Influence of NH3-Plasma Pretreatment before Si3N4 Passivation Film Deposition on Current Collapse in AlGaN/GaN-HEMTs

Shinichi HOSHI  Toshiharu MARUI  Masanori ITOH  Yoshiaki SANO  Shouhei SEKI  

IEICE TRANSACTIONS on Electronics   Vol.E89-C    No.7    pp.1052-1056
Publication Date: 2006/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.7.1052
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Heterostructure Microelectronics with TWHM2005)
Category: GaN-Based Devices
AlGaN/GaN-HEMTs,  current collapse,  Si3N4 passivation film,  NH3-plasma pretreatment,  

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In AlGaN/GaN high electron mobility transistors (HEMTs), Si3N4 passivation film brings effective improvements in the current collapse phenomenon, however, the suppression of this phenomenon in a high voltage operation can not be achieved in only the Si3N4 deposition process. In order to solve this problem, we have demonstrated an NH3-plasma surface pretreatment in the chamber of plasma enhanced chemical vapor deposition (PE-CVD) just before Si3N4 deposition process. We found that the optimized NH3-plasma pretreatment could improve the current collapse as compared with only the Si3N4 deposition and an excessive pretreatment made it worse adversely in AlGaN/GaN-HEMTs. It was confirmed by Auger electron spectroscopy (AES) analysis that the optimized NH3-plasma pretreatment decreased the carbon contamination such as hydrocarbon on the AlGaN surface and the excessive pretreatment degraded the stoicheiometric composition of AlGaN surface.