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Detailed Program
Paper Number : LD-I10
Time Frame : 14:20~14:45
Presentation Date : Friday, 28, November
Session Name : LED and Display Materials
Session Chair 1# : Jooonseop Kwak
Session Chair 2# : Yasushi Nanishi
Carrier transport phenomena in sputtered ITO ohmic contacts to p-GaN
Joon Seop Kwak
Sunchon National University
Keywords: ITO, p-GaN, LEDs

High power LEDs have attracted great attention as light sources for general lightings and back-light unit of LCD displays, as well. One of the main concerns in this area is the fabrication of high-quality ohmic contacts to p-GaN with low resistance, and high transparency or reflectivity. Achieving low resistance ohmic contacts to p-GaN has been particularly challenging, because of difficulty in obtaining a hole concentration over 1018 cm-3 and the absence of metals having a work function higher than that of p-GaN. In order to achieve high-quality ohmic contacts to InGaN-based LEDs, carrier transport phenomena at the interface between metal and p-GaN should be elucidated.

This presentation discusses carrier transport phenomena in metal contacts to p-GaN. Especially, based upon the carrier transport phenomena, we will focus on Indium tin oxide (ITO) ohmic contact to p-GaN since ITO is commonly used as a transparent electrode on p-type GaN in LEDs. Because transmittance and specific resistance of ITO film have a significant impact on the efficiency of top emission LEDs, various vacuum deposition methods have been studied to grow a high quality ITO film on p-type GaN. However, due to the plasma damage in ITO sputtering process, e-beam evaporated ITO is widely used to make the top emission LEDs in spite of its relatively low film quality. Although a sputtering process is well known to obtain the best quality of ITO films, it cannot be applied due to the degradation of p-type GaN through the impact of high energy ion or electron in plasma. In this study, the properties of sputtered ITO films grown by plasma damage-free condition will be shown, and the mechanism for forming a low resistance sputtered ITO ohmic contact to p-GaN will also be discussed.
Acknowledgements : This study is financial supported by Basic Science Research Program through the NRF of Korea funded by the Ministry of Education (NRF-2014R1A6A1030419) and the BK21 PLUS program at SCNU.