Growth of GaN Micro- and Nanorods on Graphene-Covered Sapphire: Enabling Conductivity to Semiconductor Nanostructures on Insulating Substrates

Abstract

The self-catalyzed growth of vertically aligned and hexagonally shaped GaN micro- and nanorods on graphene transferred onto sapphire is achieved through metal organic vapor phase epitaxy. However, a great influence of the underlying substrate is evident, since vertically aligned structures with a regular shape could not be grown on graphene transferred to SiO2. The optical properties of the regular GaN nanorods were investigated by spatially and spectrally resolved cathodoluminescence showing defect related emission only near the interface between the sapphire substrate and nanorods but not from their upper part. Micro-raman spectroscopy confirms that the single-layer graphene remains virtually unchanged in terms of the Raman signal, even after undergoing high temperatures (similar to 1200 degrees C) during nanorod growth. Furthermore, Raman mapping demonstrates that GaN structures predominantly grow on defective parts of graphene, giving new insight into the nucleation and growth mechanism of semiconductors on graphene. To validate the conductivity of graphene, when being attached to the sapphire substrate and after the nanorod growth, current voltage investigations were carried out on single, as-grown, GaN nanorods with a nanoprober in a scanning electron microscope. These measurements demonstrate the viability of graphene as a conductive electrode, for example, as a back contact for GaN nanorods grown on insulating sapphire

Fabrication of gallium nitride and nitrogen doped single layer graphene hybrid heterostructures for high performance photodetectors

“…Therefore, carbon acts as a parasite degrading the material quality of GaN. www.nature.com/scientificreports/ Comparing with literature, M. Heilmann et al 25 attained the ratio of intensities between YL and NBE (I YL /I NBE ) value at around 2 for GaN micro-and nano-rods grown on SLG substrates, emphasizing the fact that YL dominates. Similarly, H. Yang et al 63 attained the value of I YL /I NBE as 5 for GaN grown on reduced graphene oxide (rGO) sheets.…”

“…Graphene, a two-dimensional (2D) material with a planar honeycomb like configuration of sp 2 hybridized carbon atoms, has attracted enormous interest for use in various optical and electronic device applications due to its unique material properties such as high optical transparency, thermal and electrical conductivity and mechanical properties 24 , 25 . Numerous techniques like mechanical cleavage from bulk graphite, CVD, reduction of graphene oxides (GO) from bulk graphite, deposition of ultra-thin graphite from SiC decomposition and liquid phase exfoliation, are being employed for the preparation of graphene 26 – 30 .…”

“…mechanical properties 24,25 . Numerous techniques like mechanical cleavage from bulk graphite, CVD, reduction of graphene oxides (GO) from bulk graphite, deposition of ultra-thin graphite from SiC decomposition and liquid phase exfoliation, are being employed for the preparation of graphene [26][27][28][29][30] .…”

Graphene‐Assisted Epitaxy of Nitrogen Lattice Polarity GaN Films on Non‐Polar Sapphire Substrates for Green Light Emitting Diodes

“…[ 12–14 ] Till now, most efforts of III‐nitrides epitaxy are based on metal organic vapor phase epitaxy (MOVPE), where an AlN nucleation/buffer layer is necessary to guarantee the successful epitaxy of GaN. [ 15–18 ] Oxygen‐plasma pretreatment on the graphene is often used as a way to generate more nucleation sites for AlN. [ 19–22 ] In addition, GaN grown by MOVPE with oxygen‐plasma pretreatment are all Ga‐lattice‐polarity while N‐lattice‐polarity has never been reported until now to the best of our knowledge.…”

Polarized Raman and photoluminescence studies of a sub-micron sized hexagonal AlGaN crystallite for structural and optical properties

“…The III‐nitride microdisk structures are already used for demonstrating room‐temperature continuous wave lasing via high‐Q whispering gallery modes, which are applicable for laser diodes . The presence of whispering gallery modes in the microrods is a signature of excellent morphological, structural, and high optical quality of the material . Moreover, these microstructures have recently attracted for aforementioned applications because of their special properties such as variable‐color light emission, high‐density integration, material and crystalline quality .…”