Electrical and structural properties of low-resistance Pt/Ag/Au ohmic contacts to p-type GaN

摘要

A Pt (20 nm)/Ag (50 nm)/Au (30 nm) metallization scheme has been investigated for producing low-resistance ohmic contacts to moderately doped p-type GaN (1.3 x 10~(17) cm~(-3)). It is shown that the as-deposited contacts exhibit a linear Ⅰ-Ⅴ characteristic with a specific contact resistance of 4.43 x 10~(-3) Ω cm~2. The Pt/Ag/Au contact produced a specific contact resistance as low as 1.70x 10~(-4) Ω cm~2 after annealing at 800℃ for 1 min in a N_2 atmosphere. It is further shown that the surface morphology of the contact annealed at 800℃ (RMS roughness of 19.9 nm) became somewhat degraded compared with that of the as-deposited one (RMS roughness of 3.3 nm). Based on the Auger electron microscopy and X-ray diffraction results, possible explanations for the improvement of the ohmic behavior are described.