Core-shell GaN/AlGaN nanowires grown by selective area epitaxy

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Gallium nitride (GaN) and aluminum gallium nitride (AlGaN) are crucial materials for optoelectronic devices.
• Core-shell nanowire structures offer unique advantages for device performance.
• Nonpolar m-plane growth is challenging but essential for high-efficiency devices.

Purpose of the Study:

• To investigate the growth of GaN/AlGaN core-shell nanowires using selective area metal organic chemical vapor deposition.
• To analyze the effect of carrier gas composition on AlGaN shell morphology and optical properties.
• To explore the potential for ultraviolet light-emitting diodes (LEDs) and micro-LEDs.

Main Methods:

• Selective area metal organic chemical vapor deposition (MOCVD) for GaN/AlGaN core-shell nanowires.
• Controlled growth using pure N2 versus mixed N2/H2 carrier gases.
• Characterization of surface morphology, Al composition, optical properties, and defect analysis.

Main Results:

• Pure N2 carrier gas resulted in smooth nonpolar m-plane AlGaN shells with superior optical properties.
• Mixed N2/H2 carrier gas led to striated surfaces, a common issue in nonpolar III-nitride growth.
• Al incorporation efficiency decreased with increasing Al molar flow due to geometric, strain, and parasitic effects.
• Defect-related luminescence, attributed to (V_III-2O_N)^1- complexes, was observed for Al content ≥ 30%.
• Partial dislocations were identified as dominant defects in AlGaN shells.

Conclusions:

• The growth scheme demonstrates viability for large-area efficient ultraviolet LEDs.
• Nonpolar m-plane AlGaN/GaN quantum wells on GaN nanowires show excellent morphology and optical emission.
• This approach is promising for next-generation ultraviolet micro-LEDs.