New insights into formation of Ni-based alloyed Ohmic contacts to GaAs

Abstract

Magnetic properties of AuGe/Ni/Au Ohmic contact for use in fabrication of high sensitivity Hall magnetic field sensors with integrated FET circuits, utilizing GaAs/AlGaAs 2DEG, are investigated. Measurements indicate that Ni undergoes solid-state, solubility limited dissolution into the AuGe layer during the anneal, and prior to alloying of the metallization structure for the formation of Ohmic contact. This results in increase of the melting temperature of the AuGe layer. The ohmic contact structure is rendered non-magnetic upon annealing and prior to the alloying. Therefore, the conventional process Ohmic contact process can be used for integrating Hall sensors with FET and pHEMT in monolithic form.