Impact of Interlayer Processing Conditions on the Performance of GaN Light-Emitting Diode with Specific NiOx/Graphene Electrode

详细信息    查看全文

• 作者：S. Chandramohan ; Ji Hye Kang ; Beo Deul Ryu ; Jong Han Yang ; Seongjun Kim ; Hynsoo Kim ; Jong Bae Park ; Taek Yong Kim ; Byung Jin Cho ; Eun-Kyung Suh ; Chang-Hee Hong
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2013
• 出版时间：February 13, 2013
• 年：2013
• 卷：5
• 期：3
• 页码：958-964
• 全文大小：373K
• 年卷期：v.5,no.3(February 13, 2013)
• ISSN：1944-8252

文摘

This paper reports on the evaluation of the impact of introducing interlayers and postmetallization annealing on the graphene/p-GaN ohmic contact formation and performance of associated devices. Current鈥搗oltage characteristics of the graphene/p-GaN contacts with ultrathin Au, Ni, and NiO_x interlayers were studied using transmission line model with circular contact geometry. Direct graphene/p-GaN interface was identified to be highly rectifying and postmetallization annealing improved the contact characteristics as a result of improved adhesion between the graphene and the p-GaN. Ohmic contact formation was realized when interlayer is introduced between the graphene and p-GaN followed by postmetallization annealing. Temperature-dependent I鈥?i>V measurements revealed that the current transport was modified from thermionic field emission for the direct graphene/p-GaN contact to tunneling for the graphene/metal/p-GaN contacts. The tunneling mechanism results from the interfacial reactions that occur between the metal and p-GaN during the postmetallization annealing. InGaN/GaN light-emitting diodes with NiO_x/graphene current spreading electrode offered a forward voltage of 3.16 V comparable to that of its Ni/Au counterpart, but ended up with relatively low light output power. X-ray photoelectron spectroscopy provided evidence for the occurrence of phase transformation in the graphene-encased NiO_x during the postmetallization annealing. The observed low light output is therefore correlated to the phase change induced transmittance loss in the NiO_x/graphene electrode. These findings provide new insights into the behavior of different interlayers under processing conditions that will be useful for the future development of opto-electronic devices with graphene-based electrodes.

Keywords:

graphene; ohmic contact; interlayer; annealing; NiO_x/graphene; light-emitting diode