High-electron-mobility ZnO/ZnMgO field-effect transistors and their application in biosensing devices

Abstract

Using c-axis-oriented single-crystalline ZnO/Zn_1-xMg_xO heterostructures grown on a-plane sapphire substrates by molecular beam epitaxy, the formation of a two-dimensional electron gas (2DEG) with high electron mobility at the heterointerface is analyzed. The 2DEG was found to be accumulated by an internal electric field induced predominantly by the difference in spontaneous polarization between the two adjacent oxides. We applied the 2DEG to a top-gate field-effect transistor with an amine-modified Zn_1-xMg_xO gate insulation layer, and demonstrated an amperometric operation in an ion-sensitive device suitable for biosensing applications.