The Si/Pd(Si,Ge) ohmic contact on n-GaAs

Abstract

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 2×10−6 Ω cm2. A thin (∼15 Å) 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 ∼2×10−6 to 2–4×10−7 Ω cm 2 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 Ω cm2 range after annealing at 400 °C for 50 h.