Formation of Ge/Cu ohmic contacts to n-GaAs with atomic hydrogen pre-annealing step

摘要

The work investigated the formation processes of Ge/Cu ohmic contacts to n-GaAs with a germanium content of 30-55% in the film. A comparative analysis was undertaken of the influence of the conditions of a first preliminary annealing carried out in situ with the metallization deposition process, on the value of the specific contact resistance obtained after a second annealing carried out ex situ in a nitrogen environment. It was shown that when the first preliminary annealing is carried out in a flow of atomic hydrogen with a flow density of atoms of 10~(13)-10~(16) at. cm~2 s~(-1) a reduction in specific contact resistance of 2-2.5 times is observed, and also a more homogeneous metallization is formed with a finer microcrystal structure, in comparison with when the first, preliminary annealing is carried out under vacuum. The reduction in specific contact resistance is apparently connected with the action of the hydrogen atoms which minimise the rate of the oxidizing reactions and activate solid phase reactions forming the ohmic contact during the thermal treatment process.