III-N LEDs with graphene double-sided InGaN/GaN multiple quantum well structures

Abstract

For a decade, graphene has been mainly used for III-nitrides based light emitting diodes (LEDs) as a transparent and current spreading layer by chemical vapor deposition (CVD) growth method. Herein, we report new stack design, graphene double-sided InGaN/GaN multiple quantum well structures, which can be applied as both a buffer layer and a transparent conducting electrode. The InGaN/GaN MQW structures on graphene buffered GaN template show enhancement of indium phase separation with a rougher GaN surface than conventional MQW systems on two-step growth GaN films. The MQW structures on one-step GaN using graphene coating layer display high internal quantum efficiency (IQE) value and negligible emission wavelength peak shift along current density change, which is similar characterization of polarization free quantum dots (QDs). Furthermore, a CVD monolayer graphene transferred onto the top of the p-GaN/MQWs/n-GaN/u-GaN/graphene/sapphire heterosystem, which has high transmittance in ultraviolet regions than indium tin oxide (ITO) layer and lower forward voltage than MQW structures with sole graphene buffer layer. This unique stacking method diversifies graphene applications for future optoelectronic devices based on III-Ns compound semiconductor.