THE SI/PD(SI,GE) OHMIC CONTACT ON N-GAAS

A modified Si/Pd ohmic contact to n-GaAs has been developed based on the solid-phase regrowth mechanism. The Si/Pd contact usually yields a contact resistivity of 2X10(-6) OMEGA-cm-2. A thin (approximately 15 angstrom) layer of additional Ge or Si embedded in the Pd layer of the Si/Pd contact structure is used to reduce the contact resistivity from approximately 2X10(-6) to 2-4X10(-7) OMEGA-cm2 without suffering from a loss of thermal stability. The reduction in the contact resistivity is explained in terms of the formation of an n+ GaAs surface layer via solid-phase regrowth. The modified contacts show uniform surface and interface morphologies. The contact resistivity of the modified contacts remains in the mid-10(-6) OMEGA-cm2 range after annealing at 400-degrees-C for 50 h.