Selective-Area Growth Mechanism of GaN Microrods on a Plateau Patterned Substrate.

Area of Science:

• Materials Science
• Semiconductor Growth
• Nanotechnology

Background:

• Selective-area growth (SAG) is crucial for fabricating complex semiconductor devices.
• Understanding the surface properties influencing GaN growth on patterned substrates is essential for advanced applications.

Purpose of the Study:

• To investigate the underlying mechanism of gallium nitride (GaN) selective-area growth (SAG) on polished plateau-patterned sapphire substrates (PP-PSS).
• To identify the key material properties responsible for the observed growth selectivity.

Main Methods:

• Experimental deposition of aluminum nitride (AlN) buffer layers and GaN on PP-PSS.
• Analysis of AlN buffer layers using indirect samples on bare c-plane substrates.
• Direct characterization of PP-PSS using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD).

Main Results:

• GaN SAG was exclusively observed on the plateau regions of the PP-PSS, regardless of growth cycles.
• AlN buffer layers on plateau regions showed higher surface energy and a specific crystal orientation (AlN [001]).
• Non-plateau regions lacked crystallinity and exhibited lower surface energies, confirmed by TEM and EBSD analyses.

Conclusions:

• GaN SAG on PP-PSS is critically dependent on the crystallinity, crystal orientation, and surface energy of the underlying AlN buffer layer.
• The distinct properties of the AlN layer on plateau regions dictate the site-specific growth of GaN under identical deposition conditions.