期刊
MATERIALS
卷 13, 期 21, 页码 -出版社
MDPI
DOI: 10.3390/ma13214740
关键词
GaN; vertical GaN; trench MOS; gate dielectric; breakdown; trapping; reliability
类别
资金
- ECSEL Joint Undertaking (JU) [826392]
- European Union
- project Novel vertical GaN-devices for next generation power conversion, NoveGaN (University of Padova)
- MIUR (Italian Minister for Education) [232/2016]
We propose to use a bilayer insulator (2.5 nm Al2O3 + 35 nm SiO2) as an alternative to a conventional uni-layer Al2O3 (35 nm), for improving the performance and the reliability of GaN-on-Si semi vertical trench MOSFETs. This analysis has been performed on a test vehicle structure for module development, which has a limited OFF-state performance. We demonstrate that devices with the bilayer dielectric present superior reliability characteristics than those with the uni-layer, including: (i) gate leakage two-orders of magnitude lower; (ii) 11 V higher off-state drain breakdown voltage; and (iii) 18 V higher gate-source breakdown voltage. From Weibull slope extractions, the uni-layer shows an extrinsic failure, while the bilayer presents a wear-out mechanism. Extended reliability tests investigate the degradation process, and hot-spots are identified through electroluminescence microscopy. TCAD simulations, in good agreement with measurements, reflect electric field distribution near breakdown for gate and drain stresses, demonstrating a higher electric field during positive gate stress. Furthermore, DC capability of the bilayer and unilayer insulators are found to be comparable for same bias points. Finally, comparison of trapping processes through double pulsed and V-th transient methods confirms that the V-th shifts are similar, despite the additional interface present in the bilayer devices.
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