A GaN bulk crystal with improved structural quality grown by the ammonothermal method

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Technology

Background:

• High-performance optoelectronic devices require high-quality substrates, with non-polar or semipolar gallium nitride (GaN) showing promise over conventional c-plane.
• Bulk GaN growth allows for substrates with various crystal orientations, crucial for device optimization.

Purpose of the Study:

• To report improvements in the structural quality of GaN grown via the ammonothermal method.
• To assess the commercial viability of ammonothermal GaN growth for substrate applications.

Main Methods:

• Ammonothermal growth of bulk GaN.
• Plan-view transmission electron microscopy (PVTEM) for structural quality assessment.
• Estimation of threading dislocation densities on Ga and N faces.

Main Results:

• Threading dislocation densities were found to be below 1 x 10^6 cm^-2 (Ga face) and 1 x 10^7 cm^-2 (N face).
• No dislocation generation was observed at the interface on the Ga face, with minimal defects on the N face.
• Structural quality improvements were achieved, complementing previous findings on growth rate and scalability.

Conclusions:

• The ammonothermal method yields high-quality GaN suitable for advanced optoelectronic substrates.
• The demonstrated structural quality, combined with growth rate and scalability, supports the commercial feasibility of this GaN growth technique.