Electrical Control of Magnetoresistance in Highly Insulating Co-Doped ZnO

Abstract

A Zn0.96Co0.04O film with low electron concentration (about 1.5 ×1017 cm-3 at 21 K) on a highly conducting Zn0.99Al0.01O layer has been deposited on a-plane sapphire substrate by pulsed laser deposition. To study the magnetoresistance (MR) of depleted, highly insulating Co-doped ZnO an Au ohmic contact and Pd Schottky contact were deposited on the Zn0.99Al0.01O and Zn0.96Co0.04O layer, respectively. Positive MR of 30% with a current of 10-6 A was observed at 5 K. The positive MR decreases drastically at 5 K and changes to negative MR at 50 K with increasing current, which is considered to be due to the bias voltage control of the electron concentration in the Zn0.96Co0.04O layer. Our work demonstrates the electrically controllable magnetotransport behavior in insulating ZnO-based diluted magnetic semiconductors.