带间级联激光器电子注入区优化研究(特邀)EI北大核心CSCD

带间级联激光器有源区内部的物理机制复杂,尚未得到充分研究。优化了电子注入区结构,通过减小InAs/AlSb啁啾超晶格中InAs量子阱的厚度促进电子向光增益区的注入,在较低的电子注入区掺杂浓度下满足了光增益区电子数和空穴数基本相等的注入平衡条件,降低了有源区中自由载流子吸收和杂质散射造成的光损耗。采用该有源区结构的带间级联激光器实现了较好的室温激射性能,腔长4 mm、脊宽20μm且腔面未镀膜器件的阈值电流为200 mA,单腔面出光功率为55 mW。通过分析2~5 mm不同腔长器件的电压-电流-光功率性能,得到器件的波导损耗仅为3 cm^(-1),有源区载流子寿命为0.7 ns。     

带间级联激光器电子注入区优化研究(特邀)

带间级联激光器有源区内部的物理机制复杂,尚未得到充分研究.优化了电子注入区结构,通过减小InAs/AlSb啁啾超晶格中InAs量子阱的厚度促进电子向光增益区的注入,在较低的电子注入区掺杂浓度下满足了光增益区电子数和空穴数基本相等的注入平衡条件,降低了有源区中自由载流子吸收和杂质散射造成的光损耗.采用该有源区结构的带间级...     

量子阱结构对有机电致发光器件效率的影响

实验中共制备了五种有机量子阱结构电致发光器件,分别对这五种量子阱结构器件的电致发光特性进行了研究,分析了量子阱结构的周期数和势垒层的厚度对器件电学性能的影响.实验结果表明适当周期数的量子阱结构器件的亮度和电流效率比传统的三层结构器件的要大,主要原因是量子阱结构对电子和空穴的限制作用,这种限制作用提高了电子和空穴在发光层中形成激子和复合的概率,从而提高了发光的亮度和效率.当改变阱结构器件中势阱层的厚度时,也会对器件的亮度和效率产生影响,采用适当的势阱层厚度能够提高器件的亮度和效率. 关键词： 量子阱结构 电致发光 电流效率 光谱     

半导体量子电子和光电子器件

本阐述了半导体异质结构电子的量子特性,如电子波输运,库仑阻塞效应等,介绍了几种新颖,典型的量子电子器件和量子光电子器件的物理模型和基本原理,这些器件包括了单电子晶体管,共振隧穿二极管,高电子迁移率晶体管,δ掺杂场效应晶体管,量子点元胞自动机,量子阱红外探测器,埋沟异质结半导体激光器,量子级联激光器等,给出了作在半导体量子器件物理方面的最新研究结果。     

带间级联激光器: 从原始概念到实际器件

本文讨论了带间级联激光器中相关的概念,材料体系和生长,器件制造,量子阱结构和物理过程,回顾了它们从原始的概念到实际器件的发展历程。介绍了最近的进展和目前的状态,并讨论了带间级联激光器的未来前景。     

半导体量子电子和光电子器件

本文阐述了半导体异质结构电子的量子特性 ,如电子波输运、库仑阻塞效应等。介绍了几种新颖、典型的量子电子器件和量子光电子器件的物理模型和基本原理。这些器件包括了单电子晶体管、共振隧穿二极管、高电子迁移率晶体管、δ掺杂场效应晶体管、量子点元胞自动机、量子阱红外探测器、埋沟异质结半导体激光器、量子级联激光器等。给出了作者在半导体量子器件物理方面的最新研究结果。     

量子阱级联激光器

介绍了一种新型的工作于４．２５μｍ的半导体激光器－量子阱级联激光器，这种新型激光器是单极性的，它发光仅依赖于电子而并非正负两种电荷，介绍了这种激光器的结构，工作原理和激光特性。     

Si/SiGe量子级联激光器的能带设计

详细论述Si/SiGe量子级联激光器的工作原理，通过对比找到一组合适的Si，Ge和SiGe合金的能带参数，进而应用6×6 k·p方法计算了不同阱宽、不同Ge组分Si/Si_1-xGe_x/Si量子阱价带量子化的空穴能级本征值及其色散关系，分析Si/Si_1-xGe_x/Si量子阱空穴态能级间距随阱宽和组分的变化规律，最后应用计算结果讨论了Si/SiGe量子级联激光器有源区的能带设计，有益于优化Si /SiGe量子级联激光器结构. 关键词： 硅锗材料 量子级联激光器 子带跃迁 k·p方法')" href="#">k·p方法     

