Possibility of Reducing The On-resistance in 1 kV-class Lateral Superjunction Power Devices based on III-V Semiconductors

Compared with conventional forward converters, active clamp forward (ACF) converters have many advantages, including lower voltage stress on the primary power devices, the ability to switch at zero voltage, reduced EMI and duty cycle operation above 50%. Thus, it has been the most popular solution for the low bus voltage applications, such as 48 V and 28 V. However, because of the poor performance of Si MOSFETs, the efficiency of active clamp forward converters is difficult to further improved. Focusing on the bus voltage of 28 V with 18~36 V voltage range application, the Gallium Nitride high electron-mobility transistors (GaN HEMT) with ultralow on-resistance, low parasitic capacitances, and no reverse recovery, is incorporated into active clamp forward converters for achieving higher efficiency and power density, in this paper. Meanwhile, the comparative analysis is performed for Si MOSFET and GaN HEMT. In order to demonstrate the feasibility and validity of the proposed solution and comparative analysis, two 18~36 V input, 120 W/12 V output, synchronous rectification prototype with different power devices are built and compared in the lab. The experimental results show the GaN version can achieve the efficiency of 95.45%, which is around 1% higher than its counterpart under the whole load condition and the same power density of 2.2 W/cm3.

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Critical Technical Issues in High Voltage SiC Power Devices

Materials Science Forum ◽

10.4028/www.scientific.net/msf.600-603.895 ◽

2008 ◽

Vol 600-603 ◽

pp. 895-900 ◽

Cited By ~ 14

Author(s):

Anant K. Agarwal ◽

Albert A. Burk ◽

Robert Callanan ◽

Craig Capell ◽

Mrinal K. Das ◽

...

Keyword(s):

Threshold Voltage ◽

Carrier Mobility ◽

Negative Charge ◽

State Of The Art ◽

Power Devices ◽

Power Mosfets ◽

Large Numbers ◽

Technical Issues ◽

The Difference ◽

Difficult Issue

In this paper, we review the state of the art of SiC switches and the technical issues which remain. Specifically, we will review the progress and remaining challenges associated with SiC power MOSFETs and BJTs. The most difficult issue when fabricating MOSFETs has been an excessive variation in threshold voltage from batch to batch. This difficulty arises due to the fact that the threshold voltage is determined by the difference between two large numbers, namely, a large fixed oxide charge and a large negative charge in the interface traps. There may also be some significant charge captured in the bulk traps in SiC and SiO2. The effect of recombination-induced stacking faults (SFs) on majority carrier mobility has been confirmed with 10 kV Merged PN Schottky (MPS) diodes and MOSFETs. The same SFs have been found to be responsible for degradation of BJTs.

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