Influence of Ohmic Contact Resistance on Transconductance in AlGaN/GaN HEMT

Yoshikazu HIROSE  Akira HONSHIO  Takeshi KAWASHIMA  Motoaki IWAYA  Satoshi KAMIYAMA  Michinobu TSUDA  Hiroshi AMANO  Isamu AKASAKI  

IEICE TRANSACTIONS on Electronics   Vol.E89-C   No.7   pp.1064-1067
Publication Date: 2006/07/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.7.1064
Print ISSN: 0916-8516
Type of Manuscript: Special Section LETTER (Special Section on Heterostructure Microelectronics with TWHM2005)
Category: GaN-Based Devices
AlGaN/GaN HEMT,  contact resistance,  transconductance,  

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The correlation between ohmic contact resistivity (ρc) and transconductance (gm) in AlGaN/GaN high-electron-mobility transistors (HEMTs) was investigated. To characterize ρc precisely, we fabricated a circular transmission line model (c-TLM) pattern adjoined to a field-effect transistor (FET) pattern on an HEMT. By measuring ohmic contact resistance and sheet resistance using the adjoined c-TLM, intrinsic transconductance (gm0), which is not influenced by the source resistance, can be estimated. The gm0 thus obtained is between 179 and 206 mS/mm. Then, it became possible to calculate the correlation between gm and (ρc. We found that ρc should be below 10-5 Ωcm2 for the improvement of gm in AlGaN/GaN HEMT when Rsh 400 Ω/.