One-step graphene coating of heteroepitaxial GaN films

Abstract

Today, state-of-the-art III-Ns technology has been focused on the growth of c-plane nitrides by metal-organic chemical vapor deposition (MOCVD) using a conventional two-step growth process. Here we show that the use of graphene as a coating layer allows the one-step growth of heteroepitaxial GaN films on sapphire in a MOCVD reactor, simplifying the GaN growth process. It is found that the graphene coating improves the wetting between GaN and sapphire, and, with as little as ~0.6 nm of graphene coating, the overgrown GaN layer on sapphire becomes continuous and flat. With increasing thickness of the graphene coating, the structural and optical properties of one-step grown GaN films gradually transition towards those of GaN films grown by a conventional two-step growth method. The InGaN/GaN multiple quantum well structure grown on a GaN/graphene/sapphire heterosystem shows a high internal quantum efficiency, allowing the use of one-step grown GaN films as 'pseudo-substrates' in optoelectronic devices. The introduction of graphene as a coating layer provides an atomic playground for metal adatoms and simplifies the III-Ns growth process, making it potentially very useful as a means to grow other heteroepitaxial films on arbitrary substrates with lattice and thermal mismatch.

Monolithic graphene oxide sheets with controllable composition

“…The spectra for all of the samples exhibit three primary features: a D band at B1,348 cm À 1 , a G band at B1,592 cm À 1 and a 2D band at B2,687 cm À 1 , which are all typical peak positions for graphene 14,[16][17][18][19][20][21] . However, the Raman spectra of the samples consistently show an intense D band (I D /I G Z1.0) related to domain boundaries, impurities and growth-nucleation sites [22][23][24][25] . Based on the Tuinstra-Koenig relationship 26 , the average distance between the defects in our samples was estimated to be less than B19 nm.…”

Stress relaxation of GaN microstructures on a graphene‐buffered Al2O3 substrate

“…Gallium nitride (GaN) is a promising semiconductor material for high‐efficiency, long‐lifetime optoelectronic devices, including light‐emitting diodes (LEDs), laser diodes, and photodetectors. Recently, the application of graphene layers to transparent and flexible conducting layers in GaN‐based LEDs has been successfully demonstrated 3–6. The graphene layers provide multiple functions such as high transmittance and good conductivity, with the spreading of heat occurring at a local area.…”

Van der Waals Epitaxy of III‐Nitride Semiconductors Based on 2D Materials for Flexible Applications

“…Over the past decade, graphene has been studied in depth as one of the most promising materials for the future. Various fabrication methods have been explored for graphene synthesis, such as mechanical cleaving (exfoliation), thermal decomposition, chemical exfoliation, chemical synthesis, chemical vapor deposition (CVD), microwave plasma synthesis, diffusion‐assisted synthesis (DAS), and arcdischarge synthesis . The key to vdWE is the preparation of large‐scale single‐crystalline graphene.…”

“…In the thermal decomposition method, graphene buffer layer is produced by subliming the surface of a SiC wafer under ultrahigh vacuum (UHV), which can be directly used as a substrate for the subsequent vdWE process. Furthermore, graphene films can be directly synthesized onto desired substrates without transfer printing by a DAS or atmospheric‐pressure chemical vapor deposition (APCVD) process, and such graphene‐coated substrates can be directly used in III‐nitride vdWE. In this section, we will discuss the above three approaches.…”

“…Inset in (e) shows the AFM surface morphology of GaN film grown on graphene coating layer. Reproduced with permission . Copyright 2012, IOP Publishing Ltd.…”