| 초록 |
Micro-LEDs (µ-LEDs) based on inorganic-semiconductors are thus considered to overcome such limits of existing display technologies. Driven by the advances in GaN-based technology, extreme-brightness and long-term operation can be readily achieved with existing GaN/InGaN multiple quantum well (QW) LEDs. 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 have explored bottom-up based epitaxial growth of InGaN/GaN crystals with precisely-controlled position and variable size on same substrate. To achieve our target structure, we established a low-temperature solution-phase synthesis of 3D architectures constructed with well-regulated, single crystalline ZnO crystals, and subsequent heteroepitaxial MOCVD growth of GaN/InGaN multi quantum wells with following strategies. 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. |
