Ion beam mixing for ohmic contact formation to n-type GaAs

Ion beam mixing has been used to produce improved contacts to n-type GaAs. Contact metallizations consisting of evaporated layers of 26 nm Ge plus 18 nm Ni have been bombarded with 100 keV Se+ ions over the temperature range 300–723 K followed by 100–150 nm Au evaporation and annealing at 693 K. The specific contact resistance is minimum for a dose of 1 x 1015 Se+ cm−2 at each implant temperature and is also observed to decrease as the implant temperature is increased. Contacts exposed to the ion bombardment have been shown to have much improved surface morphology compared to contacts produced in an identical way but without the ion bombardment.