Strategically constructed patterned sapphire with silica array to boost substrate performance in GaN-based flip-chip...

Area of Science:

• Materials Science
• Optoelectronics
• Solid State Physics

Background:

• Gallium nitride (GaN)-based light-emitting diodes (LEDs) are crucial for efficient lighting.
• Patterned sapphire substrates (PSS) are used to improve GaN epitaxy and device performance.
• Enhancing light extraction and reducing defects in GaN LEDs remains a key challenge.

Purpose of the Study:

• To develop and evaluate a novel patterned sapphire with silica array (PSSA) substrate.
• To investigate the impact of PSSA on GaN epitaxy and the performance of flip-chip LEDs.
• To assess the potential of PSSA as an improved substrate for III-nitride optoelectronic devices.

Main Methods:

• Fabrication of PSSA using strategic substrate construction.
• Growth of GaN epilayers on PSSA and conventional PSS.
• Characterization using X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM).
• Performance evaluation of flip-chip LEDs, including light output power and far-field radiation patterns.

Main Results:

• The PSSA substrate significantly improved the light output power of flip-chip LEDs by 16.5% compared to PSS.
• GaN epilayers grown on PSSA exhibited superior crystalline quality due to reduced misfit at the coalescence boundary.
• Enhanced light extraction efficiency was observed for LEDs on PSSA, attributed to the low refractive-index contrast between silica and air.
• A more convergent emission pattern was achieved with the PSSA substrate.

Conclusions:

• PSSA serves as an effective substrate for defect suppression in GaN epitaxy.
• The PSSA substrate enhances light extraction efficiency in GaN-based LEDs.
• PSSA presents a promising new substrate platform for advanced III-nitride optoelectronic devices.