Optimization of AlGaN-Based Deep Ultraviolet Laser Diodes with Graded Rectangular Superlattice Electron Blocking Layer and Graded Trapezoidal Superlattice Hole Blocking Layer

Journal of Russian Laser Research - To improve the carrier confinement capability and optimize the performance of deep ultraviolet laser diodes (DUV-LDs), we propose the graded rectangular...     

Reduction of Electron Leakage in a Deep Ultraviolet Nitride Laser Diode with a Double-Tapered Electron Blocking Layer

A double-tapered AlGaN electron blocking layer (EBL) is proposed to apply in a deep ultraviolet semiconductor laser diode. Compared with the inverse double-tapered EBL, the laser with the double-tapered EBL shows a higher slope efficiency, which indicates that effective enhancement in the transportation of electrons and holes is achieved. Particularly, comparisons among the double-tapered EBL, the inverse double-tapered EBL, the singletapered EBL and the inverse single-tapered EBL show that the double-tapered EBL has the best performance in terms of current leakage.     

Effects of the Stepped-Doped Lower Waveguide and a Doped p-Cladding Layer on AlGaN-Based Deep-Ultraviolet Laser Diodes

Journal of Russian Laser Research - The performance of deep ultraviolet (DUV) laser diodes (LDs) may be affected by structural variations in the composition of AlGaN devices. In this work, we...     

Low-Threshold-Current and High-out-Power 660 nm Laser Diodes with a p-GaAs Current Blocking Layer for DVD-RAM/R

We investigate a new structure of high-power 660-nm AlGaInP laser diodes. In the structure, a p-GaAs layer is grown on the ridge waveguide serving as the current-blocking layer, and nonabsorbing windows are only fabricated near the cavity facets to increase the catastrophic-optical-damage level. Stable fundamental mode operation was achieved at up to 80roW without kinks, and the maximum output power was 184roW at 22~C. The threshold current was 40 mA.     

The Transport Mechanisms of Reverse Leakage Current in Ultraviolet Light-Emitting Diodes

The transport mechanisms of the reverse leakage current in the UV light-emitting diodes(380 nm) are investigated by the temperature-dependent current-voltage measurement first.Three possible transport mechanisms,the space-limited-charge conduction,the variable-range hopping and the Poole-Frenkel emission,are proposed to explain the transport process of the reverse leakage current above 295 K,respectively.With the in-depth investigation,the former two transport mechanisms are excluded.It is found that the experimental data agree well with the Poole-Frenkel emission model.Furthermore,the activation energies of the traps that cause the reverse leakage current are extracted,which are 0.05 eV,0.09 eV,and O.lleV,respectively.This indicates that at least three types of trap states are located below the bottom of the conduction band in the depletion region of the UV LEDs.     

电子阻挡层Al组分对GaN基蓝光激光二极管光电性能的影响

采用SiLENSe（Simulator of light emitters based on nitride semiconductors）软件仿真研究了Al_xIn_yGa_1-x-yN电子阻挡层（EBL）Al组分渐变方式对GaN基激光二极管（LD）光电性能的影响,实现了提高输出功率和电光转换效率的目的。文中提出的四种Al组分渐变方式分别是传统均匀组分、右阶梯渐变组分（0～0.07～0.16）、三角形渐变组分（0～0.16～0）、左阶梯渐变组分（0.16～0.07～0）。结果表明,与传统均匀组分EBL结构相比,Al组分阶梯渐变Al_xIn_yGa_1-x-yN EBL LD导带底的电子势垒显著提高,价带顶的空穴势垒降低。这主要是由于该结构能有效抑制电子泄漏和提高空穴注入效率,从而提高有源区载流子浓度,进而提高有源区辐射复合效率。当注入电流为0.48 A时,采用Al组分阶梯渐变Al_xIn_yGa_1-x-y...     

Organic Light-Emitting Diodes with Magnesium Doped CuPc as an Efficient Electron Injection Layer

Bright organic electroluminescent devices are developed using a metal-doped organic layer intervening between the cathode and the emitting layer. The typical device structure is a glass substrate/indium-tin oxide （ITO）/copper phthalocyanine （CuPc）/N,N＇-bis-（1-naphthl）-diphenyl-1,1＇-biphenyl-4,4＇-diamine （NPB）/Tris（8-quinolinolato） aluminum（Alq3）/Mg-doped CuPc/Ag. At a driving voltage of 11 V, the device with a layer of Mg-doped CuPc （1：2 in weight） shows a brightness of 4312cd/m^2 and a current efficiency of 2.52cd/A, while the reference device exhibits 514 cd/m^2 and 1.25 cd/A.     

量子垒高度对深紫外LED调制带宽的影响

AlGaN基深紫外LED由于具有高调制带宽和小芯片尺寸,在紫外光通信领域受到越来越多的关注.本研究通过改变生长AlGaN量子垒层的Al源流量,生长了三种具有不同量子垒高度的深紫外LED,研究了量子垒高度对深紫外LED光电特性和调制特性的影响.研究发现,随着量子垒高度的增加,深紫外LED的光功率出现先增加后减小的趋势,量...     

