Reduction of Ohmic Contact Resistance of Solid Phase Regrowth Contacts to n-InGaAs Using a Sulfur Pretreatment

We report an Ohmic contact to lightly doped (5×10¹⁷ cm^-3) n-In_0.53Ga_0.47As with a specific contact resistance of ρ_c=2.6×10^-8±1.7×10^-8 Ω-cm², rivaling the lowest reported values on n-In_0.53Ga_0.47As with significantly higher original dopant concentrations than the epilayer used in this letter. This reduction of ρc was achieved using the combination of a Pd/Si-based solid phase regrowth (SPR) contact with an ammonium sulfide surface treatment before contact deposition. Transmission electron microscopy confirmed that the SPR mechanism still occurred when the ammonium sulfide treatment was used. Both the SPR and sulfide-treated SPR cases reduced ρ_c versus a Pd/Ti/Au contact. For comparison, a sulfide-treated Pd/Ti/Au contact that does not undergo SPR was fabricated, and it did not have a lower ρ_c compared with the same contact without the sulfide treatment. This discrepancy indicates that SPR is essential for benefiting from the sulfide treatment.