高功率半导体激光器结温与1/f噪声的关系研究

高功率半导体激光器的结温上升, 不仅影响它的输出功率、斜坡效率、阈值电流和寿命, 而且还会产生光谱展宽和波长偏移. 因此, 热管理成为抽运激光器研发中的一个主要问题. 本文首先建立了噪声功率谱与结温变化的物理模型, 根据压缩感知理论, 将测量得到含有高斯白噪声和1/f噪声的混叠复合噪声信号稀疏化后, 进行基追踪算法去噪, 通过改变算法的迭代次数及测量矩阵大小, 获得1/f噪声电压功率谱与结温变化关系曲线, 避免了直接测量结温的复杂性.通过数值估计结果, 可以较好地指导高功率半导体激光器的热管理工作. 关键词： f噪声')" href="#">1/f噪声 结温度 热阻 高功率半导体激光器     

10 W级主控振荡放大半导体激光芯片封装实验研究

结温升高是影响主控振荡放大(MOPA)半导体激光芯片输出功率的重要因素,为解决MOPA芯片的多电极封装和高效散热问题,提出了一种正装和热扩散辅助次热沉相结合的封装结构。建立了该封装结构的3D热模型,对比研究了倒装封装结构、正装无辅助次热沉结构与正装有辅助次热沉结构对MOPA半导体激光器结温的影响。计算结果表明,采用正装有辅助次热沉结构与倒装封装结构散热性能接近,且显著优于正装无辅助次热沉结构,结温降低幅度最高可达40%。另外,采用正装有辅助次热沉封装结构的MOPA半导体激光芯片在连续工作条件下输出功率为10.5 W,谱宽可实现半高全宽小于0.1 nm,中心波长随电流的变化约14 pm/A,实现了10 W级MOPA芯片的封装,验证了该封装结构的有效性。     

C-mount封装激光器热特性分析与热沉结构优化研究

为了降低单管半导体激光器的结温、提高器件的散热效果,基于C-mount热沉的热特性分析提出了一种优化的台阶热沉结构,研究了单管激光器结温和腔面侧向温度分布曲线的影响。在热沉温度298 K和连续输出功率10 W的条件下,腔长为1.5 mm的典型C-mount封装结构激光器的结温为343.6 K,热阻为4.6 K/W。通过在典型C-mount热沉中引入台阶结构,使封装激光器的结温降低为333.8 K,热阻减小到3.5 K/W。计算表明,其输出功率可提高近20%。     

半导体激光器光热光强调制的频率与相位特性

本文在半导体激光器结温变化主要由限制层光热转化引起的情况下,通过求解热传导方程和速率方程得到半导体激光器光热光强调制的频率特性和相位特性.分析表明理论同实验结果相一致.     

采用半导体激光器自身pn结特性测温的 半导体激光器恒温控制

温度对半导体激光器的发射波长有很大的影响,而很多应用都要求半导体激光器的发射波长是稳定的。针对使用测温元件作为温度传感器进行半导体激光器恒温控制中存在的温度误差,提出了以半导体激光器自身pn结作为温度检测元件进行半导体激光器恒温控制的方法,设计了半导体制冷器的驱动电路。该方法利用pn结的温度敏感特性,首先通过实际测量标定pn结的温度与其两端压降的对应关系,然后通过测量压降得出相应的实际温度。实验结果表明,采用该方法消除了使用温度传感器进行半导体激光器恒温控制中温度梯度造成的恒温误差,提高了测量速度,显著减小了超调量,消除了静差和波动。     

管式炉中半导体激光器巴条Au80Sn20焊料封装研究

为了提高半导体激光器的封装质量和效率,引入管式炉利用夹具进行批量封装。由于封装质量的好坏直接影响半导体激光器的输出特性和使用寿命,利用MOCVD生长808 nm芯片,重点分析了管式炉温度和封装时间对半导体激光器巴条双面金锡封装质量的影响。利用X射线检测、结电压、光电特性参数和smile效应测试手段,确定了管式炉封装半导体激光器巴条的最优封装条件,为以后的产业化提供了指导意义。     

基于外腔反馈二极管线阵列的smile效应测量方法

采用外建激光谐振腔,在低于原芯片阈值的电流激励下对LDA的每个发光点进行单独测量,从而分析整个半导体激光阵列(LDA)的smile效应。实验中利用镀膜反射率大于半导体前腔面的外腔镜形成外腔半导体激光器。在外腔中插入曲面平行于p-n结的柱面镜,使只在光轴上的发光点与外腔镜形成外腔激光器,降低该发光点的激光阈值,从而使其在正常的阈值以下的电流激励下输出激光,在平行于p-n结的方向移动柱面镜,可以逐个对半导体激光器中的发光点进行选择测量,从而获得LDA smile效应的测量值。测量中的低电流激励产生的热量对芯片寿命没有影响,对LDA的发光点的单个测量也避免了其他发光点对CCD的影响。     