氧化锌锡作为电子传输层的量子点发光二极管

本文研究了以胶状量子点作为发光层和有机/无机混合材料作 为电子-空穴传输层的电致发光二极管器件. CdSe 量子点以薄膜的形式夹在无机氧化锌锡电子传输层和有机TPD空穴传输层中间构成三明治结构. 氧化锌锡电子传输层采用磁控溅射实现, 有机TPD空穴传输层和量子点发光层则采用旋涂的方法制备, 得到的QD-LEDs器件结构界面陡峭、表面平整. 光电特性表征结果显示器件的电致发光具有良好的单色性、低的开启电压, 利 用具有高电子迁移率和低载流子浓度的无机氧化锌锡薄膜作为电子传输层可 以实现器件在大气环境下稳定、明亮的电致发光. 本文分析了器件的工作机理并通过改变氧化锌锡的电导率达到控制器件中电子和空穴的注入比的目的, 优化了器件的光电性能. 关键词： 量子点 氧化锌锡 电致发光 电子传输层     

单模带间级联激光器（特邀）

基于锑化物的带间级联激光器同时具有带间跃迁的高增益和级联结构的高量子效率,是中红外波段重要的相干光源,其功耗低于其它中红外半导体激光器,因而单模带间级联激光器在基于激光吸收光谱技术的高分辨气体检测和化学传感等领域具有很大的优势。目前利用Bragg光栅实现波长选择的单模分布反馈带间级联激光器已经实现商品化,但是,与同样有源区结构的Fabry-Pérot腔带间级联激光器最高600 mW的出光功率相比,单模功率最高55 mW,损耗较大。对几种不同结构的分布反馈带间级联激光器的性能进行对比分析,探讨这类单模中红外激光器损耗的主要来源以及改进思路。此外,介绍了垂直腔面发射和光子晶体带间级联激光器的进展,并与分布反馈带间级联激光器的性能进行比较,讨论其优缺点及适用的场景。     

Nanoscopically resolved dynamic charge‐carrier distribution in operating interband cascade lasers

Dynamic charge carriers play a vital role in active photonic quantum/nanodevices, such as electrically pumped semiconductor lasers. Here we present a systematic experimental study of gain‐providing charge‐carrier distribution in a lasing interband cascade laser. The unique charge‐carrier distribution profile in the quantum‐well active region is quantitatively measured at nanometer scales by using a noninvasive scanning voltage microscopy technique. Experimental results clearly confirm the accumulation and spatial segregation of holes and electrons in the beating heart of the device. The measurement also shows that the charge‐carrier density is essentially clamped in the presence of stimulated emission at low temperatures. The threshold charge‐carrier density exhibits a linear but fairly weak temperature dependence, in contrast to the exponential temperature dependence of the threshold current. The experimental approach will lead to a deeper understanding of fundamental processes that govern the operation and performance of nanoelectronic devices, quantum devices and optoelectronic devices.

     

Gain recovery dynamics and photon-driven transport in quantum cascade lasers

Quantum cascade lasers are semiconductor devices based on the interplay of perpendicular transport through the heterostructure and the intracavity lasing field. We employ femtosecond time-resolved pump-probe measurements to investigate the nature of the transport through the laser structure via the dynamics of the gain. The gain recovery is determined by the time-dependent transport of electrons through both the active regions and the superlattice regions connecting them. As the laser approaches and exceeds threshold, the component of the gain recovery due to the nonzero lifetime of the upper lasing state in the active region shows a dramatic reduction due to the onset of quantum stimulated emission; the drift of the electrons is thus driven by the cavity photon density. The gain recovery is qualitatively different from that in conventional lasers due to the superlattice transport in the cascade.     

Recent progress in the development of type II interband cascade lasers

Type-II interband cascade lasers combine the advantage of an interband optical transition with interband tunneling to enable the cascading of type-II quantum well active regions as is done in type-I quantum cascade laser. The relatively high radiative efficiency resulting from interband optical transitions translates into very low-threshold current densities, and when combined with the high quantum efficiency of cascade lasers, this diode laser design has the potential to operate under cw conditions at room temperature with high output power. Experimental results have already demonstrated some of this potential including high differential external quantum efficiency (>600%), high peak output power (6 W/facet at 80 K), high cw power conversion efficiency (>17% at 80 K), and operation at 300 K under pulsed conditions. Recent work aimed at reducing device thermal resistance and increasing cw operating temperature is reviewed including the demonstration of significant reductions in thermal resistance (averaging 25 K/W or 40% for 1-mm-long devices), 80 K cw operation at 3.4 μm with high-power conversion efficiency (23%) and high differential external quantum efficiency (532%), and cw operation up to 214 K.     

