- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Improved Color Purity of Monolithic Full Color Micro-LEDs Using Distributed Bragg Reflector and Blue Light Absorption Material
摘要： In this study, CdSe/ZnS core-shell quantum dots (QDs) with various dimensions were used as the color conversion materials. QDs with dimensions of 3 nm and 5 nm were excited by gallium nitride (GaN)-based blue micro-light-emitting diodes (micro-LEDs) with a size of 30 μm × 30 μm to respectively form the green and red lights. The hybrid Bragg re?ector (HBR) with high re?ectivity at the regions of the blue, green, and red lights was fabricated on the bottom side of the micro-LEDs to re?ect the downward light. This could enhance the intensity of the green and red lights for the green and red QDs/micro-LEDs to 11% and 10%. The distributed Bragg re?ector (DBR) was fabricated on the QDs color conversion layers to re?ect the non-absorbed blue light that was not absorbed by the QDs, which could increase the probability of the QDs excited by the re?ected blue light. The blue light absorption material was deposited on the DBR to absorb the blue light that escaped from the DBR, which could enhance the color purity of the resulting green and red QDs/micro-LEDs to 90.9% and 90.3%, respectively.
关键词： micro-light-emitting diodes,color conversion layer,distributed Bragg re?ector,quantum dots,hybrid Bragg re?ector,blue light absorption material
更新于2025-09-23 15:21:01
-
Impact of grain growth of silver reflective electrode by electron bombardment on external quantum efficiency of III-nitride micro-light-emitting diode arrays
摘要： The effect of electron-beam irradiation (EBI) on Ag reflector is investigated in order to improve the efficiency of flip-chip InGaN/GaN multiple-quantum-wells micro light-emitting diode (μ-LED) arrays. After EBI, small size grains are diffused and then become larger grain. Therefore, grain boundaries are reduced which originates the crystal quality and reflectance of Ag reflect to improve. Grain size of Ag reflector is increased with the increase in EBI time that is consistently observed by different kinds of material characterizations. 5 minutes EBI-based Ag reflector shows higher reflectance (~91 %) at 450 nm than without EBI sample (~84 %). Finally, without and with EBI on Ag reflector-based μ-LED arrays are fabricated. After EBI, there is no change in forward bias voltage except optical performances. At driving current, Ag reflector with EBI-based μ-LEDs has higher light-output-power, electroluminescence intensity and electroluminescence distribution over the chip area compared to without EBI-based μ-LEDs. Usually, increased light-extraction-efficiency causes the external-quantum-efficiency of the μ-LEDs to increase. These enhanced optoelectronic performances are consistently described by using microscopic and macroscopic characterizations.
关键词： Ag reflector,Electron-beam irradiation,reflectance,micro light-emitting diodes,grain size
更新于2025-09-19 17:13:59
-
Effects of interfaces and current spreading on the thermal transport of micro-LEDs for kA-per-square-cm current injection levels
摘要： The three-dimensional thermal characteristics of micro-light-emitting diodes (mLEDs) on GaN and sapphire substrates were studied with forward-voltage methods, thermal transient measurements, and infrared imaging. The mLEDs on the GaN substrate showed an approximately 10 °C lower junction temperature and smaller amplitude of the K factors than those on the sapphire substrate under the current injection level of 4 kA cm?2. The thermal transient measurement showed that the spreading thermal resistances of the mesa, the GaN epilayer, and the interface of the GaN/substrate were reduced significantly for mLEDs on the GaN substrate because of the high-quality GaN crystal and the interfaces. The infrared thermal images showed lower total average junction temperatures and more uniform temperature distributions for the mLEDs on the GaN substrate, which were also simulated with APSYS software. The thermal transport mechanisms are discussed for the lateral and vertical directions in the mLEDs.
关键词： sapphire substrate,micro-light-emitting diodes,GaN substrate,junction temperature,thermal transport,infrared imaging,APSYS simulation
更新于2025-09-11 14:15:04
-
Wirelessly Operated, Implantable Optoelectronic Probes for Optogenetics in Freely Moving Animals
摘要： Recording and interrogating brain activities using optical methods have become emerging technologies in neuroscience. Traditional tools for optogenetic stimulation in the deep brain are mostly based on implantable fibers, imposing constraints on the animal movement. Recently developed microscale light-emitting diodes (micro-LEDs), which can be wirelessly operated, serve as injectable light sources that directly interact with neural systems. Here, we exploit a wirelessly controlled, implantable system for optogenetic studies in behaving animals. Thin-film indium gallium nitride (InGaN)-based blue micro-LEDs transferred onto flexible probes are injected into the animal brain and optically activate channelrhodopsin-2 expressing neurons. A customized circuit module with a battery is employed to modulate the micro-LED, which is remotely controlled at a distance up to 50 m via 2.4-GHz radio frequency communications. The systems are implemented on freely moving mice, and demonstrate optogenetic modulation of locomotive behaviors in vivo. Moreover, independent and synchronous control of multiple animals is accomplished with the communication unit in the design circuit. The proposed system provides the potential for advanced optical neural interfaces and offers solutions to study complicated animal behaviors in neuroscience research.
关键词： optogenetics,Implantable devices,micro-light-emitting diodes (LEDs),wireless operation
更新于2025-09-09 09:28:46