Vertical GaN nanocolumns grown on graphene intermediated with a thin AlN buffer layer

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Gallium nitride (GaN) is a crucial semiconductor for electronic and optoelectronic devices.
• Growing GaN on low-cost, flexible substrates like graphene is highly desirable but challenging.
• Existing methods often suffer from defects, stress, or damage to the graphene substrate.

Purpose of the Study:

• To develop a method for self-assembled growth of high-density, vertically-oriented n-doped GaN nanocolumns on graphene.
• To investigate the role of an aluminum nitride (AlN) buffer layer in enabling this growth.
• To assess the quality, stress, and optoelectronic properties of the resulting GaN nanostructures.

Main Methods:

• Radio-frequency plasma-assisted molecular beam epitaxy (RF-PAMBE) for GaN nanocolumn growth.
• Transfer of graphene onto silica glass substrates.
• Use of a migration-enhanced epitaxy (MEE) grown AlN buffer layer for nucleation.
• Characterization using micro-Raman spectroscopy, micro-photoluminescence (µ-PL), and transmission electron microscopy (TEM).

Main Results:

• Achieved high-density, vertically-oriented, c-axis aligned n-doped GaN nanocolumns on graphene.
• The AlN buffer layer effectively protected graphene from plasma damage and enabled defect-free wurtzite GaN growth.
• The grown GaN nanocolumns were virtually stress-free, exhibiting strong near band-edge emission and no yellow luminescence.

Conclusions:

• RF-PAMBE with an MEE-grown AlN buffer is a viable method for growing high-quality GaN nanocolumns on graphene.
• This approach minimizes substrate damage and results in stress-free, high-performance GaN nanostructures.
• The findings open possibilities for low-cost, high-performance III-N electronic and optoelectronic devices on graphene.