An Ion Assisted Evaporation Technique for Use in the Fabrication of Semiconductor Devices

A conventional thermal evaporator is modified to achieve high performance ohmic contacts to GaAs and InP. With this technique, the evaporated beam is partly ionised, accelerated towards the semiconductor and the ionised portion implanted into the near-surface region. The consequences of this are a breakdown of the natural surface oxide and the premixing of the contact alloy with the semiconductor. Experiments using AuGe/GaAs ohmic contacts show specific contact resistances two orders of magnitude lower than with conventional thermal evaporation.