AlAs选择性湿氮氧化的工艺条件对氧化速率的影响

结合垂直腔面发射激光器的制备,详细研究了AlAs选择性湿氮氧化工艺中氧化炉温、氮气流量、水温等条件和AlAs薄层的横向氧化速率之间的关系及其对氧化结果的影响,给出了合理的定性解释,并得到了可精确控制氧化过程及其均匀性的工艺条件.在优化的工艺条件下运用湿氮氧化制备出低阈值的InGaAs垂直腔面发射激光器.     

980nm垂直腔面发射激光器的研制

采用低压金属有机化合物气相外延生长技术,应用AlAs/AlGaAs选择性湿氮氧化工艺实现光、电限制,制备出具有一定性能的980nm内腔接触式氧化物限制型顶发射980nm垂直腔面发射激光器(VCSEL).通过制备不同氧化孔径尺寸的VCSEL,分析了氧化孔径尺寸大小对器件的阈值电流和串联电阻的影响.获得的最小阈值电流为0.8mA,最大光输出功率达8mW.     

980nm垂直腔面发射激光器的研制

采用低压金属有机化合物气相外延生长技术,应用AlAs/AlGaAs选择性湿氮氧化工艺实现光、电限制,制备出具有一定性能的980nm内腔接触式氧化物限制型顶发射980nm垂直腔面发射激光器(VCSEL).通过制备不同氧化孔径尺寸的VCSEL,分析了氧化孔径尺寸大小对器件的阈值电流和串联电阻的影响.获得的最小阈值电流为0.8mA,最大光输出功率达8mW.     

980nm垂直腔面发射激光器的研制

采用低压金属有机化合物气相外延生长技术,应用AlAs/AlGaAs选择性湿氮氧化工艺实现光、电限制，制备出具有一定性能的980nm内腔接触式氧化物限制型顶发射980nm垂直腔面发射激光器(VCSEL). 通过制备不同氧化孔径尺寸的VCSEL，分析了氧化孔径尺寸大小对器件的阈值电流和串联电阻的影响. 获得的最小阈值电流为0.8mA，最大光输出功率达8mW.     

垂直腔面发射激光器中选择性氧化工艺稳定性研究

选择性氧化工艺已经成为制备高性能垂直腔面发射激光器(VCSEL)的关键技术,氧化后形成的氧化层提供了良好的电限制和折射率导引,但选择性氧化速率是呈线性规律还是抛物线规律仍存在很大的争议.在多种温度条件下,做了环形沟槽和环形分布孔的氧化实验,这是在垂直腔面发射激光器中采用的两种结构.实验结果表明,氧化窗口形状对氧化速率的影响也依赖温度条件,并对这种实验现象给出了定性解释.     

高铝AlxGa1-xAs氧化层对垂直腔面发射激光器的影响

针对可见光垂直腔面发射激光器的制备,通过湿氮氧化实验和测量微区光致发光谱分别研究了高铝组分AlxGa1-xAs的氧化特性及氧化产物的收缩应力对有源区的影响,结合器件结构设计确定了氧化限制层AlxGa1-x-As的铝组分和最佳位置,并制备出了低阈值电流的AlGaInP系垂直腔面发射激光器.     

光子晶体垂直腔型表面发射和接收光电子器件

介绍了制作光子晶体垂直腔面发射激光器实验研究的主要内容,包括材料的光谱测试分析、氧化工艺以及制作光子晶体等,成功制作了波长在980nm附近的光子晶体垂直腔面发射激光器.在此基础上,采用高精度湿法腐蚀和感应耦合等离子体干法刻蚀技术,研究制作了基于垂直腔面发射激光器外延材料的光子晶体谐振腔增强型探测器.     

