The electrical properties were compared for near-noble transition-metal-based ohmic contacts with a M/Zn/M (M=Ni,Pd) sandwiched structure prepared on p-type InP.The minimum contact resistivities of approx7x10~-5 #OMEGA#cm~2 were obtained in both the NiZn and PdZn contacts while the process window for annealing time of the PdZn contacts was much wider than that of the NiZn contacts.From X-ray diffraction and cross-sectional electron microscopic study at the metal/InP interfaces,it was found that ternary compounds such as Ni_2.7InP compounds were not stable at annealing temperatures above 300 degC,which is the primary reason of poor thermal stability of the NiZn contacts while the Pd_2InP compound was stable at such high temperatures.Selection of a suitable base-metal for InP ohmic contacts was also discussed.
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