Investigations on the Cosputtered ITO-ZnO Transparent Electrode Ohmic Contacts to n-GaN

• Main Authors: Wei-Hua Hsiao, Tai-Hong Chen, Li-Wen Lai, Ching-Ting Lee, Jyun-Yong Li, Hong-Jyun Lin, Nan-Jay Wu, Day-Shan Liu
• Format: Article
• Language: English
• Published: MDPI AG 2016-02-01
• Series: Applied Sciences
• Subjects: cosputtered ITO-ZnO; n-GaN; transparent electrode; Ti interlayer; ohmic contact; figure-of-merit
• Online Access: http://www.mdpi.com/2076-3417/6/2/60

Transparent indium tin oxide (ITO) and cosputtered ITO-zinc oxide (ZnO) films’ contacts to an n-GaN epilayer were investigated. Both of these electrodes’ contact to the n-GaN epilayer showed Schottky behavior, although the contact resistance of the ITO-ZnO/n-GaN system was lower than that of the ITO/n-GaN system. By placing a thin Ti interlayer between the ITO-ZnO/n-GaN interface, nonalloyed ohmic contact was achieved. The inset Ti interlayer was both beneficial both for enhancing the outdiffusion of the nitrogen atoms at the surface of the n-GaN and suppressing the indiffusion of oxygen atoms from the surface of the ITO-ZnO to n-GaN. The figure-of-merit (FOM), evaluated from the specific contact resistance and optical property of the Ti/ITO-ZnO system’s contact to the n-GaN epilayer, was optimized further at an adequate thickness of the Ti interlayer.