COMPARISON STUDY OF PD/IN/PD, PD-IN/PD, AND PD-IN OHMIC CONTACTS TO N-GAAS

Various deposition structures, Pd/In/Pd, Pd-In/Pd and Pd-In, as ohmic contacts to n-GaAs were investigated. The codeposited contacts, Pd-In/Pd and Pd-In have smooth surfaces, and their minimum specific contact resistances are 3 x 10(-6)Omega-cm(2) after annealing at 600 degrees C for 10 s. X-ray diffraction analysis showed that the phase of codeposited contact was PdIn up to 700 degrees C annealing. The minimum specific contact resistance of layer-deposited contact Pd/In/Pd is 4 x 10(-6) Omega-cm(2) after annealing at 650 degrees C for 10s, however, hollow blisters causing rough surface were created during depositing outer Pd layer. The phases of as-deposited layered contact were Pd and PdIn3, and then the major phase became PdIn after annealing below 500 degrees C with a small amount of PdGa which disappeared after annealing above 500 degrees C. The contact resistances of all contacts increased with time after 400 degrees C aging. Electrical degradation during 400 degrees C aging is mainly correlated with the Ga diffusing through the PdIn layer and accumulating at surface of the contact as exposed by Auger depth profiling analysis.