Electrical properties of laser annealed AuGe/GaAs ohmic contacts

Abstract
Contact resistivity measurements of laser annealed AuGe/GaAs ohmic contacts as a function of depth (contact resistivity profiling) has shown a monotonically increasing contact resistivity profile for energy densities lower than 2.12 J/cm2. For energy densities higher than 2.12 J/cm2 a minimum in the profiles was observed at a depth of 1200 Å. This suggests that minima previously observed in the variation of contact resistivity as a function of laser energy density are due to a surface phenomenon. These profiles further show that ohmic contacts can be made to GaAs by deposition of metal films on GaAs surfaces from which laser annealed AuGe films have been removed. Contact resistivities as low as 1×10−6 Ω cm2 were obtained even when metal was deposited on GaAs etched to a depth of 1000 Å. Secondary ion mass spectroscopy profiles are included which allow the redistribution of Ge into GaAs to be compared with these contact resistivity profiles.

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