大应变In0.3Ga0.7As/GaAs量子阱激光器的生长和研究

金属有机物化学气相沉积(MOCVD)方法生长应变InGaAs／GaAs量子阱，应变缓冲层结合生长中断改善量子阱的PL谱特性．用该量子阱制备的激光器有很低的阈值电流密度(43A／cm^2)和较高的斜率效率(0．34W／A，per facet)．     

MOCVD生长1．06μm InGaAs／GaAs量子阱LDs

用低压MOCVD生长应变InGaAs/GaAs量子阱,采用中断生长、应变缓冲层(SBL)、改变生长速度和调节Ⅴ/Ⅲ等方法改善InGaAs/GaAs量子阱的光致发光(PL)质量。PL结果表明,10s生长中断结合适当的SBL生长的量子阱PL谱较好。该量子阱应用于1.06μm激光器的制备,未镀膜的宽条激光器(100μm×1000μm)有低阈值电流密度(110A/cm2)和高的斜率效率(0.256W/A,per.facet)。     

用MOCVD方法生长940nm应变多量子阱发光二极管

采用金属有机物化学气相淀积（MOCVD）方法设计并生长了应变多量子阱InGaAs/AlGaAs,并且对其进行了光致发光（PL）谱、双晶X射线衍射（DXRD）谱和电化学C－V等的测试。然后以InGaAs/AlGaAs作为有源层，以GaAs衬底作为透明衬底，p面金属电极AuBe合金作为镜面反射层，采用倒装技术制备了近红外发光二极管（LED）。在输入电流为20mA下的正向电压为1．2V左右，电致发光谱的峰值波长为938nm,10μA下的反向击穿电压为5－6V，在输入电流为50mA下得出输出功率3．5mW，对应电压为1．3V,在输入电流为300mA时得到最大输出功率为12mW。     

应变InGaAs/GaAs量子阱MOCVD生长优化及其在980 nm半导体激光器中的应用

使用低压MOCVD生长应变InGaAs/GaAs 980 nm量子阱.研究了生长温度、生长速度对量子阱光致发光谱(PL)的影响.并将优化后的量子阱生长条件应用于980 nm半导体激光器的研制中,获得了直流工作下,阈值电流为19 mA,未镀膜斜率效率为0.6 W/A,输出功率在100 mW的器件.     

MOCVD生长Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱的结构和光学特性

采用金属有机物化学气相淀积(MOCVD)技术,在蓝宝石衬底上生长了Al0.48Ga0.52N/Al0.54Ga0.36N多量子阱(MQWs)结构。通过双晶X射线衍射(DCXRD)、原子力显微镜(AFM)和阴极荧光(CL)等测试技术,分别对样品的结构和光学特性进行了表征。在DCXRD图谱中,可以观察到明显的MQWs衍射卫星峰,通过拟和,MQWs结构中阱和垒的厚度分别为2.1和9.4nm,Al组分分别为0.48和0.54。在AFM表面形貌图上,可以观察到清晰的台阶流,表明MQWs获得了二维生长;与此同时,MQWs结构存在一些裂缝,主要原因为AlGaNMQWs结构和下层GaN层间存在很大的应力。CL测试表明,AlGaNMQWs结构的发光波长为295nm,处于深紫外波段,同时观察到处于蓝光、绿光波段的缺陷发光。     

应变层多量子阱InGaAs—GaAs的光电流谱研究

在10—300K温度范围,用光电流谱方法研究了未掺杂的x为0.1、0.15和0.2,InGaAs层厚度为8和15nm的In_xGa_(1-x)As—GaAs应变层多量子阱的能带结构。在1.240—1.550eV光子能量范围,除11H、11L和22H激子跃迁以及GaAs的基本带间跃迁外,还观察到束缚子带到连续带的跃迁。对样品In_(0.15)Ga_(0.85)As(8nm)-GaAs(15nm),观察到11H重空穴激子的2s及其它激发态跃迁,由此得到激子结合能的近似值,约为8meV。重空穴能带台阶Q_v=0.40±0.02。应变效应使得电子和重空穴束缚在InGaAs层,而轻空穴束缚在GaAs层。     

