InGaN基蓝色发光二极管量子阱阻挡层的优化设计

计算比对了不同垒层构型量子阱的极化电场,对极化场下能级结构、载流子浓度分布、自发辐射复合速率和缺陷所造成的Shockley-Reao-Hall(SRH)非辐射复合速率进行了研究,确定内建电场引起的量子阱区域载流子浓度分布均匀性是影响器件效能高低的关键因素.对大电流下晶格优化的A10.02In0.1Ga0.88N四元材料作为量子阱垒层的器件效能和发光特性下降的原因进行了深入分析,同时提出了具体的解决方法.     

Enhancement of Light Extraction Efficiency of Gallium Nitride Flip-Chip Light-Emitting Diode With Silicon Oxide Hemispherical Microlens on its Back

Silicon oxide (SiO₂) hemispherical microlens with the density of 8.2 times 10⁸ cm^-2 has been formed on a sapphire substrate of gallium nitride (GaN) light-emitting diode (LED) by liquid phase deposition to enhance the light extraction efficiency. For flip-chip LED, the SiO₂ microlens exhibits 1.25 times enhancement of optical output power. In comparison of the conventional LED, there is 61% enhancement for flip-chip LED with a SiO₂ microlens.     

应力补偿型InGaN-AlGaN量子阱发光二极管结构优化研究

薄的应力补偿层AlGaN的引进对InGaN量子阱结构的发光二极管输出功率和内量子效率的影响被详细考察.由理论模拟结果得知,不管是在低温还是高温,合适的应力补偿层引进都能极大改善LED器件输出功率和内量子效率.应力补偿层AlGaN的加入导致器件漏电流的降低被认为是器件效能提高的主要原因.定量优化AlGaN应力补偿层的厚度和其中Al的含量在这里也被探讨研究.计算结果表明,当应力补偿型InGaN-AlGaN量子阱结构中AlGaN厚度为1nm,Al含量为0.25时,能够获得最大的发光功效和内量子效率.     

基于表面等离子波耦合的流体波导光栅耦合器

提出了一种由金属光栅和流体光波导结构组成的,基于表面等离子波耦合的光栅耦合器。利用光栅的衍射效应,将金属光栅与介质分界面之间产生的表面等离子波耦合到流体光波导中,并且能够沿着流体光波导稳定地向前传播。通过采用基于有限时域差分算法的FDTD Solutions软件对光栅耦合器进行了参数优化及特性分析,通过优化使该结构在650 nm波长下的耦合效率达到56%。此外,由于该结构对TE偏振光和TM偏振光的选择比达到70∶1,因此具有偏振器的功能。同时由于TE偏振光耦合频谱的频带宽度仅为20 nm,该结构还具有窄带滤波的作用。此外,还研究了光栅结构参数、入射角以及流体折射率对耦合频谱的影响。     

Study of an AlGaInP-Based Light-Emitting Diode With a Modulation-Doped Multiquantum-Well (MD-MQW) Structure

An AlGaInP-based multiquantum-well (MQW) light-emitting diode (LED) with an n-type modulation-doped (MD) structure, grown by metal-organic vapor-phase epitaxy, is fabricated and studied. Experimental results indicate that a lower turn-on voltage and dynamic resistance, higher output power, and smaller wavelength shift, as compared to a conventional undoped-MQW LED, are obtained. The studied n-type MD-MQW LED also exhibits a higher external quantum efficiency of 7.2% and a larger maximum light output power. The junction temperature of the studied MD-MQW LED also shows a 12 degC reduction, at 200 mA, as compared to a conventional one. These positive results are mainly attributed to the presence of a higher electron concentration in the MD-MQW active region.     

Solution-Processed and Room-Temperature Spin Light-Emitting Diode Based on Quantum Dots/Chiral Metal-Organic Framework Heterostructure

Spin optoelectronics is an indispensable key for the future development of spintronics. In conventional spin light emitting diodes (LEDs), spin-polarized carrier pairs are injected electrically into the light emitting layer and create circularly polarized light (CPL). Generally, spin-polarized carriers are accomplished using ferromagnetic contacts or applying an external magnetic field, which will produce several drawbacks, including low temperature operation, low spin-polarized carriers injection efficiency, etc. To circumvent the existing shortcomings, here, an alternative approach is proposed and achieves spin-polarized LEDs at room temperature based on quantum dots (QDs)/chiral metal-organic framework heterojunction without using ferromagnetic contacts or magnetic fields. The spin-polarized injected layer composed of self-assembled monolayer (SAM)/Chiral-MOF ([Sr(9,10-adc)(DMAc)2]n)) film, which produces spin-polarized holes with spin orientation, determining the polarization and strength of circularly polarized electroluminescence (CP-EL). The spin-QLED emits CP-EL at a rate of 12.24% efficiency, which provides an excellent alternative to generate new functionality for conventional QLEDs. The approach is anticipated to be very useful, enabling to offer a general methodology for generating not yet realized spin optoelectronic devices.     