AlAs/AlGaAs的湿氧氧化及其在VCSEL制备中的应用

根据制备垂直腔面发射激光器 (VCSEL)电流限制层的需要 ,通过实验方法研究了氧化温度、Al组分和晶向等条件对AlGaAs氧化速率的影响 ,得到适用于VCSEL的材料参数和氧化条件 ;对氧化后表面分层、欧姆接触特性变差等现象进行分析 ,得到解决或改善方案。比较AlAs和Al0 .98Ga0 .0 2 As氧化特性及氧化后的热稳定性 ,结果表明Al0 .98Ga0 .0 2 As较AlAs更适于作VCSEL电流限制层。将优化的氧化条件及材料参数应用于VCSEL制备 ,得到室温连续工作的VCSEL器件 ,其阈值电流为 0 .8mA ,激射波长为 980nm ,工作电流为 15mA时输出功率可达 3.2mW。     

光子晶体垂直腔型表面发射和接收光电子器件

介绍了制作光子晶体垂直腔面发射激光器实验研究的主要内容,包括材料的光谱测试分析、氧化工艺以及制作光子晶体等,成功制作了波长在980nm附近的光子晶体垂直腔面发射激光器.在此基础上,采用高精度湿法腐蚀和感应耦合等离子体干法刻蚀技术,研究制作了基于垂直腔面发射激光器外延材料的光子晶体谐振腔增强型探测器.     

微小孔阵列垂直腔面发射激光器的研究

在980nm波长的大功率垂直腔面发射激光器(VCSEL)的基础上制备了高输出功率的微小孔阵列半导体激光器,其最大输出光功率达到了1mW。介绍了针对微小孔阵垂直腔面发射激光器的特殊制备工艺,并对其特性进行了分析。     

Temperature and thickness dependence of steam oxidation of AlAs incylindrical mesa structures

The Deal-Grove model of thermal oxidation kinetics is adapted to cylindrically symmetric mesa structures and applied to study steam oxidation of AlAs. Oxidation process parameters are extracted from available experimental data as functions of temperature and the AlAs layer thickness. The oxidation rate is found to be very sensitive not only to temperature, but also to the oxidation front position inside the mesa. The oxidation rate slows down as the oxidation front moves into the mesa, reaches a minimum, and then accelerates at the final stages of the oxidation process. Complex nonmonotonic dependence of the oxidation process on layer thickness is also revealed     

Wet Oxidation in a Square Sandwich Composite of GaAs/AlAs/GaAs

Wet oxidation in a square sandwich composite, GaAs/AlAs/GaAs, with varying thickness of the AlAs layer was investigated in a temperature range of 400°C–480°C. At a given temperature and time, the oxidation depth increases with increasing thickness of the AlAs layer. A model based on the boundary layer diffusion in a sandwich composite is used to interpret the thickness effect, and the theoretical predictions are in good agreement with the measured oxidation data. The theory also predicts a value of 0.53 eV ± 0.03 eV to be the difference in activation energies of water vapor diffusion in the central layer AlAs and the outer layers GaAs in the temperature range studied. Such a difference remains to be verified experimentally.     

AlAs氧化层的Raman研究

利用 Nomarski光学显微镜和 Raman光谱仪对分子束外延生长的 Al As层热氧化进行了系统的研究。对未氧化 ,氧化及氧化加原位退火的样品分析表明 ,目前氧化热稳定性差的主要因素是随氧化进行而产生的可挥发性产物如 As、As2 O3在氧化层中的残留量。在此分析的基础上 ,优化了氧化条件 ,使 Al As氧化的热稳定性有了质的提高 ,可以经受较高温度的退火 ,并消除了氧化层与两边 Ga As层之间的崩裂现象     

AlAs oxidation process in GaAs/AlGaAs/AlAs heterostructures grown by molecular beam epitaxy on GaAs (n11)A substrates

The lateral oxidation of AlAs layers grown on GaAs (100), (110) and (n11)A-oriented substrates (n=1, 2, 3, 4) was studied. The temperature dependence of the oxidation rate was measured between 390°C and 450°C. The oxidation rate is highly anisotropic and the anisotropy is related to the symmetry of the crystal structure. The oxidation process has an activation energy that depends on substrate orientation. The oxidation front line becomes irregular for temperatures higher than 450°C and the surface of the samples was degraded when the temperature exceeded 540°C. The time dependence of the oxidation rate was found to be similar to the Si oxidation process.     

Increased lateral oxidation rates of AllnAs on InP using short-period superlattices

We present greatly increased lateral oxidation rates for AlInAs grown as a short-period superlattice of InAs and AlAs compared to the analog alloy. The tensile strain in the AlAs layers is balanced by the compressive strain in the InAs layers, creating a strain-compensated alloy lattice-matched to InP. Oxidation layers with superlattice periods up to 40 Å and cladded by lattice-matched InGaAs layers were grown on InP substrates and laterally oxidized at temperatures ranging from 450°C to 525°C. The oxidation depth for a given time and temperature was seen to increase with superlattice period, allowing increased oxidation depths or reduced oxidation temperatures compared to the analog alloy. Oxidized layers were examined with transmission electron microscopy and were found to retain some of the superlattice structure.     

