Analysis of Passivation-Film-Induced Stress Effects on Electrical Properties in AlGaN/GaN HEMTs

Naoteru SHIGEKAWA  Suehiro SUGITANI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C   No.8   pp.1212-1217
Publication Date: 2010/08/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.1212
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Heterostructure Microelectronics with TWHM 2009)
Category: GaN-based Devices
Keyword: 
GaN,  HEMT,  threshold voltage,  piezoelectric effects,  film stress,  

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Summary: 
Effects of stress in passivation films on the electrical properties of (0001) AlGaN/GaN HEMTs are numerically analysed in the framework of the edge force model with anisotropical characteristics in elastic properties of group-III nitrides explicitly considered. Practical compressive stresses in passivation films induce negative piezoelectric charges below the gates and bring forth a-few-volt shallower threshold voltages. In addition, the shift in the threshold voltage due to the compressive stress is proportional to LG-1.1-1.5 with gate length LG, which is comparable to the expectation based on the charge balance scheme. These result suggest that passivation films with designed stress might play a crucial role in realising AlGaN/GaN HEMTs with shallow or positive threshold voltages.