ガリウム・ヒ素化合物半導体用の超新機能電極材料の研究

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NiInGe Ohmic contact materials which are attractive to use in the future GaAs devices were developed in our laboratories. Although the NiInGe contacts provided low contact resistances of around 0.3 Ω-mm and excellent thermal stability, further reduction of the contact resistance (Rc) of the NiInGe contacts was mandatory to apply these contacts in the sub-micron devices. In this research project, the microstructural parameters which influence the Rc values were investigated by correlating the Rc values with the microstructure at the interface between the contact materials and GaAs. The Rc values of the NiInGe contacts were found to depend strongly on the volume fraction and the In concentration (x) of the In_xGa_<1-x>As compound semiconductor layers which were formed at the metal/GaAs interface. Both the volume fraction and the In concentration of the In_xGa_<1-x>As layers were found to depend on the thickness of the In layer used in the NiInGe contact and the annealing temperature to form the Ohmic contacts. The Rc value of 0.18 Ω-mm was obtained for the Ni(18nm)/In(13nm)/Ge(30nm) contact after annealing at temperature of around 650 ℃ for 5 s where a slash "/" indicates the deposition sequence.