Characterization of AuGe-based ohmic contacts to n-GaAs fabricated using ion-assisted deposition

摘要

The effects of simultaneously depositing the AuGe metallization on n-GaAs under the influence of low-energy ion bombardment using a novel ion-assisted deposition (IAD) technique have been investigated. Using current-voltage-temperature, deep-level transient spectroscopy and contact resistance measurements, the contacts were compared with conventional contacts that had not been subjected to ion bombardment. Following annealing at 300 degrees C, the IAD contacts exhibited a substantially lower effective barrier height than the conventional contacts (0.34 eV compared with 0.65 eV). The contact resistance of Ni/AuGe n+GaAs contacts, fabricated at doses varying from zero to 5*1015ions/cm2was found to decrease with increasing ion dose. A minimum typical specific contact resistance of 3*10-7Omega cm2was achieved with the contacts which were irradiated with 2.5*1015ions/cm2and annealed at 450 degrees C. This is an order of magnitude lower than the conventional contact resistance as a result of premixing of the contact metal with the semiconductor and the dispersion of the natural surface oxide, causing an increase in the effective area of electrical contact.