Experimental demonstration of “Cold” low contact resistivity ohmic contacts on moderately doped n-Ge with in-situ atomic hydrogen clean

Low contact resistivity ohmic contacts are demonstrated on n-Ge at doping level N_D of 1×10¹⁹ cm^-3. Atomic Hydrogen (H*) clean was shown to reduce the specific contact resistivity (ρ_C) by 7% for the first time, due to reduction of barrier height of 70meV compared to the unclean sample. Improvement was primarily due to the reduction of the germanim oxide, GeO_x, and surface passivation at the interface by H atoms as confirmed by energy-dispersive X-ray spectroscopy (EDS). The ρ_C of 2.7×10^-5 Ω-cm², at a moderate doping density of 1×10¹⁹ cm^-3, is the lowest with the minimum possible thermal budget.