PdGe-based ohmic contacts to high-low doped n-GaAs with and without undoped cap layer

Abstract

We report the ohmic contact formation mechanism for a low-contact resistance PdGe-based system on high-low doped GaAs with and without undoped cap layer annealed in the temperature range of 380-450°C. The lowest average specific contact resistances of the Pd/Ge/Ti/Pt ohmic contacts with and without undoped cap layer after annealing at 400°C were 5.3×10-6 Ω cm2 and 2.4×10-6 Ω cm2, respectively. And the lowest average specific contact resistances of the Pd/Ge/Ti/Pt/Au ohmic contacts with and without undoped cap layer after annealing at 380°C were 3.5×10-6 Ω cm2 and 3.4×10-6 Ω cm2, respectively. For the Pd/Ge/Ti/Pt contact without undoped cap layer, the x-ray diffraction, cross-sectional scanning electron microscopy and Auger electron spectroscopy were utilized in this study. The Pd/Ge/Ti/Pt ohmic contact without undoped cap layer was thermally stable after isothermal annealing at 400°C for 6 h.