement process demonstrated a significant reduction in V_F over the 1300°C oxidized devices, without any impact on blocking characteristics.

Abstract: High Speed Rail (HSR) is expanding rapidly in the whole world in this decade. Almost all the high-speed trains are fed by high-voltage AC and are equipped with several large motors. In addition, High-speed trains have a strict restriction for both mass and size. Thus, HSR needs power semiconductors that can handle high-voltage and giant current. In addition, EMC problems become larger in these days, thus higher speed of switching is expected. From simple silicon diodes in 1960s, thyristors, GTO thyristors, IGBTs and until new wide gap devices such like SiC, the progress of power semiconductor and cooling system directly pulls the performance of high-speed rolling stock. In some cases, fixed installations for HSR are equipped with flexible AC transmission systems (FACTS) such as static VAR compensators (SVC), also.

Abstract: Advanced high-voltage (≥10 kV) silicon carbide (SiC) devices described in this paper have the potential to significantly impact the system size, weight, high-temperature reliability, and cost of modern variable-speed medium-voltage (MV) systems such as variable speed (VSD) drives for electric motors, integration of renewable energy including energy storage, micro-grids, traction control, and compact pulsed power systems. In this paper, we review the current status of the development of 10 kV-20 kV class power devices in SiC, including MOSFETs, JBS diodes, IGBTs, GTO thyristors, and PiN diodes at Cree. Advantages and weakness of each device are discussed and compared. A strategy for high-voltage SiC power device development is proposed.

Abstract: A growing demand for smart and flexible photovoltaic power conversion and pulsed-power systems is leading to rapid development and commercialization of medium voltage 6.5 - 24 kV, wide-bang gap rectifiers and switches. Conventional silicon bipolar switches are limited to roughly 8 kV breakdown voltages and scaling up the voltage rating requires very thick wafers presenting significant manufacturing challenges. Very thick drift layers of silicon devices also translate into a very high minority carrier charge injected during forward conduction for an efficient conductivity modulation, hence leading to an extremely slow switching speed and poor efficiency. In this paper USCi presents the development of 6.5 kV 4H-SiC gate-turn-off thyristors (GTOs) with multiple floating guard-ring edge termination, and describes their application in an AC-link grid-tied solar inverter system.

Abstract: In this paper, we report our recently developed 1 cm², 15 kV SiC p-GTO with an extremely low differential on-resistance (_RON,diff) of 4.08 mΩ•cm² at a high injection-current density (J_AK) of 600 ~ 710 A/cm². The 15 kV SiC p-GTO was built on a 120 μm, 2×10¹⁴/cm³ doped p-type SiC drift layer with a device active area of 0.521 cm². Forward conduction of the 15 kV SiC p-GTO was characterized at 20°C and 200°C. Over this temperature range, the R_ON,diff at J_AK of 600 ~ 710 A/cm² decreased from 4.08 mΩ•cm² at 20°C to 3.45 mΩ•cm² at J_AK of 600 ~ 680 A/cm² at 200°C. The gate to cathode blocking voltage (V_GK) was measured using a customized high-voltage test set-up. The leakage current at a V_GK of 15 kV were measured 0.25 µA and 0.41 µA at 20°C and 200°C respectively.

Abstract: In this paper we highlight our latest results on high voltage SiC thyristors comprising an etched JTE. Compared to our previous design concepts, the thyristors described here are larger in size and have been investigated regarding pulsed power applications. Quasi-static on-state characteristics show that the devices withstand a repetitive current load of up to 16 A corresponding to a current density of 825 A/cm². Their switching behavior was evaluated up to 1000 V demonstrating characteristic waveforms at turn-on and gate turn-off. Moreover, pulsed current characteristics show that the typical device under test sustained a current pulse of 20 μs with a peak value of 200 A and 10 kA/cm², respectively.

Abstract: In this paper, we report a 0.1cm² 4H-SiC gate-turn-off (GTO) thyristor with 6 kV blocking voltage fabricated on a structure with a 60µm blocking layer. A relatively large area, high voltage 4H-SiC GTO that exhibits encouraging characteristic at the on- and off-states, and a low leakage current with 63% devices blocking 3kV or higher. Initial pulse testing result shows that the fabricated GTOs are capable of both high current density and high turn-off speed.

Abstract: This paper presents results attained with SiC GTO thyristors terminated by a single step and a graded etched JTE. The comparison of both types of devices reveals no significant difference in the on-state and switching characteristics but a higher blocking capability of some thyristors with the latter kind of termination. The best devices showed a forward breakdown voltage of nearly 6 kV, which is a distinct progress as against previous results of thyristors with a graded etched JTE. Furthermore, such GTO thyristors have been characterized dynamically for the first time.

Abstract: In this paper, for the first time, we report 12 kV, 1 cm² SiC GTOs demonstrated with a novel negative bevel termination, which improves the breakdown voltage by >3.5 kV compared to the conventional multiple-zone Junction Termination Extension (JTE). The significant improvement in the blocking voltage was attributed to the elimination of the electrical field crowding in the periphery of the mesa with conventional JTE termination. This new termination has been used in both electrically and optically triggered SiC GTOs. An ultrafast turn-on speed of 70 ns has been measured on 12 kV, 1 cm² SiC light triggered GTOs.

Abstract: IGCT is a kind of new type power electronic device which developed from GTO and IGBT . In this paper, Author based on analysis of the internal structure of GTO, shows how GTO development IGCT through technical methods.Through simulation of its off and on performance, the work curve and comparing results of the two devices are given. Then on two components of the inverter circuits are analyzed and compared. Thinking in large power AC drive locomotive, IGCT inverter is greatly simplifier than GTO inverter circuit, and superior performance,it will become the main converter for AC driving locomotive.