Lasing characteristics of high-performance narrow-stripe InGaAs-GaAs quantum-well lasers confined by AlAs native oxide

High-performance narrow-stripe InGaAs-GaAs quantum-well lasers with integral buried AlAs native-oxide layers have been fabricated. AlAs native-oxide layers above and below waveguide region were employed for current and optical confinement to form narrow-stripe lasers. A low temperature (400/spl deg/C) anisotropic wet oxidation technique was used to selectively oxidize AlAs layers in the epitaxial structure. The devices demonstrated continuous wave threshold currents of 3.5 mA, external quantum efficiencies of 82%, and a characteristic temperature of 133 K for 1.8 /spl mu/m-wide aperture, 400 /spl mu/m-long devices. Threshold currents of 1.7 mA were obtained by applying HR/HR coatings.     

Strain relaxation in InGaAs lattice engineered substrates

Strain relaxation of hypercritical thickness In_xGa_1−xAs layers has been observed during lateral oxidation of underlying AlAs layers. Strain relaxation of In_xGa_1−xAs layers was studied as a function of indium composition and the AlAs oxidation temperature. It is proposed that the enhanced strain relaxation is due to two factors. The first is enhanced motion of threading dislocations due to stresses generated during the lateral oxidation process. The second is the porous nature of the In_xGa_1−xAs/Al₂O₃ interface that minimizes the interaction of threading dislocations with existing misfit dislocation segments. The extent of strain relaxation increases with increasing oxidation temperature, whereas the efficiency of strain relaxation was found to decrease with increasing indium composition. The efficiency of strain relaxation upon oxidation can be improved by reducing the misfit dislocation density at the In_xGa_1−xAs/AlAs interface prior to oxidation and by changing the nature of the In_xGa_1−xAs/Al₂O₃ interface.     

In situ optical monitoring of AlAs wet oxidation using a novellow-temperature low-pressure steam furnace design

To reproducibly define small features by oxidizing AlGaAs layers, it is essential to have good control over the oxidation reaction. We have integrated a glass viewport into a low-pressure (5 torr) cold-walled oxidation chamber to enable in situ optical monitoring of the sample during oxidation. To gain additional control, we reduced the oxidation temperature to 325°C, consequently slowing the oxidation rate to 2 μm/h. Real-time in situ optical measurements of AlAs oxidation rates were performed using this system and the results were compared with a standard model. Oxide-semiconductor distributed Bragg reflectors (DBR's) were also fabricated and measured, yielding highly reflective mirrors suitable for vertical cavity surface-emitting laser (VCSEL) fabrication     

RHEED振荡精确测量AlGaAs生长速率研究

采用分子束外延技术,在GaAs衬底上生长GaAs,AlAs和AlGaAs时,实现RHEED图像和RHEED强度振荡的实时监测已被证明是一种有效工具。通过RHEED可讨论GaAs表面结构和生长机制,并可以估算衬底温度,更重要的是能计算出材料的生长速率。RHEED强度振荡周期决定生长速率,每一个周期对应一个单层。实验测量GaAs的生长周期为0.82s,每秒沉积1.22单分子层,AlAs的生长周期为2.35s,每秒沉积0.43单分子层。     

Molecular-beam epitaxy of InGaAs/InAlAs/AlAs structures for heterobarrier varactors

The molecular-beam epitaxy of InGaAs/InAlAs/AlAs structures for heterobarrier varactors is studied and optimized. The choice of the substrate-holder temperature, growth rate and III/V ratio in the synthesis of individual heterostructure regions, the thickness of AlAs inserts and barrier-layer quality are critical parameters to achieve the optimal characteristics of heterobarrier varactors. The proposed triple-barrier structures of heterobarrier varactors with thin InGaAs strained layers immediately adjacent to an InAlAs/AlAs/InAlAs heterobarrier, mismatched with respect to the InP lattice constant at an AlAs insert thickness of 2.5 nm, provides a leakage current density at the level of the best values for heterobarrier varactor structures with 12 barriers and an insert thickness of 3 nm.