Self-Assembled UV Photodetector Made by Direct Epitaxial GaN Growth on Graphene

Hybrid systems based on the combination of crystalline bulk semiconductors with 2D crystals are identified as promising heterogeneous structures for new optoelectronic applications. The direct integration of III-V semiconductors on 2D materials is very attractive to make practical devices but the preservation of the intrinsic properties of the underlying 2D materials remains a challenge. In this work, we study the direct epitaxy of self-organized GaN crystals on graphene. We demonstrate that severe metal-organic chemical vapor deposition growth conditions of GaN (chemically aggressive precursors and high temperatures) are not detrimental to the structural quality and the charge carrier mobility of the graphene base plane. Graphene can therefore be used both as an efficient sensitive material and as a substrate for GaN epitaxy to make a self-assembled UV photodetector. A responsivity as high as 2 A W^-1 is measured in the UV-A range without any further postprocessing compared to simple deposition of contact electrodes. Our study opens the way to build new self-assembled 2D/III-V hybrid optoelectronic devices by direct epitaxy.