Nickel In Ohmic Contacts To Indium Phosphide

A study of NiAuGe contacts to InP has been undertaken. Various cleaning procedures, metalisation combinations and heat treatments have been investigated. During electrical optimisation and subsequent physical analysis the importance of Ni in the NiAuGe contact to InP became apparent. Major differences between the GaAs/NiAuGe and InP/NiAuGe contacts are suggested. TEM micrographs, for the InP system, show an ordered layer structure of constituent phases. These observations are confirmed by RBS results and also agree with other investigations. The most important observations are those associated with nickel and its role during the formation of ohmic contacts to InP. Nickel was found to form ohmic contacts in a similar manner to the ohmic metalisation NiAuGe. As the alloying temperature was increased to the optimum of 450°C, the effective barrier height was initially observed to increase, then above 350°C to fall as the contact became ohmic. NixPy phases are responsible for ohmic behaviour similar to those observered in the NiAuGe ohmic contact.