Over Kilovolt GaN Vertical Super-Junction Trench MOSFET: Approach for Device Design and Optimization

In this work, the fundamental concept of P/N-junction for voltage sustaining was introduced in GaN vertical device to push the BV of the device beyond kilovolts. Accordingly, a novel GaN vertical super-junction (SJ) trench MOSFET was proposed and studied by TCAD simulation. In order to realize the typical gradient doping transition stack of P+/P/N
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in conventional Si-SJ structure, the P-GaN/UID-GaN/N
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-GaN stack, where the top P-GaN and bottom N
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-GaN act as the field-stop (FS) layer, is employed avoiding using the hardly achievable high quality P
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-GaN. In order to mitigate the premature punch-through in the top P-GaN/N-drift junction due to the possible under design of the P-GaN thickness or the avalanche breakdown triggered by the high E-field due to the possible under design of the UID-GaN thickness, the device design scheme by obtaining a uniform E-field distribution at the P-GaN/UID-GaN/N
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-GaN to N-drift region interface is proposed. By optimizing the thickness ratio of P-GaN to UID-GaN, the balance between the top punch-through and bottom avalanche can be obtained, which enables achieving the maximum overall BV of the GaN SJ-MOS with a given total thickness of N-GaN drift region. The proposed device structure and the methodology of device design are of great interests for GaN vertical device to achieve kilovolts BV for ultra-high power electronics.