半导体激光器光束耦合效率研究

在远距离无线光通信中,接收点光功率与光束发散角平方成反比。为了获得小的光束发散角和大的功率耦合效率,必须研究光束准直系统与耦合效率的关系。根据非傍轴远场光分布理论,用光线追迹法对半导体激光器光束准直系统中的功率耦合效率进行研究,给出半导体激光器光束耦合效率的计算方法,并进行计算机模拟。这里的研究结果对半导体激光器光束准直系统设计具有一定的指导作用。     

On a GaN-Based Light-Emitting Diode With a p-GaN/i-InGaN Superlattice Structure

An interesting GaN-based light-emitting diode (LED) with a ten-period i-InGaN/p-GaN (5-nm/5-nm) superlattice (SL) structure, inserted between a multiple-quantum-well structure and a p-GaN layer, is fabricated and studied. This inserted SL can be regarded as a confinement layer of holes to enhance the hole injection efficiency. As compared with a conventional LED device without the SL structure, the studied LED exhibits better current-spreading performance and an improved quality. The turn-on voltage, at 20 mA, is decreased from 3.32 to 3.14 V due to the reduced contact resistance as well as the more uniformity of carrier injection. A substantially reduced leakage current (10^-7-10^-9 A) and higher endurance of the reverse current pulse are found. As compared with the conventional LED without the SL structure, the significant enhancement of 25.4% in output power and the increment of 5% in external quantum efficiency are observed.     

Extraction Efficiency Enhancement of GaN-Based Light-Emitting Diodes by Microhole Array and Roughened Surface Oxide

The light-output power of GaN-based light-emitting diodes (LEDs) was enhanced by microhole array pattern and roughened $hbox{GaO}_{x}$ film grown on the exposed surface. The $hbox{GaO}_{x}$ film was grown by photoelectrochemical (PEC) oxidation via $hbox{H}_{2}hbox{O}$ and formed a naturally rough oxide surface and $hbox{GaO}_{x}/hbox{GaN}$ interface. Compared with that of conventional broad-area LEDs, the output power of the microhole array LED and the surface-oxidized microhole array LED increased by 1.38 and 1.82 times at 20-mA forward current, respectively. The results show that the microhole array pattern with the roughened surface oxide method could significantly enhance light extraction efficiency and be a candidate for manufacturing high-efficient low-cost GaN-based LEDs.      

Efficiency Enhancement of Light Extraction in LED With a Nano-Porous GaP Surface

Electrodeless photoelectrochemical etching is developed to produce a nano-porous n-GaP surface. Pores of diameter 300-700 nm are distributed on the surface with a density 1.2 times 10⁸ cm^-2. Such a porous surface structure exhibits a short mean free path for the transport of visible light and enhances photon scattering in a red AlInGaP-based light-emitting device. The efficiency of extraction of light emitted from the active layer becomes about 30%-50% greater than that without an etching treatment at a current of 20-40 mA.     

低阈值高效率InAIGaAs量子阱808nm激光器

以Al0.3Ga0.7 As／InAlGaAs／Al0.3Ga0.7As压应变量子阱代替传统的无应变量子阱作为有源区，实现降低808nm半导体激光器的阈值电流，并提高器件的效率。首先优化设计了器件结构，并利用金属有机物化学气相淀积（MOCVD）进行了器件的外延生长。通过优化外延生长条件，保证了5．08cm片内的量子阱（OW）光致发光（PL）光谱峰值波长均匀性达0．1％。对于条宽为50／zm，腔长为750／zm的器件，经镀膜后的阈值电流为81mA，斜率效率为1．22W／A，功率转换效率达53．7％。变腔长实验得到器件的腔损耗仅为2cm^-1，内量子效率达90％。结果表明，压应变量子阱半导体激光器具有更优异的特性。     

低阈值高效率InAlGaAs量子阱808 nm激光器

以Al0.3Ga0.7As/InAlGaAs/Al0.3Ga0.7As压应变量子阱代替传统的无应变量子阱作为有源区,实现降低808 nm半导体激光器的阈值电流,并提高器件的效率。首先优化设计了器件结构,并利用金属有机物化学气相淀积(MOCVD)进行了器件的外延生长。通过优化外延生长条件,保证了5.08 cm片内的量子阱(QW)光致发光(PL)光谱峰值波长均匀性达0.1%。对于条宽为50μm,腔长为750μm的器件,经镀膜后的阈值电流为81mA,斜率效率为1.22 W/A,功率转换效率达53.7%。变腔长实验得到器件的腔损耗仅为2 cm-1,内量子效率达90%。结果表明,压应变量子阱半导体激光器具有更优异的特性。     

高效率808 nm激光器的数值模拟研究

分析了提高激光器电光转换效率的几种途径,认为降低激光器工作电压、串联电阻和阈值电流可以提高激光器转换效率.分别对Ga0.5InP和AlxGaAs对称波导激光器进行了模拟,结果表明,AlxGaAs材料体系(AlxGaAs/AlxGaAs/InGaAsP)激光器的各种参数均优于Ga0.5InP材料体系((AlxGa)0.5InP/Ga0.5InP/InGaAsP)激光器,并在模拟的基础上制备出了相应的激光器.依据模拟结果和器件结果分析得出,增大波导层掺杂浓度可以降低激光器的工作电压和串联电阻;改变波导层组分为渐变值时可降低激光器阈值电流,从而增大激光器转换效率.     