三势垒隧穿结构中由外加垂直磁场引入的高子带非热占据

在一个特殊设计的三垒双阱异质结构中 ,注入到入射端量子阱中的电子 ,首先经过子带间弛豫填充到较低能级 ,紧接着通过共振隧穿逃逸出后面的双势垒结构 ,流入收集电极 ,完成了整个输运过程。通过比较带间光荧光谱中E2 HH1 与E1 HH1 两峰的强度 ,我们发现外加垂直磁场可以抑制子带间的LO声子和LA声子散射 ,使能量较高的子带上出现了明显的非热平衡占据。这一发现提供了一种新的控制子带间散射速率 (量子级联激光器的主要机制 )的有效方法 ,使得在量子阱子带间实现粒子数反转变得更加容易。     

Super-radiant surface emission from a quasi-cavity hot electron light emitter

The Hot Electron Light Emitting and Lasing in Semiconductor Heterostructure (HELLISH-1) device is a novel surface emitter which utilises hot carrier transport parallel to the layers of a Ga1–xAlxAs p-n junction incorporating a single GaAs quantum well on the n-side of the junction plane. Non-equilibrium electrons are injected into the quantum well via tunnelling from the n-layer. In order to preserve the charge neutrality in the depletion region, the junction undergoes a self-induced internal biasing. As a result the built-in potential on the p-side is reduced and hence the injection of non- equilibrium holes into the quantum well in the active region is enhanced. The work presented here shows that a distributed Bragg reflector grown below the active region of the HELLISH device increases the emitted light intensity by two orders of magnitude and reduces the emission line-width by about a factor of 3 in comparison with the original HELLISH-1 structure. Therefore, the device can be operated as an ultrabright emitter with higher spectral purity.     

Impact ionization and quantum efficiency in semiconductors

This paper presents a general theory of quantum efficiency in semiconductors. A system of equations is derived describing multiple impact ionization (cascade process) due to electrons, or holes, generated by the primary absorption process. Two secondary relaxations processes are considered: interband Auger transitions and emission of phonons. The spectral dependence of quantum efficiency is derived for three special types of the band structure of semiconductors.On leave from the Institute of Solid State Physics, Czechosl. Acad. Sci., Cukrovarnická 10, Praha 6, Czechoslovakia.The writer is greatly indebted to prof. J. Linhard for enabling him to spend a very stimulating time in the Institute of Physics of the University of Aarhus.     

The effects of carrier degeneracy on transport properties of the double heterostructure injection laser

It is shown that carrier degeneracy plays an important role in determining the electrical properties of double heterostructure injection lasers. Correct statistical treatment of the charge cariers in the device leads to a generalised Einstein relation between the carrier transport coefficients. Such a relation (for both electrons and holes) is used in numerical solutions of semiconductor transport equations applicable to the laser. Experimentally observed I–V characteristics of the laser are explained in terms of carrier degeneracy effects.     

Nano-plasmon enhancement effect on MWIR light emitting diode performance

We observed a significant increase in electro luminescence from GaSb based mid-wave infrared (MWIR) LED device through coupling with localized surface plasmon of a single layer Au nano-particles. We fabricated an interband cascade (IC) LED device with nine cascade active/injection layers with InAs/Ga_1−x In_xSb/InAs quantum well (QW) active region. Thin Au plasmon layer of 20 nm thickness is deposited on top anode electrode by e-beam technique, which resulted in 100% increase in light output for 50 μm square mesa device. We also observed a reduction in the device turn on voltage and increase in the apparent black body emission temperature due to nano-structure surface plasmon layer.     

Infrared semiconductor lasers for sensing and diagnostics

There is an increasing demand for spectrally agile compact solid-state lasers for spectroscopic sensing and diagnostics. This demand can be met by III–V semiconductor-based lasers employing various design concepts for the active region. These concepts include, apart from the classical type-I interband diode laser, the type-II W-laser and the unipolar quantum cascade laser. Representative device data will be presented for these three types of lasers in conjunction with a discussion of the relative merits of the different active-region concepts. PACS 42.55.Px; 42.62.Fi; 81.05.Ea; 81.07.St     

Beam properties of injection profiled quantum dot lasers

The impact of injection current profiling on the spatial mode structure of quantum dot semiconductor lasers is investigated. Numerical simulations based on a spatial extension of a simple rate equation model for quantum dot devices reveal the role of non-resonant carries in the appearance of strong dips in the optical field of the device. Symmetry breaking may also occur whereby the position of the dip shifts from the centre of the injection region.