Abstract
Pristine graphene and a graphene interlayer inserted between indium tin oxide (ITO) and p-GaN have been analyzed and compared with ITO, which is a typical current spreading layer in lateral GaN LEDs. Beyond a certain current injection, the pristine graphene current spreading layer (CSL) malfunctioned due to Joule heat that originated from the high sheet resistance and low work function of the CSL. However, by combining the graphene and the ITO to improve the sheet resistance, it was found to be possible to solve the malfunctioning phenomenon. Moreover, the light output power of an LED with a graphene interlayer was stronger than that of an LED using ITO or graphene CSL. We were able to identify that the improvement originated from the enhanced current spreading by inspecting the contact and conducting the simulation.
Highlights
Lateral-type GaN-based light-emitting diodes (LEDs) have recently been immensely improved and commercialized for various applications, including general lighting
Pristine graphene and a graphene interlayer inserted between indium tin oxide (ITO) and p-GaN have been analyzed and compared with ITO, which is a typical current spreading layer in lateral GaN LEDs
Beyond a certain current injection, the pristine graphene current spreading layer (CSL) malfunctioned due to Joule heat that originated from the high sheet resistance and low work function of the CSL
Summary
Lateral-type GaN-based light-emitting diodes (LEDs) have recently been immensely improved and commercialized for various applications, including general lighting This has been possible in large part due to the use of current spreading layers (CSLs) in LEDs; these layers uniformly spread the current, thereby alleviating current crowding. We demonstrate the use of pristine graphene as CSLs and a graphene interlayer by inserting such a layer between the ITO and the p-GaN layer in GaN-based LEDs. First, LEDs with pristine graphene CSLs were unstable, leading to malfunction; this was confirmed to be originated from local damage by Joule heating due to the high sheet resistance and low work function of the pristine graphene. The improvement can be explained as resulting from the graphene interlayer, which has high transparency and conductivity and acts as a two dimensional potential barrier with an intentionally increased Schottky barrier height at the interface between the ITO and the p-GaN
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