Hybrid Full-Color Inorganic Light-Emitting Diodes Integrated on a Single Wafer Using Selective Area Growth and Adhesive Bonding

Abstract

In recent years, research into implementing microdisplays for use in virtual reality and augmented reality has been actively conducted worldwide. Specifically, inorganic light-emitting diodes (LED) have many advantages in microdisplays, so much effort has been made to implement them in various ways. However, it is still challenging to realize a display with high resolution using only inorganic LEDs without color conversion layers because a typical LED chip is designed to emit only one color on a single wafer. In this study, we integrated high-efficiency red, green, and blue (RGB) LED material systems on the same sapphire substrate. Since the blue and green LED structures comprised the same GaN semiconductor, a metalorganic chemical vapor deposition method was used to integrate them. Meanwhile, the red LEDs made from another semiconductor were incorporated into the blue/green LEDs using a wafer-bonding technique. The fabricated hybrid RGB LEDs were able to cover a wide color space. In addition, the RGB LED material systems consisting of a high-quality single crystal were stably combined on the sapphire substrate without any structural defects. We show the possibility of their use in displays by integrating the RGB LEDs on one chip and suggest that their utilization could range from large-area LED displays to ultrahigh-resolution small displays.

Micro Light‐Emitting Diodes for Display and Flexible Biomedical Applications

“…A number of researches in the industry and at universities have developed the chip‐based µLED displays and biomedical devices . Although the assembly process for LED digital signage is well established based on the conventional LED technologies, chip‐based µLED display has a critical limitation in the mass production of low‐cost consumer TVs caused by handling millions of individual chip transfer . Since chip‐based µLED displays are already a mature technology for outdoor LED screens, this review will not discuss this in detail.…”

High-Performance Color-Converted Full-Color Micro-LED Arrays

“…Another approach to avoid the mass-transfer process is the fabrication of full-color micro LEDs based on blue or UV micro LEDs and color-conversion materials of blues, greens, and reds. For color-conversion materials, nanophosphors and quantum dots (QDs) can be used [8][9][10][11]. For example, Han et al [9] deposited RGB QDs on top of a UV LED array using the aerosol jet printing method to form individual subpixels.…”

Tripling the Optical Efficiency of Color-Converted Micro-LED Displays with Funnel-Tube Array

“…Moreover, the light emission efficiency and degradation rate of RGB micro-LEDs are different; as a result, it may need complicated driving circuit to maintain the color rendering index during operation. The second method is monolithic integration of RGB micro-LEDs via adhesive bonding [6]. However, the fabrication process is complicated, because the substrates for growing blue/green micro-LEDs and red micro-LED are different.…”