大功率半导体激光器散热研究综述

近年来,半导体激光器功率不断提高,由之引发的散热问题已成为限制半导体激光器发展的瓶颈。芯片温度升高引起激光器性能下降,要使激光器在大功率条件下依然保持良好特性就必须强化对激光器芯片的散热。通过分析激光器芯片温度对激光器各项性能指标的影响,说明了降低芯片温度对保证激光器正常工作的重要性。鉴于流体侧的对流传热热阻在总热阻起主导作用,重点分析半导体激光器散热结构中流体侧的散热方法,并将其分为传统散热方法和新型散热方法,传统散热方法包括平板热沉散热、大通道水冷等,新型散热方法包括微通道散热、喷雾冷却、射流冲击、热管散热和液态金属散热。总结了各种方法的优缺点,从热流密度和温差两个指标评价各种散热方法,探讨其在激光器散热上的应用前景。     

半导体激光器热弛豫时间测试技术研究

利用脉冲工作状态下半导体激光器激射光谱随结温升高发生红移的原理，用Boxcar扫描在一定波长下的半导体激光器光功率随脉冲时间的变化信号，测得其时间分辨光谱；根据对应的峰值光功率出现时刻随波长变化的曲线，计算得到热弛豫时间参量值.利用此方法对一种半导体激光器进行了测试，得到其热弛豫时间为1.2 ms.     

表面液晶-垂直腔面发射激光器阵列的热特性

液晶与垂直腔面发射半导体激光器(VCSELs)阵列结合可实现波长可调谐、偏振精确控制等,同时液晶的引入也会改变垂直腔面发射半导体激光器阵列的热特性,本文设计了表面液晶-垂直腔面发射激光器阵列结构,并开展了阵列的热特性实验研究.对比分析了向列相液晶层对VCSEL阵列热特性的影响,实验结果表明,1×1,2×2,3×3三种表面液晶-VCSEL阵列的阈值电流温度变化率最高可降低23.6%,热阻降低26.75%;同时,激光器阵列各发光单元之间的温度均匀性显著提高,出光孔与周围温差小于0.5℃.综上所述,VCSEL阵列中液晶层的引入不仅大大加速激光器阵列单元热量扩散,而且降低了有源区结温,提高了VCSELs激光器阵列热特性,为实现高光束质量的单偏振波长可控VCSEL激光器阵列打下了良好的理论和实验基础.     

Sn3.0Ag0.5Cu倒装焊点中的电迁移

采用10⁴ A/cm²数量级的电流密度对Sn30Ag05Cu倒装焊点中的电迁移机理作了研究.电迁移引起的原子（或空位）的迁移以及在此过程中形成的焦耳热,使Sn30Ag05Cu倒装焊点的显微形貌发生变化.电迁移作用下,由于空位的定向迁移和局部的电流聚集效应使阴极芯片端焊料与金属间化合物界面形成薄层状空洞.处于阴极的Cu焊盘的Ni（P）镀层与焊料间也产生了连续性空洞,但空洞面积明显小于处于阴极的芯片端焊料与金属间化合物界面.焊盘中的Cu原子在电迁移作用下形成与电子流方向一致的通量,最终导致焊点高电流密度区域出现连续性的金属间化合物且金属间化合物量由阴极向阳极逐渐增多. 关键词： Sn30Ag05Cu 倒装 焊点 电迁移     

High-resolution X-ray imaging—a powerful nondestructive technique for applications in semiconductor industry

The availability of high-brilliance X-ray sources, high-precision X-ray focusing optics and very efficient CCD area detectors has contributed essentially to the development of transmission X-ray microscopy (TXM) and X-ray computed tomography (XCT) with sub-50 nm resolution. Particularly, the fabrication of high aspect ratio Fresnel zone plates with zone widths approaching 15 nm has contributed to the enormous improvement in spatial resolution during the previous years. Currently, Fresnel zone plates give the ability to reach spatial resolutions of 15 to 20 nm in the soft and of about 30 to 50 nm in the hard X-ray energy range. X-ray microscopes with rotating anode X-ray sources that can be installed in an analytical lab next to a semiconductor fab have been developed recently. These unique TXM/XCT systems provide an important new capability of nondestructive 3D imaging of internal circuit structures without destructive sample preparation such as cross sectioning. These lab systems can be used for failure localization in micro- and nanoelectronic structures and devices, e.g., to visualize voids and residuals in on-chip metal interconnects without physical modification of the chip. Synchrotron radiation experiments have been used to study new processes and materials that have to be introduced into the semiconductor industry. The potential of TXM using synchrotron radiation in the soft X-ray energy range is shown for the nondestructive in situ imaging of void evolution in embedded on-chip copper interconnect structures during electromigration and for the imaging of different types of insulating thin films between the on-chip interconnects (spectromicroscopy).     

Annealing behavior of a void network in amorphous silicon

A void network in a-Si films prepared by vacuum deposition was studied. A close relationship in annealing behavior has been observed between the changes in surface area of voids and in the ESR signal strength.     

High-power quantum well remote junction laser and its electrical noise characteristics

We designed and fabricated new structure lasers, the high-power AlGaAs/GaAs remote junction (RJ) single quantum well (SQW) semiconductor lasers whose p–n junction was separated from the active layer. The RJ lasers showed marked reduction of threshold current during early aging period. This reduction was accompanied by a decrease of non-radiative recombination centers in the active layer. For the RJ SQW lasers, the relation between the low-frequency electrical noise and the lifetime of devices is different from the conventional SQW lasers.     

