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Au/Ge/Ni/Au and Pd/Ge/Ti/Au Ohmic Contacts to AlxGa1-xAs/InGaAs (x = 0.75) Pseudomorphic High Electron Mobility Transistor
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- Authors
- Kyoung Jin Choi, Sang Youn Han, Jong-Lam Lee, Jae Kyoung Moon, Min Park, Haecheon Kim
- Issue Date
- 2003-08
- Citation
- Journal of the Korean Physical Society, v.43, no.2, pp.253-258
- ISSN
- 0374-4884
- Publisher
- 한국물리학회 (KPS)
- Language
- English
- Type
- Journal Article
- Abstract
- The optimal Ohmic contact to an AlxGa1-xAs/InGaAs pseudomorphic high-electron-mobility-transistor (PHEMT) structure with a high Al mole fraction (x = 0.75) was developed from comparative studies of Au/Ge/Ni/Au and Pd/Ge/Ti/Au contacts for various etching depths of the cap layer and annealing temperatures. A minimum Ohmic contact resistivity (?갷) of 2.0 × 10-6 廓쨌cm 2 was obtained by annealing (T = 450 °C) Au/Ge/Ni/Au metals deposited on undoped PHEMT substrate. The ?갷 of Au/Ge/Ni/Au increased with the etching depth, but that of Pd/Ge/Ti/Au showed the opposite trend. This was due to deeper penetration of the Au/Ge/Xi/Au contact compared with the Pd/Ge/Ti/Au contact. The penetrating Au reacted with the PHEMT substrate to form Au2Al and Au2Ga, which generated group-III vacancies acting as donors. The device fabricated using the optimal Ohmic contact showed a low knee voltage and a negligible gate leakage current at high gate bias, which are due to the good Ohmic contact and the large conduction band offset between AlGaAs and InGaAs.