注入型多孔硅基发光二极管的研究进展

主要评述了Schottky结和PN结多孔硅基发光二极管的结构和性能及其研究进展。讨论了器件界面态对其性能的影响。最后分析了目前器件研究中存在的亟需解决的问题以及解决方法。     

量子阱太阳能电池的外量子效率

通过实验比较了砷化镓量子阱太阳能电池与不含量子阱结构的普通砷化镓太阳能电池的外量子效率. 结果表明,量子阱太阳能电池吸收光子的波长从870nm 扩展到了1000nm. 当波长小于680nm时,量子阱太阳能电池的外量子效率低于普通太阳能电池;而当波长大于于680nm时,量子阱太阳能电池的外量子效率高于普通太阳能电池. 对这个现象给出了解释,并对用量子阱太阳能电池代替三结电池的中间子电池的可能性进行了讨论.     

量子阱太阳能电池的外量子效率

通过实验比较了砷化镓量子阱太阳能电池与不含量子阱结构的普通砷化镓太阳能电池的外量子效率.结果表明,量子阱太阳能电池吸收光子的波长从870nm扩展到了1000nm.当波长小于680nm时,量子阱太阳能电池的外量子效率低于普通太阳能电池;而当波长大于于680nm时,量子阱太阳能电池的外量子效率高于普通太阳能电池.对这个现象给出了解释,并对用量子阱太阳能电池代替三结电池的中间子电池的可能性进行了讨论.     

On an AlGaInP Light-Emitting Diode With a Modulation-Doped Multiquantum-Well (MD-MQW) Structure

An interesting AlGaInP multiquantum-well (MQW) light-emitting diode (LED) with an n-type modulation-doped (MD) structure, grown by low-pressure metal–organic vapor-phase epitaxy (LP-MOVPE), is fabricated and studied. This n-type MD-MQW LED exhibits lower dynamic resistance, higher luminescence, and higher luminous efficiency than those of a conventional undoped-MQW LED. Experimental results show a higher luminous efficiency of 16.05 lm/W and higher luminescence of 2.53 lm are obtained for the MD-MQW LED which are superior to the corresponding values of 14.49 lm/W and 2.04 lm for the undoped-MQW LED under dc operation. In addition, the n-type MD-MQW LED exhibits a higher quantum efficiency of 7.2% under dc operation as compared with the 6.7% of the undoped-MQW LED. The reduced junction temperature of 12 $~{^circ}$C at 200 mA is also acquired for the MD-MQW LED. Moreover, the brightness reliability of this new device is found to be comparable to the undoped-MQW LED. These positive results could be attributed to the presence of a higher electron concentration in the active region of the MD-MQW structure which causes the suppression of electron thermal velocity especially at a high level injection condition, and a reduced junction heating effect.      

光纤表面等离子体波共振温度传感器的研究

根据液体折射率随温度变化而改变的特性，提出了一种基于表面等离子体波共振(SPR)效应的新型光纤温度传感器，分析了表面等离子体波共振光纤探头感应环境温度变化的原理。对表面等离子体波共振探头结构进行了优化设计，并进行了相关实验，为实现高折射率液体介质的感温测试和扩大测温范围提供依据。通过自行设计的一套光纤温度传感测试系统，得到系统输出的表面等离子体波共振光谱信号随温度变化的特性曲线，并提出对共振波长和最小光强反射率进行实时双参数测量的方法。实验结果表明，该测试系统具有结构简单、全光纤化、易远程测量等优点。     

双势垒量子阱薄膜力电耦合特性实验

用分子束外延方法在(001)GaAs衬底上生长了AlAs/InGaAs双势垒量子阱薄膜结构.介绍了量子阱薄膜在(110)与(110)方向单轴压应力作用下的力电耦合实验,测试出量子阱薄膜在室温下随着外加压力变化的I-V曲线.测试结果表明:量子阱薄膜I-V曲线的共振峰在(110)方向单轴应力作用下向正偏压方向漂移,在(110)方向应力作用下向负偏压方向偏移,并分析了量子阱薄膜力电耦合效应的物理成因.该结果与基于量子阱力电耦合特性的介观压阻理论的研究结果相吻合.