Abstract
A much simplified method for transferring Gallium nitride (GaN) light emitting didoes (LEDs) to an unusual substrate, such as glass, Si, polyethylene terephthalate, or polyurethane, was demonstrated with spontaneously formed vertical tethers during chemical lift-off (CLO), without requiring a sacrificial layer or extra process steps. The LED arrays resided on a stamp that was coated with an adhesive layer. After the layer with the LEDs was transferred to the new substrates, the stamp was removed by acetone to complete the preparation. Over 3 × 3 cm2 LED arrays transferred to various substrates without any damage and misorientation. We also found that the optical and electrical characteristics improved after transfer due to decease in built-in stress. This simple and practical method is expected to greatly facilitate the development of transferrable full color GaN microLEDs on various substrates with either greatly reduced or no damage.
Highlights
Large-scale and flexible electronic and optoelectronic devices have recently attracted much attention for use in wearable displays, solar cells, sensors, and biomedical devices [1,2]
Separating Gallium nitride (GaN) light emitting didoes (LEDs) from a sapphire substrate by laser lift off (LLO) is an expensive process because it requires the use of a deep ultraviolet excimer laser [6,7,8]
We suggest a simplified transfer-printing method for GaN LEDs grown on a silicon wafer through spontaneously formed vertical tethers during the chemical lift off (CLO) process
Summary
Large-scale and flexible electronic and optoelectronic devices have recently attracted much attention for use in wearable displays, solar cells, sensors, and biomedical devices [1,2]. Gallium nitride (GaN)-based microscale light-emitting diodes (microLEDs) have attracted substantial attention in recent years as they have the potential to replace conventional organic light-emitting diodes (OLEDs) for flexible and bendable displays [3,4] Conventional routes to these devices involve epitaxial growth of active materials followed by chip fabrication, wafer dicing, and pick-and-place robotic manipulation into individually packaged components for interconnection by bulk wire-bonding. We suggest a simplified transfer-printing method for GaN LEDs grown on a silicon wafer through spontaneously formed vertical tethers during the CLO process This method does not require an additional sacrificial layer or extra process steps such as the fabrication of an anchor that would allow the development of mass transfer for flexible devices. GaN LEDs, before and after transfer, were studied by Raman, microphotoluminescence (microPL), and electroluminescence (EL) spectroscopy
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