具有电流阻挡层的不同GaN基LED的光电特性(英文)

研究对比了InGaN/GaN多量子阱发光二极管中p电极下的不同SiO2电流阻挡层的光电特性。6种样品被分为3组:普通表面、表面粗化、表面粗化+边墙腐蚀。每组都有两种结构,一种具有电流阻挡层,另一种没有电流阻挡层。每组中,具有电流阻挡层的LED在20 mA下的正向电压分别为3.156,3.282,3.284 V,略高于不含电流阻挡层的样品(Vf=3.105,3.205,3.210 V).但是,具有电流阻挡层的LED的光效和光功率要优于无电流阻挡层的器件,在20 mA下的光功率分别提高了10.20%、12.19%和11.49%。这些性能的提升都要归功于电流阻挡层良好的电流扩展效应,同时电流阻挡层还可以减小p电极下的寄生光吸收。     

采用复合空穴注入层提高有机电致发光器件的性能

制备了以Ag/SAM/m-MTDATA为复合空穴注入层的NPB/Alq₃双层异质结发光器件,研究了器件的性能并与传统的器件进行了对比。考察了银膜厚度的变化对器件性能的影响。研究了光谱窄化以及微腔效应对器件的影响。研究结果表明:在ITO表面制备4-FTP自组装单分子膜修饰的5 nm厚的金属银膜,可以在保持阳极透明性的基础上,增强空穴的注入,改善界面的形貌,进而提高器件性能。制备的ITO/Ag/SAM/m-MTDATA/NPB/Alq₃/LiF/Al器件的启亮电压为4 V,最 大电流效率为6.9 cd/A, 最大亮度为34 680 cd/m²(12 V);优于以ITO为阳极的对比器件(25 300 cd/m² @12 V)。     

All-Optical Switching Using Fabry-Perot Laser Diodes(Invited paper)

In this paper, we investigate all-optical packet switching using a multi-wavelength mutual injection-locked Fabry-Perot laser diode. We observe error-free packet-switching of a 10 Gb/s signal with an extinction ratio of 16.9.     

Influence of Blocking Interlayer in Blue Organic Light-Emitting Diodes with Different Thicknesses of Emitting Layer and Interlayer

A series of blue organic light-emitting diodes with electron or hole blocking interlayer are fabricated.Different structures of blocking interlayers can influence the position of the recombination zone due to the fact that they confine carriers in different ways.We find that the double hole blocking interlayer structure can balance carrier injection more effectively.Its power and current efficiency are more stable and the current efficiency value is30.2cd/A at 1000cd/m2.Decreasing the thicknesses of the emitting layer and interlayers is in favor of the power efficiency.The performance of the device is also affected by changing the interlayer position when we use hole and electron blocking material as interlayers simultaneously.     

Bistable Optical Devices Using Laser Diodes Coupled to Interference Filters

A bistable optical device was demonstrated by using the longitudinal mode hopping of the laser diode and the narrow transmission spectrum of an interference filter. The device is capable of converting changes in the wavelength of the laser diode into changes in intensity by transmitting it through the filter. Exclusive OR operation was observed with the use of triple signal outputs. In addition, an optical switch-off phenomenon was confirmed by directly injecting a pulse 500 ps wide into an external dye laser.     

电子传输层厚度及阻塞层对量子点发光二极管性能的影响

针对量子点发光二极管(QLED)中载流子注入不平衡的问题,对空穴和电子在量子点层的注入速率进行了研究。制备了不同电子传输层厚度、结构为ITO/PEDOT∶PSS/Poly-TPD/QDs/Alq3/Al的QLED样品。Alq_3厚度由25 nm逐步递增至45 nm时,器件的开启电压升高,器件均发出量子点的红光。当Alq_3厚度为30nm时,器件的电流效率最高。此时,空穴和电子在量子点层的注入速率达到相对平衡。为进一步研究器件的发光特性,在QDs和Alq_3接触界面嵌入电子阻塞层TPD。研究发现,当TPD的厚度为1 nm时,器件发出红光;当TPD厚度为3 nm和5 nm时,器件开始出现绿光。实验结果表明,在选取电子阻塞层时,应选择LUMO较低的材料且阻塞层的厚度必须很薄。     

Ultrafast Dynamics Using Free Electron Laser Sources

As avid readers of SRN know, free electron lasers have recently emerged as important synchrotron-radiation-based tools for a broad range of scientific studies. The combination of their short wavelength (from VUV to hard X-ray) with their exceedingly brief pulses (down to a few femtoseconds), high pulse energy, and coherence makes them particularly useful tools for studying ultrafast dynamics with chemical specificity and atomic-scale structural sensitivity.     

苯和苯胺在深紫外光照射下的电离和解离

本文利用自主研制的反射式飞行时间质谱仪结合177.3 nm深紫外激光研究了苯和苯胺分子的光电离与光解离过程. 质谱实验发现苯在177.3 nm皮秒激光作用下发生高效电离并观测到不对称C-C键解离形成的以C₄H₃⁺为主的较小碎片峰. 相比之下,苯胺的深紫外光电离中主要产生一个C₅H₆^+·离子自由基和一个较小丰度的C₆H₆^+·碎片,分别对应于CNH分子和NH自由基的去除. 结合第一性原理计算,诠释了苯和苯胺这两个仅有一个氨基差异的分子光解离路径,揭示苯和苯胺分子中氢原子转移对于C-C或C-N键断裂的关键重要作用.     

以Liq作为电子注入层的高效有机电致发光器件

利用Liq(8-hydroxy-quinolinato lithium)作电子注入层，制备了结构为ITO(indium tin oxide)／TPD(N，N′-diphenyl-N，N′—bis(3—methylphenyl)—1，1′biphenyl-4，4′diamine)／Alq3(tris-(8-hydroxy-quinolinato)aluminum)／Liq／Al的电致发光器件。实验表明，以Liq作为电子注入层器件的效率约为无Liq器件的5倍。其原因可归于Liq在金属铝电极与Alq3有机层之间产生偶极层，从而形成铝与有机层间的欧姆接触，使电子注入效率大幅提高。     

Electron in an Ultrashort Laser Pulse

After the classical approach to acceleration of a charged particle by -form impulsive force, we consider the corresponding quantum theory based on the Volkov solution of the Dirac equation. We determine the modified Compton formula for frequency of photons generated by the scattering of the -form laser pulse on the electron in a rest frame.