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학술지 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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Kyoung Jin Choi, Sang Youn Han, Jong-Lam Lee, 문재경, 박민, 김해천
Journal of the Korean Physical Society, v.43 no.2, pp.253-258
한국물리학회 (KPS)
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.
KSP 제안 키워드
Annealing temperature, Au contacts, Cap layer, Conduction band offset, Etching depth, High electron mobility transistor(HEMT), Ohmic contact, comparative study, contact resistivity, gate bias, gate leakage current