Transfer Printing of Roughened GaN‐Based Light‐Emitting Diodes into Reflective Trenches for Visible Light Communication

Abstract

There is a great need to integrate dissimilar visible light components for the fabrication of thin, flexible, and 3D structures in the next generations of display and communication systems. Compared with monolithic integration, microtransfer printing (μTP) of miniaturized devices allows the heterogeneous assembly of diverse devices in a scalable and cost‐effective manner for expanded functionality. Here, advantages of μTP technology to boost the directional light output of light‐emitting diodes (LEDs) are demonstrated with a remarkable sevenfold enhancement compared with devices on the original substrate. This is achieved using an original integrated approach to roughen the backside of the GaN‐on‐Si LEDs during their release together with their printing into 10 μm‐deep reflective trenches formed in a new substrate. To address the bending of the 110 × 110 μm2 LEDs due to the internal stress from the GaN layers, compensational stress with deposited SiNx is engineered, which results in flat surfaces and successful transfer printing. Finally, the LEDs in trench are used in visible light communication (VLC), showing higher signal‐to‐noise ratio and lower bit‐error rate compared with a flat platform due to higher power collected. This strategy could be used to integrate different colors of LEDs for enhanced VLC as well as in displays.

Keywords

• GaN light-emitting diodes
• light extraction
• microtransfer printing
• roughening
• visible light communication