Mechanisms and Performance Analysis of GaN-Based Micro-LED Grown on Pattern Sapphire Substrate by Laser Lift-Off Process

Abstract

The laser lift-off (LLO) process was employed to fabricate a monochromatic GaN-based green micro-light-emitting-diode (Micro-LED) 14*14 arrays grown on pattern sapphire substrate (PSS) in this research. A new experimental phenomenon and internal mechanism of some epitaxial residues on the top and sidewalls of PSS protrusion after laser stripping were deeply discussed. In addition, the reasons for the formation of micro lattice dislocation of epitaxial layer crystal caused by laser were also analyzed. The leakage current of the chip array devices after LLO was more than 200 times higher than the device before LLO at the same voltage, but the light output current efficiency was discovered to be 109.7% higher under the 500 cd / m2 brightness. The results indicate peak wavelength was blue shift 3 nm once the LLO process had been performed. Furthermore, the optical pattern of green LED array from a "heart-shaped" distribution before LLO was changed into the maximum intensity directly above the array devices. The luminous angle was also reduced from ±75° to ± 65°, which indicates that the collimation of the light after LLO process was increased.The results are of high importance for understanding the optical properties of Micro-LED array devices after LL.

Progress in Color Conversion Technology for Micro‐LED

“…In the mid-20th century, different research groups have successfully fabricated various III-nitride microstructures, including microdisks, rings, pyramids, prisms, waveguides, and optically pumped vertical cavity surface emitting lasers. [67][68][69][70][71][72][73] In particular, the development of GaN-based arrays has applications in projectors, [74] visible light communications, [75][76][77][78] and medicine, [79][80][81] further promoting the development of III-group nitride microstructures. These new alloy nitride semiconductor materials have an energy band gap ranging from 1.9 to 6.2 eV, covering almost the entire visible light range and deep UV wavelengths.…”

Laser‐Based Micro/Nano‐Processing Techniques for Microscale LEDs and Full‐Color Displays

“…Not only is its in-plane dimension notably reduced, but also Micro-LED is much thinner in the vertical direction because the original growth substrate is commonly taken off. [47,69] It is believed substrate-free devices can remarkably improve the display contrast and suppress the sidewall emission induced by the thick substrate.…”

“…Reproduced with permission. [69] Copyright 2022, IOP Publishing. www.advmattechnol.de peak intensity and pulse width.…”

“…In the case of Micro-LED LLO (Figure 8c), the care that should be taken is that the laser beam size and pulsed laser intensity should be reduced in order to ensure a high lift-off success rate. [42,69] Suitable strategies for beam-shaping, beam-scanning, and beam profile control are also important factors for further improving the Micro-LED LLO performance. As an example, Coherent [115] developed a commercial UVblade LLO system for fast Micro-LED LLO.…”

“…In addition, the transfer speed can be further enhanced by using a multiple beam scanning strategy. Specifically, an array of laser beams was formed by using diffractive 266 nm DPSS laser >600 mJ cm −2 10 ns Glass Adhesive bonding using polyimide 4-inch [30] 266 nm DPSS laser 300 mJ cm −2 5 ns UV tape Adhesive bonding using UV tape 2-inch wafer [47] 266 nm DPSS laser <600 mJ cm −2 Glass Adhesive bonding using polyimide 12 mm × 10 mm [42] 266 nm DPSS laser Acrylate adhesive tape Adhesive bonding [132] 248 nm KrF >950 mJ cm −2 20 ns Glass PDMS glue bonding 14 × 14 array [69] www.advmattechnol.de optics, and projected onto the sample simultaneously, as schematically shown in Figure 11b. this leads to parallel transfers of multiple arrays at the same time.…”