Void effect on mechanical properties of copper nanosheets under biaxial tension by molecular dynamics method

The relationship between void size/location and mechanical behavior under biaxial loading of copper nanosheets containing voids are investigated by molecular dynamics method. The void location and the void radius on the model are discussed in the paper. The main reason of break is discovered by the congruent relationship between the shear stress and its dislocations. Dislocations are nucleated at the corner of system and approached to the center of void with increased deformation. Here, a higher stress is required to fail the voided sheets when smaller voids are utilized. The void radius influences the time of destruction. The larger the void radius is, the lower the shear stress and the earlier the model breaks. The void location impacts the dislocation distribution.     

Surface morphological response of crystalline solids to mechanical stresses and electric fields

Surface morphological evolution under the action of external fields is a fascinating topic that has attracted considerable attention within the surface science community over the past two decades. In addition to the interest in a fundamental understanding of field-induced nonlinear response and stability of surface morphology, the problem has been technologically significant in various engineering applications such as microelectronics and nanofabrication. In this report, we review theoretical progress in modeling the surface morphological response of stressed elastic solids under conditions that promote surface diffusion and of electrically conducting solids under surface electromigration conditions. A self-consistent model of surface transport and morphological evolution is presented that has provided the basis for the theoretical and computational work that is reviewed. According to this model, the surface morphological response of electrically conducting elastic solids to the simultaneous action of mechanical stresses and electric fields is analyzed. Emphasis is placed on metallic surfaces, including surfaces of voids in metallic thin films.Surfaces of stressed elastic solids are known to undergo morphological instabilities, such as the Asaro–Tiller or Grinfeld (ATG) instability that leads to emanation of crack-like features from the surface and their fast propagation into the bulk of the solid material. This instability is analyzed theoretically, simulated numerically, and compared with experimental measurements. The surface morphological evolution of electrically conducting, single-crystalline, stressed elastic solids under surface electromigration conditions is also examined. We demonstrate that, through surface electromigration, a properly applied and sufficiently strong electric field can stabilize the surface morphology of the stressed solid against both crack-like ATG instabilities and newly discovered secondary rippling instabilities; the effects of important parameters, such as surface crystallographic orientation, on the surface morphological response to the simultaneous action of an electric field and mechanical stress also are reviewed. In addition, electromigration-driven surface morphological response is analyzed systematically, focusing on the current-driven surface morphological evolution of voids in metallic thin films; this analysis has been motivated largely by the crucial role of void dynamics in determining the reliability of metallic interconnects in integrated circuits and has led to the interpretation of a large body of experimental observations and measurements. The electromigration-driven translational motion of morphologically stable voids, effects of current-driven void dynamics on the evolution of the electrical resistance of metallic thin films, and current-driven void–void interactions also are reviewed. Furthermore, theoretical studies are reviewed that demonstrated very interesting current-driven nonlinear void dynamics in stressed metallic thin films, including the inhibition of electromigration-induced instabilities due to the action of biaxial tensile stress, and stress effects on the electromigration-driven translational motion of morphologically stable voids.Complex, oscillatory surface states under surface electromigration conditions have been observed in numerical studies. In this report, emphasis is placed on void surfaces in metallic thin films, for which stable time-periodic states have been demonstrated. It is shown that increasing parameters such as the electric-field strength or the void size past certain critical values leads to morphological transitions from steady to time-periodic states; the latter states are characterized by wave propagation on the surface of a void that migrates along the metallic film at constant speed. The transition onset corresponds to a Hopf bifurcation that may be either supercritical or subcritical, depending on the symmetry of the surface diffusional anisotropy as determined by the crystallographic orientation of the film plane. It is also shown that, in the case where the Hopf bifurcation is subcritical, the simultaneous action of mechanical stress leads the current-driven void morphological response to the stabilization of chaotic attractors; in such cases, as the applied stress level increases, the void dynamics is set on a route to chaos through a sequence of period-doubling bifurcations. The observation of current-driven chaotic dynamics in homoepitaxial islands also is discussed.     

The junction voltage saturation and reliability of semiconductor lasers

This paper reports theoretical and experimental work on the dependence of semi-conductor laser operation on junction voltage saturation. The relation between junction voltage saturation and the reliability of semiconductor lasers is discussed.     

Crystal forms of hillocks and voids formed by electromigration on ultrapure gold and silver wires

Hillocks and voids (vacancy crystals) which were formed by electromigration on ultrapure gold and silver wires, showed only the combined crystal forms {111} and {100}. These planes are identical with the equilibrium planes G_I, calculated by Stranski and Kaishew for nonpolar substances under the assumption of only nearest neighbor interaction. Hillock and void nucleation occurred on crystal imperfections (heterogeneous nucleation). Hillocks and vacancy crystals (voids) on gold showed twin formation obeying the spinel law. Dedicated to Professor I. N. Stranski on the occasion of his 80th birthday.