MOCVD生长GaAs/AlGaAs量子阱研究

利用常压MOCVD技术在较低生长速率下生长出多种GaAs/AlGaAs多量子阱结构材料,利用低温PL谱和TEM对材料结构进行了表征。所得势阱和势垒结构厚度均匀平整,最窄阱宽为1.8nm。本研究表明,低速率(γ≤0.5nm/s)连续生长工艺能够避免杂质在界面富集,优于间断生长工艺,且在掺si n~+-GaAs衬底上所得量子阱发光强度高于掺Cr SI-GaAs衬底上的结果。     

生长停顿改善MOCVD生长InGaN/GaN多量子阱的特性

利用金属有机物化学气相淀积(MOCVD)生长了InGaN/GaN多量子阱(MQWs)结构,研究了生长停顿对InGaN/GaN MQWs特性的影响.结果表明,采用生长停顿,可以改善MQWs界面质量,提高MQWs的光致发光(PL)与电致发光(EL)强度;但生长停顿的时间过长,阱的厚度会变薄,界面质量变差,不仅In组分变低,富In的发光中心减少,而且会引入杂质,致使EL强度下降.     

MBE生长InGaAs／GaAs应变层单量子阱激光器结构材料的研究

采用ＶａｒｉａｎＧｅｎⅡＭＢＥ生长系统研究了ＩｎＧａＡｓ／ＧａＡｓ应变层单量子阶（ＳＳＱＷ）激光器结构材料。通过ＭＢＥ生长实验，探索了Ｉｎ＿ｘＧａ＿（１－ｘ）ｔＡｓ／ＧａＡｓＳＳＱＷ激光器发射波长（λ）与Ｉｎ组分（ｘ）和阱宽（Ｌ＿ｚ）的关系，并与理论计算作了比较，两者符合得很好。还研究了材料生长参数对器件性能的影响，主要包括：Ⅴ／Ⅲ束流比，量子阱结构的生长温度Ｔ＿ｇ（ＱＷ），生长速率和掺杂浓度对激光器波长、阈值电流密度、微分量子效率和器件串联电阻的影响。以此为基础，通过优化器件结构和ＭＢＥ生长条件，获得了性能优异的Ｉｎ＿（０．２）Ｇａ＿（０．８）Ａｓ／ＧａＡｓ应变层单量子阱激光器：其次长为９６３ｎｍ，阈值电流密度为１３５Ａ／ｃｍ￣２，微分量子效率为３５．１％。     

Role of GaAs bounding layers in improving OMVPE growth and performance of strained-layer inGaAs/AIGaAs quantum-well diode lasers

In the growth of organometallic vapor phase epitaxy of InGaAs/AIGaAs single-quan-tum-well heterostructures for strained-layer diode lasers, the growth temperature is 100 to 200° C lower for the InGaAs quantum-well layer than for the AlGaAs cladding layers. Earlier studies showed that laser performance is greatly improved by sandwiching the InGaAs layer between lower and upper GaAs bounding layers that are grown during the times before and after InGaAs growth when the substrate temperature is decreased and increased, respectively. In this investigation, it has been found that laser performance is influenced mainly by the upper bounding layer rather than the lower one. By using Auger analysis in combination with Ar-ion sputtering to determine the composition depth profile of In_0.2Ga_0.8As/GaAs test structures layer without AlGaAs layers, it has been shown that the role of the upper bounding layer is to prevent the evaporation of In from the InGaAs quantum-well layer during the interval before the deposition of the upper AlGaAs cladding layer.     

Ion beam mixing characteristics of MOCVD grown InGaAs/GaAs superlattices

The ion beam mixing behavior of InGaAs/GaAs strained layer superlattice structures grown by metalorganic chemical vapor deposition was studied using secondary ion mass spectroscopy and Rutherford backscattering channeling. The fluence dependence of intermixing by MeV Kr⁺ irradiation has been investigated. Significant intermixing occurs for fluences much lower than for similar intermixing in other superlattice systems (i.e. ALAs/GaAs). The intermixing exhibits no temperature dependence for fluences of 2 x 10¹⁵ to 5 x 10¹⁵ cm⁻² which sharply contrasts with the behavior of the AlAs/GaAs superlattice system which shows a strong temperature dependence, including a miscibility gap, in the temperature range 523 to 973K. Samples irradiated at 573K retain a high degree of crystallinity when compared to lower temperature irradiations indicating that the InGaAs/GaAs superlattice can be disordered and still retain crystallinity.     

