Micro/Nano LEDs

Individually controllable μ-LED arrays have recently been implemented to achieve a high-resolution adaptive driving beam (ADB) or advanced forward lighting system (AFS) for headlights of vehicles, which have 64 μ-LED pixels per 1 mm2, a pixel area of 115 μm x 115 μm, and pixel pitch of 125 μm in both directions. In order to realize high-brightness InGaN based individually addressable μ-LED arrays for the high-resolution ADB/AFS application, the luminous flux as well as thermal dissipation of the μ-LED arrays should be further improved

A pixel array of GaN-based μ-LEDs based on a flip-chip structure and driven by a passive matrix/active matrix was fabricated. The light output power of 16x16(PM) or 32x32(AM) pixelated μ-LEDs for headlights of vehicles was greatly improved by enhancing the reflectivity and coverage of the p-electrode (PM) and the formation of ZnO nanorods on sapphire substrates(AM).

The energy transfer (ET) between InGaN/GaN multiple-quantum-well (MQW) nanorods (NRs) and semiconductor nanocrystals (NCs) for efficient color conversion is studied. An exceptional contribution of carrier transport confinement to the ET mechanisms is observed in the proximal side-wall coupling system, which consists of InGaN/GaN NRs and CdSe NCs.

We fabricate nonpolar InGaN/GaN single quantum-well based a-plane nanopillar green LED. The top-down fabrication method was used for fabricating nanopillar LED, where self-aligned In3Sn nanodots were used as an etching mask. In order to achieve uniform current injection into nanopillars, a p-type transparent ITO contact having a slanted oblique-angle layer is selectively deposited on the top of each nanopillar.

High-power dimmable blue GaN-based LED light sources with a small form factor is essential for realization of various novel applications, such as underwater visible light communication (VLC), adaptive headlights for vehicles, and photodynamic therapy. The realization of the light sources with a small form factor can be achieved by integrating high-power GaN-based LEDs with AlGaN/GaN-based heterojunction field-effect transistors (HFETs).

The hybrid integration of GaN-based vertical injection LEDs (VI-LEDs) with AlGaN/GaN-based HFETs having multi-level metallization via the flip-chip bonding technique is examined. Furthermore, dimmable micro-LED arrays on AlGaN/GaN-based power HFETs is realized.