Formation of low resistance nonalloyed Al/Pt ohmic contacts on n-type ZnO epitaxial layer

We have investigated nonalloyed Al/Pt ohmic contacts on n-type ZnO:Al (nd=2.0×1018 cm−3). It is shown that the as-deposited Al/Pt contacts produce a specific contact resistivity of 1.2×10−5 Ω cm2. Auger electron spectroscopy and x-ray photoelectron spectroscopy depth profile results show interdiffusion between oxygen and aluminum, resulting in an increase of carrier concentrations near the ZnO surface. The increase of the carrier concentration at the surface region of ZnO is attributed to the low resistance of the nonalloyed Al/Pt contact.