GaN基肖特基二极管的场板工程

The practical design of GaN-based Schottky barrier diodes（SBDs） incorporating a field plate（FP） structure necessitates an understanding of their working mechanism and optimization criteria.In this work,the influences of the parameters of FPs upon breakdown of the diode are investigated in detail and the design rules of FP structures for GaN-based SBDs are presented for a wide scale of material and device parameters.By comparing three representative dielectric materials（SiO₂,Si₃N₄ and Al₂O₃） selected for fabricating FPs,it is found that the product of dielectric permittivity and critical field strength of a dielectric material could be used as an index to predict its potential performance for FP applications.     

Influence of GaN material characteristics on device performance for blue and ultraviolet light-emitting diodes

An analysis of blue and near-ultraviolet (UV) light-emitting diodes (LEDs) and material structures explores the dependence of device performance on material properties as measured by various analytical techniques. The method used for reducing dislocations in the epitaxial III-N films that is explored here is homoepitaxial growth on commercial hybride vapor-phase epitaxy (HVPE) GaN substrates. Blue and UV LED devices are demonstrated to offer superior performance when grown on GaN substrates as compared to the more conventional sapphire substrate. In particular, the optical analysis of the near-UV LEDs on GaN versus ones on sapphire show substantially higher light output over the entire current-injection regime and twice the internal quantum efficiency at low forward current. As the wavelength is further decreased to the deep-UV, the performance improvement of the homoepitaxially grown structure as compared to that grown on sapphire is enhanced.     

具有背面反射镜的GaN基高压LED

High-voltage light-emitting diodes （HV-LED） with backside reflector, including Ti305/SiO2 distributed Bragg reflector （DBR） or hybrid reflector combining DBR and Al or Ag metal layer, are investigated using Monte Carlo ray tracing method. The hybrid reflector leads to more enhancement of light-extraction efficiency （LEE）. Moreover, the LEE can also be improved by redesigning the thicknesses of DBR. HV-LED with four redesigned DBR pairs （4-MDBR）, and those with a hybrid reflector combining 4-MDBR and Al metal layer （4-MDBR-Al）, are fabricated. Compared to 4-MDBR, the enhancement of light-output power induced by 4-MDBR-A1 is 4.6%, which is consistent with the simulated value of 4.9%.     

High efficiency pure white organic light-emitting diodes using a diphenylaminofluorene-based blue fluorescent material

High efficiency pure white organic light-emitting diodes (WOLEDs) were developed using a highly efficient diphenylaminofluorene-based deep blue fluorescent material (DAF). A high quantum efficiency of 7.1% with color coordinates of (0.15, 0.18) were obtained from the DAF-doped blue device, which was then combined with phosphorescent red/green devices. A mixed interlayer was used to control the color coordinates and charge balance in the emitting layer of the WOLEDs. The pure white hybrid WOLEDs showed a high quantum efficiency of 12.3%.     

Anomalous luminescence efficiency enhancement of short-term aged GaN-based blue light-emitting diodes

The origin of anomalous luminescence efficiency enhancement of short-term aged GaN-based blue light-emitting diodes was studied. We found that the intensity of the electroluminescence and photoluminescence spectra were both increased in the very beginning period of aging. With the help of a rate-equation model, we concluded that this kind of luminescence efficiency enhancement is a joint effect of the defect reduction in active layers and the changes out of active layers, for example the Mg acceptor annealing.     

Deep blue phosphorescent organic light-emitting diodes with excellent external quantum efficiency

Highly efficient deep blue phosphorescent organic light-emitting diodes (PHOLEDs) using two heteroleptic iridium compounds, (dfpypy)₂Ir(acac) and (dfpypy)₂Ir(dpm), as a dopant and 9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)diphenylphosphine oxide as a host material have been developed. The electroluminescent device of (dfpypy)₂Ir(dpm) at the doping level of 3 wt% shows the best performance with external quantum efficiency of 18.5–20.4% at the brightness of 100–1000 cd/m² and the color coordinate of (0.14, 0.18) at 1000 cd/m².     

白光有机电致发光器件发光稳定性研究

基于红绿/蓝双发光层,制作了结构为ITO/MoO ₃(10nm)/NPB(40nm)/TCTA(10nm)/CBP:R-4B(2%):GIR1(14%,X nm)/mCP:Firpic(8%,Y nm/BCP(10nm)/Alq₃(40nm)/LiF(1nm)/Al( 100nm)的白色全磷光有机电致发光器件(OLED),通过 调节红绿发光层的厚度X与蓝光发光层的厚度Y,研究了不同发光层厚度器件发 光性能的影响。研究发现:当X 为23nm、Y为7nm时,器件的光效和色坐标都具有 很高的稳定性,在电压分别为5、 10和15V时,色坐标分别为(0.33,0.37)、(0.33,0. 37)和(0.34,0.38);在电压为 5V时,电流密度为0.674mA,亮度为158.7cd ,最大电流效率为26.87cd/A;利用电子阻 挡材料TCTA和空穴阻挡材料BCP能够显著提高载流子的复合效率。分析认为:发光层顺序 为红绿/蓝时,更有利于蓝光的出射,从而使白光的色坐标更稳定。     

氮化镓基蓝、绿光LED中游工艺技术产业化研究

氮化镓基蓝、绿光LED在光显示及未来的白光照明领域具有广阔的应用前景,中国科学院半导体研究所和深圳市方大国科光电技术公司利用双方各自的技术优势和资金管理优势,实现了氮化镓基蓝、绿光LED中游工艺技术产业化,目前产品已经批量上市销售。     

对具有 AlGaN 渐变垒的蓝光LED的研究

在此项研究中,我们对具有渐变AlGaN垒的蓝光LED进行了一系列的分析。其中,用APSYS模拟出了载流子分布、能带图、静电场分布及其光输出功率。模拟结果显示具有渐变AlGaN垒的蓝光LED相比普通结构的LED性能更好。     

Near-infrared organic light-emitting diodes of pure fluorescence emission using small-molecule boron-dipyrromethene derivative

Near-infrared (NIR) light has various applications, such as in cameras and sensors. Organic light-emitting diodes (OLEDs), which are characterized by their thinness, lightweight, and flexibility, have potential application in various devices requiring light emission in the NIR region. In this study, we focused on the wavelength range of 700–1000 nm, which is called the “first optical window” in NIR light. Furthermore, we investigated the optical properties of a low-molecular-weight boron-dipyrromethene derivative (BODIPY-Ph), which has been reported to possess NIR absorption properties as well as the luminescence properties of BODIPY-Ph-based OLEDs in the NIR region. An acetone solution of BODIPY-Ph showed 52.3% photoluminescence quantum yield and the apparent external quantum efficiency of the OLED in the NIR region was high at 1.87%, which is one of the highest values when using OLEDs that are metal-free and use pure fluorescence emission without using triplet.