Electrical passivation by hydrogen of substitutional cobalt in monocrystalline germanium

Abstract

Co has been implanted at 90 keV in n- and p-type germanium wafers and in-diffused using a 5 min thermal anneal at 500 ∘ C . Deep level transient spectroscopy reveals three levels which are considered to be due to substitutional Co impurities. To passivate the electrical levels of substitutional Co, samples were hydrogenated using a DC-plasma for 4 h at 200 ∘ C . For both the n- and p-type material the Co levels have disappeared up to at least 5 μ m beyond the surface. Directly after the plasma treatment different levels due to irradiation damage have been observed, one of which was assigned to the di-vacancy. The irradiation damage related defects disappeared due to a rapid thermal anneal of 1 min at 400 ∘ C . Two electron traps E230 and E270 which were only present in Co-implanted samples after a hydrogenation have been tentatively assigned to cobalt related defect levels.