Magnetic, electrical and surface morphological characterization of AuGe/Ni/Au Ohmic contact metallization on GaAs/AlGaAs multilayer structures

A process issue arising from the use of ferromagnetic Nickel in the AuGe/Ni/Au Ohmic contact metallization is studied in the context of magnetic field sensors and HEMT devices made using GaAs/AlGaAs multilayer structures with the two dimensional electron gas layer. The dependence of magnetization, contact resistance, adhesion, surface roughness and current distribution of alloyed Ohmic contacts on parameters such as Ni layer thickness, anneal temperature and Au-Ge alloy composition are discussed. The magnetization measurements provided some new and interesting insights into changes occurring in the metallization layers prior to alloying.