Surface photoabsorption monitoring of the growth of GaAs and InGaAs at 650°C by MOCVD

By monitoring the cyclic behavior of surface photoabsorption (SPA) reflectance changes during the growth of GaAs at 650°C and with sufficient H₂ purging time between the supply of trimethylgallium and AsH₃, we have been able to achieve controlled growth of GaAs down to a monolayer. Our results show, as confirmed by photoluminescence (PL) measurements, the possibility of growing highly accurate quantum well heterostructures by metalorganic chemical vapor deposition at conventional growth temperatures. We also present our PL measurements on the InGaAs single quantum wells grown at this temperature by monitoring the SPA signal.     

Critical thickness of GaAs/InGaAs and AlGaAs/GaAsP strained quantum wells grown by organometallic chemical vapor deposition

In this paper we describe a study of strained quantum wells (QWs) as a means to experimentally observe the critical thickness (h _c) for the formation of interfacial misfit dislocations. Two material systems were investigated: GaAs/In_0.11Ga_0.89As, in which the QW layers are under biaxialcompression, and Al_0.35Ga_0.65As/GaAs_0.82P_0.18, in which the QW layers are under biaxialtension. Samples were grown by atmospheric pressure organometallic chemical vapor deposition, and characterized by low-temperature photoluminescence (PL), x-ray diffraction, optical microscopy, and Hall measurements. For both material systems, the observed onset of dislocation formation agrees well with the force-balance model assuming a double-kink mechanism. However, overall results indicate that the relaxation is inhomogeneous. Annealing at 800–850° C had no significant effect on the PL spectra, signifying that even layers that have exceededh _c and have undergone partial relaxation are thermodynamically stable against further dislocation propagation.     

A1.3 μm strained quantum well laser on a graded InGaAs buffer with a GaAs substrate

We grew a 1.3 μm strained-layer quantum well (SL-QW) laser with InGaP cladding layers on a lattice-relaxation buffer layer by metalorganic vapor phase epitaxy. For the lattice-relaxation buffer, we used a compositionally graded InGaAs/GaAs structure. The significantly reduced surface roughness of the InGaP cladding layers achieved by supplying a large amount of H₂Se enables CW operation of our 1.3 μm SL-QW laser. We achieved a low threshold current of less than 10 mA and a high characteristic temperature of 100K around room temperature.     

大应变InGaAs/GaAs/AlGaAs微带超晶格中波红外QWIP的MOCVD生长

基于中波红外(峰值响应波长4.5μm)量子阱红外探测器QWIP进行了大应变In0.34Ga0.66As/GaAs/Al0.35Ga0.65As微带超晶格结构的MOCVD外延生长研究。通过对生长温度、生长速率、Ⅴ/Ⅲ比以及界面生长中断时间等生长参数的系统优化,获得了高质量的外延材料。     

Wavelength tuning in strained layer InGaAs-GaAs-AlGaAs quantum well lasers by selective-area MOCVD

Selective-area growth and regrowth using conventional atmospheric pressure metalorganic chemical vapor deposition is investigated for wavelength tuning in strained layer In_xGa_1-xAsGaAs-Al_y Ga_1-yAs quantum well lasers. Growth inhibition from a silicon dioxide mask is the mechanism used for the selective-area growth rate enhancement. By varying the width of the oxide stripe opening, differences in the growth rate yield different quantum well thicknesses, and hence different lasing wavelengths for devices on the same wafer. Both two-and three-step growth processes are utilized for selective-area epitaxy of strained layer In_xGa_1-xAs-GaAs quantum well active regions, with lasers successfully fabricated from the three-step growth. Scanning electron microscopy and transmission electron microscopy indicate that the absence of an oxide mask during Al_yGa_1-yAs growth is essential for successful device operation. A wide wavelength tuning range of over 630Å is achieved for lasers grown on the same substrate.     

InGaAs/InP材料的MOCVD生长研究

研究了InGaAs/InP材料的MOCVD生长技术和材料的性能特征。InP衬底的晶向偏角能够明显影响外延生长模型以及外延层的表面形貌,用原子力显微镜(AFM)观察到了外延层表面原子台阶的聚集现象(step-bunching现象),通过晶体表面的原子台阶密度和二维生长模型解释了台阶聚集现象的形成。对外延材料进行化学腐蚀,通过双晶X射线衍射(DCXRD)分析发现异质结界面存在应力,用异质结界面岛状InAs富集解释了应力的产生。通过严格控制InGaAs材料的晶格匹配,并优化MOCVD外延生长工艺,制备出厚层InGaAs外延材料,获得了低于1×1015cm-3的背景载流子浓度和良好的晶体质量。