Electroluminescence in a rectifying graphene/InGaN junction

Abstract

A graphene-InGaN Schottky junction has been successfully fabricated by transferring graphene layers onto n-type In_0.23Ga_0.77N/GaN/Al₂O₃ substrates. Current–voltage (I–V) measurement across the junction demonstrates the rectifying behaviour. Temperature dependent I–V characteristics in a range of 10 K to 300 K reveal that the charge transport mechanism is dominated by thermionic emission. Also, it is observed that the charge-transfer induced variation of Fermi energy of graphene affects the flow of current. This graphene/InGaN junction shows electroluminescence (EL) characteristics under a forward bias, producing bright blue emission (430 nm) at room temperature. As the temperature increases, the EL peak is shifted to a lower energy with a reduced peak intensity due to the increased nonradiative recombination rate. The dependence of EL intensity on the current of the graphene/InGaN junction confirms the band-to-band recombination mechanism in the InGaN layer by the bimolecular radiative recombination. Therefore, the observed results provide an insight for implementing graphene based Schottky-junction devices with tunable emission by utilizing the variable bandgap of the InGaN layer.