Graphene as a substrate and bottom electrode for high density and vertically aligned GaN nanocolumns

We report the preliminary result of graphene being simultaneously utilized as a substrate and bottom electrode for the growth of GaN nanocolumns. The graphene was transferred to silica glass as the carrier substrate. AlN buffer layer as a nucleation site enables a high density of GaN nanocolumns on graphene while maintaining the growth along c-axis orientation. Furthermore, AlN is able to minimize damage on graphene caused by impinging active N species generated by radio frequency N plasma source, as it was measured by Raman spectroscopy. The growth direction and verticality of our GaN nanocolumns was further analyzed using high resolution X-ray diffraction technique. Optical characterization measurement shows near band edge emission from wurtzite GaN with no yellow luminescence emission. To investigate the potential of graphene as a bottom electrode, Schottky contact was successfully made using as-grown ensemble GaN nanocolumns doped with Si atoms as the top contact. There was no transfer process being done prior to current-voltage measurement. The results of this initial work pave a way towards realizing low cost and high performance ultraviolet light emitting diodes based on III-N semiconductors and graphene.