Monolithic integration of AlGaInP-based red and InGaN-based green LEDs via adhesive bonding for multicolor emission

Jae-Phil Shim,Seok-Jin Kang,Sanghyeon Kim,Dong-Seon Lee,Seung-Hyun Mun,Soo-Young Choi,Jung-Hong Min,Chang-Mo Kang

doi:10.1038/s41598-017-11239-4

Abstract

In general, to realize full color, inorganic light-emitting diodes (LEDs) are diced from respective red-green-blue (RGB) wafers consisting of inorganic crystalline semiconductors. Although this conventional method can realize full color, it is limited when applied to microdisplays requiring high resolution. Designing a structure emitting various colors by integrating both AlGaInP-based and InGaN-based LEDs onto one substrate could be a solution to achieve full color with high resolution. Herein, we introduce adhesive bonding and a chemical wet etching process to monolithically integrate two materials with different bandgap energies for green and red light emission. We successfully transferred AlGaInP-based red LED film onto InGaN-based green LEDs without any cracks or void areas and then separated the green and red subpixel LEDs in a lateral direction; the dual color LEDs integrated by the bonding technique were tunable from the green to red color regions (530–630 nm) as intended. In addition, we studied vertically stacked subpixel LEDs by deeply analyzing their light absorption and the interaction between the top and bottom pixels to achieve ultra-high resolution.

Highlights

The color of the light emitted from an inorganic light-emitting diodes (LEDs) is determined by the bandgap energy of the material in the active region
The InGaN-based green LED epitaxial structure grown on a double-sided polished sapphire (DSPS) substrate and the AlGaInP-based red LED epitaxial structure grown on a GaAs substrate were used for green (~530 nm) and red (~630 nm) light emission, respectively
The key point is that we transferred the red LED epitaxial layer onto the green LEDs using bonding and chemical wet etching and made the red LED subpixels

Summary

Introduction

The color of the light emitted from an inorganic LED is determined by the bandgap energy of the material in the active region. The scaling issues have been overcome by introducing either stamps, or electrostatic or electromagnetic methods, transfer yield problems such as missing pixels on a display panel during the LED transfer process still remain These approaches sometimes require the high-cost laser lift-off (LLO) process to remove the substrate of epitaxial layer[16, 20, 21]. One route could be achieved through interface designs such as ZnO/GaN or growth techniques of hetero junctions like n-p-n structures, the lighting efficiency needs to be improved[22, 23] Another group suggested stacking wafer-level thin films of the III-V-based LEDs to realize multicolor pixels[24]. We were able to realize the laterally arranged subpixel (LAS)-type structure and the vertically stacked subpixel (VSS)-type array structure which increases the display resolution by up to three times more than the LAS-type[24, 25]

Methods

Results

Conclusion