Morphologies and optical and electrical properties of InGaN/GaN micro-square array light-emitting diode chips

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) based light-emitting diodes (LEDs) are crucial for modern lighting and display technologies.
• Fabrication of three-dimensional (3D) LED structures presents challenges in controlling morphology and maintaining optimal optical and electrical properties.
• Focused Ion Beam (FIB) etching offers precise control over 3D structures but can impact device performance.

Purpose of the Study:

• To investigate the impact of Focused Ion Beam (FIB) etching parameters, specifically beam current and etch depth, on the properties of InGaN/GaN micro-square array LEDs.
• To understand the degradation mechanisms associated with FIB etching and explore post-etching treatments for performance enhancement.
• To reveal the relationship between micro-square array depth and light extraction efficiency in 3D-LEDs.

Main Methods:

• Fabrication of InGaN/GaN micro-square array LEDs using FIB etching.
• Systematic variation of FIB beam current and micro-square array depth.
• Characterization of surface morphology, optical properties (cathodoluminescence), and electrical properties (current-voltage characteristics).
• Post-etching treatment using potassium hydroxide (KOH).
• 3D finite difference time domain (FDTD) simulations to analyze light extraction mechanisms.

Main Results:

• Increased FIB beam current leads to degradation of sidewall surface morphology, optical properties, and electrical characteristics of the micro-chips.
• Post-etching with KOH improves current-voltage and luminescence performance, with optimal results achieved after specific etching times.
• Light extraction efficiency decreases as the FIB etch depth of the micro-square array increases.
• FIB etching parameters significantly influence the performance and light extraction of 3D-LED devices.

Conclusions:

• FIB etching parameters must be carefully controlled to avoid performance degradation in InGaN/GaN micro-LEDs.
• Post-etching treatments, such as KOH etching, can mitigate some of the negative effects of FIB processing.
• Micro-square array depth is a critical factor affecting light extraction efficiency in 3D-LEDs, necessitating optimization for improved device performance.