Use of graphene for forming Al-based p-type reflectors for near ultraviolet InGaN/AlGaN-based light-emitting diode

Abstract

We demonstrated the improved performance of near UV (365 nm) InGaN/AlGaN-based LEDs using highly reflective Al-based p-type reflectors with graphene sheets as a diffusion barrier. The use of graphene sheets did not degrade the reflectance of ITO/Al contacts, viz. similar to 81% at 365 nm. The ITO/graphene/Al contacts annealed at 300 degrees C exhibited better ohmic behavior with a specific contact resistance of 1.5 x 10(-3) Omega cm(2) than the ITO/Al contact (with 9.5 x 10(-3) Omega cm(2)). Near UV LEDs fabricated with the ITO/graphene/Al contact annealed at 300 degrees C showed a 7.2% higher light output (at 0.1 W) than LEDs with the ITO/Al reflector annealed at 300 degrees C. The SIMS results exhibited that, unlike the ITO/graphene/Al, the ITO/Al contacts undergo a significant indiffusion of Al atoms toward the GaN after annealing. Furthermore, both Ga and Mg atoms were also more extensively outdiffused in the ITO/Al contacts after annealing. On the basis of the SIMS and electrical results, the possible explanations for the annealing-induced degradation of the ITO/Al contacts are described and discussed. (C) 2014 Elsevier B.V. All rights reserved.