Journal of Materials Science and Engineering with Advanced TechnologyAuthor's: L. S. CHUAH, Z. HASSAN, Y. SIVALINGAM, C. DI. NATALE and C. FALCONI
Pages: [1] - [17]
Received Date: June 3, 2012
Submitted by:
An ohmic contact is required for achieve long lifetime execution of optical and electrical devices. In this study, we are investigate on the structures and properties of titanium(Ti)/aluminium(Al) bi-layer contacts on undoped ZnO nanorod/AlN/Si(111). Firstly, high temperature grown buffer layer AlN (about 200nm) were grown on silicon (111) substrates by radio frequency nitrogen plasma assisted molecular beam epitaxy (PAMBE). Following by undoped ZnO nanorod layers were grown on AlN buffer layer using a hydrothermal approach. All the films were detected to have c-axis (0001) selected orientation adjusted with normal to the substrate surface. The structural and electrical stability of the contacts at thermal treatment (200°C-500°C) were studied, as low resistance metal semiconductor contacts are necessary for high quality electronic devices. Scanning electron microscopy (SEM) is applied to investigate the reformations in the surface morphology properties of the contacts on thermal annealing. The transmission line method (TLM) and current-voltage (I-V) measurements were used to determine the specific contact resistivity. The nonalloyed ohmic contact could be associated to the thermal annealing, which forms nitrogen vacancies that result in a heavily n-type surface whereby generate a tunneling junction. The nonalloyed Ti/Al contact on as-grown ZnO nanorods surfaces reveals non-ohmic behaviour. After alloying at 500°C for 15 min, Ti/Al contacts ZnO nanorods surfaces have specific contact resistances around 0.062. Nonalloyed Ti/Al ohmic contacts would be extraordinarily helpful for fabricating high breakdown, recessed gate field effect transistors on ZnO since the moderate post annealing condition changes only the near surface layer to heavily n-type.
Ti/Al, ohmic, ZnO, thermal annealing.
