Vertical light-emitting diodes with surface gratings and rough surfaces for effective light extraction

Area of Science:

• Optoelectronics
• Materials Science

Background:

• Light extraction efficiency is crucial for optimizing light-emitting diode (LED) performance.
• Surface texturing is a common method to improve light extraction in LEDs.

Purpose of the Study:

• To investigate the optimal grating period for surface grating fabrication on vertical light-emitting diodes (VLEDs).
• To compare the light extraction efficiency of VLEDs with surface gratings versus those with rough surfaces.

Main Methods:

• Fabrication of surface gratings on VLEDs using a combination of photoelectrochemical (PEC) etching and phase mask interferometry.
• Construction of a Lloyd's interferometer within a PEC electrolyte (KOH) to create gratings with various periods.
• Fabrication of VLEDs with rough surfaces using two different KOH wet etching methods for comparison.

Main Results:

• Smaller grating periods (<2 μm) resulted in more effective light extraction for grating VLEDs.
• Grating VLEDs with short periods exhibited higher light extraction efficiencies than VLEDs with rough surfaces.
• The improved light extraction of gratings was observed even when their groove depth was less than the root-mean-square roughness of the textured surfaces.

Conclusions:

• Surface grating fabrication via PEC etching and phase mask interferometry is an effective method for enhancing VLED light extraction.
• Optimizing grating period is critical, with shorter periods (<2 μm) demonstrating superior performance.
• Surface gratings offer a more efficient light extraction enhancement strategy compared to randomly rough surfaces for VLEDs.