| 초록 |
A self-contained and individually-addressable light emitting crystal possesses a unique opportunity to realize ultra-small and ultra-high resolution pixel for next-generation display. Especially, GaN/InGaN-based LEDs possess advantages over OLEDs for high-efficiency and long-term stability. However, implement of red-green-blue (RGB) colors on a single chip substrate as well as emission quenching through surface nonradiative recombination sites remain a challenge for GaN/InGaN-based micro-LEDs. Here, we explore electrically-driven light emission behavior from vertically standing InGaN/GaN micro-crystals (µ-crystals) with well-defined crystal facets and tunable size. InGaN/GaN µ-crystals have hollow pedestals that are weakly bound to the substrate surface, thus enabling individual manipulation and/or collective transfer to another target surface. The light-emitting diodes (LEDs) with individual InGaN/GaN µ-crystals exhibit strong electroluminescence (EL) with unique features such as variation of emission spectra with respect to crystal diameter and driving voltage bias. Comparative optical & simulation analyses indicate the strong correlation between EL wavelengths and the dominant emitting regions of the InGaN/GaN crystal planes. This is further supported by scanning transmission electron microscopic investigation of quantum well structures that have strong dependence on size and crystal facets. This achievement represents additional opportunities to impose new functions and applications in LEDs, such as full-color flexible display, optogenetics and so on. |
