Ultra low-resistance palladium silicide Ohmic contacts to lightly doped n-InGaAs

Abstract

The formation of shallow, ultra-low resistance, Pd/Si solid-phase regrowth (SPR) ohmic contacts to n-In0.53Ga0.47As epilayers of ND=1×1017 cm−3 and ND=3×1019 cm−3 is demonstrated. The resulting specific contact resistances of 9×10−8 Ω cm2 and 1.8×10−8 Ω cm2, respectively, are the lowest demonstrated for SPR contacts to n-InGaAs. An optimum Pd/Si atomic ratio of 1.5 is found to be essential to achieving low specific contact resistance. A low-temperature, two-step, rapid thermal annealing process has been employed to activate the InGaAs regrowth process and consistently achieve shallow contacts with minimal lateral diffusion. Transmission electron microscopy is used to substantiate the SPR mechanism of contact formation. For lightly doped epilayers, I-V-T measurements from 77–300 K show that the ohmic behavior is a direct result of the SPR process due to the introduction of excess Si dopant greater than 1019 cm−3 at the regrown InGaAs interface.