p型掺杂1.3μm InAs/GaAs量子点激光器的最大模式增益特性的研究

对p型掺杂13 μm InAs/GaAs量子点激光器的最大模式增益进行了实验和理论分析.实验上,测量了不同腔长激光器阈值电流密度与总损耗的对应关系,拟合出的最大模式增益为175 cm^-1,与相同结构非掺杂量子点激光器的最大模式增益一致.同时理论分析表明,p型掺杂对InAs/GaAs量子点激光器的最大模式增益并无影响,并且最大模式增益的计算结果与实验值相符.具有较小高度或高宽比的量子点能达到更高的最大模式增益,而较高的最大模式增益对p型掺杂13 μm InAs/GaAs自组织量子点激光器在光通信系统中的应用具有重要意义. 关键词： 最大模式增益 p型掺杂 InAs/GaAs量子点激光器     

Optical properties of 1.3-μm InAs/GaAs quantum dots grown by metal organic chemical vapor deposition

The optical properties of self-assembled InAs quantum dots （QDs） on GaAs substrate grown by metalorganic chemical vapor deposition （MOCVD） are reported. Photoluminescence （PL） measurements prove the good optical quality of InAs QDs, which axe achieved using lower growth temperature and higher InAs coverage. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum （FWHM） are 1305 nm and 30 meV, respectively, which are obtained as the QDs are finally capped with 5-nm In0.06Ga0.94As strain-reducing layer （SRL）. The PL spectra exhibit two emission peaks at 1305 and 1198 nm, which correspond to the ground state （GS） and the excited state （ES） of the QDs, respectively.     

InAs/GaAs量子点1.3 μm单光子发射特性

采用双层耦合量子点的分子束外延生长技术生长了InAs/GaAs量子点样品,把量子点的发光波长成功地拓展到1.3 μm.采用光刻的工艺制备了直径为3 μm的柱状微腔,提高了量子点荧光的提取效率.在低温5 K下,测量得到量子点激子的荧光寿命约为1 ns;单量子点荧光二阶关联函数为0.015,显示单量子点荧光具有非常好的单光子特性;利用迈克耳孙干涉装置测量得到单光子的相干时间为22 ps,对应的谱线半高全宽度为30 μeV,且荧光谱线的线型为非均匀展宽的高斯线型.     

High-performance InAs/GaAs quantum dot laser with dot layers grown at 425℃

We investigate InAs/GaAs quantum dot(QD) lasers grown by gas source molecular beam epitaxy with different growth temperatures for InAs dot layers.The same laser structures are grown,but the growth temperatures of InAs dot layers are set as 425 and 500 ℃,respectively.Ridge waveguide laser diodes are fabricated,and the characteristics of the QD lasers are systematically studied.The laser diodes with QDs grown at 425℃ show better performance,such as threshold current density,output power,internal quantum efficiency,and characteristic temperature,than those with QDs grown at 500 C.This finding is ascribed to the higher QD density and more uniform size distribution of QDs achieved at 425℃.     

A 10Gb/s Directly-Modulated 1.3μm InAs/GaAs Quantum-Dot Laser

We demonstrate 10 Gb/s directly-modulated 1.3 μm InAs quantum-dot （QD） lasers grown on GaAs substrates by molecular beam epitaxy. The active region of the QD lasers consists of five-stacked InAs QD layers. Ridge-waveguide lasers with a ridge width of 4 μm and a cavity length of 600 μm are fabricated with standard lithography and wet etching techniques. It is found that the lasers emit at 1293 nm with a very low threshold current of 5 mA at room temperature. Furthermore, clear eye-opening patterns under 10 Gb/s modulation rate at temperatures of up to 50oC are achieved by the QD lasers. The results presented here have important implications for realizing low-cost, low-power-consumption, and high-speed light sources for next-generation communication systems.     

Mn离子注入InAs/GaAs量子点结构材料的光电性质研究

用高能离子注入(160keV)的方法对InAs/GaAs量子点结构进行掺杂，研究了不同退火工艺处理后量子点的光致发光和电学性能.相对于长时间退火，快速退火处理后的量子点发光通常较强.在相同的退火条件下，量子点发光峰位随着Mn注入剂量的增加，先是往高能量端快速移动，而后发光峰又往低能方向移动.后者可能是由于Mn原子进入InAs量子点，释放了InAs量子点中的应变所致.对于高注入剂量样品和长时间退火样品，变温电阻曲线在40 K附近会出现反常行为. 关键词： 离子注入 InAs/GaAs量子点 光致发光 团簇     

High Characteristic Temperature 1.3μm InAs/GaAs Quantum-Dot Lasers Grown by Molecular Beam Epitaxy

We report the molecular beam epitaxy growth of 1.3 μm InAs/GaAs quantum-dot （QD） lasers with high characteristic temperature T0. The active region of the lasers consists of five-layer InAs QDs with p-type modulation doping. Devices with a stripe width of 4 μm and a cavity length of 1200 μm are fabricated and tested in the pulsed regime under different temperatures. It is found that T0 of the QD lasers is as high as 532 K in the temperature range from 10°C to 60°C. In addition, the aging test for the lasers under continuous wave operation at 100°C for 72 h shows almost no degradation, indicating the high crystal quality of the devices.     

A digital-alloy AlGaAs/GaAs distributed Bragg reflector for application to 1.3μm surface emitting laser diodes

A distributed Bragg reflector (DBR) utilizing the digital alloy Al_0.9Ga_0.1As was grown by using the molecular beam epitaxy (MBE) method for application in 1.3 μm optical communications and compared to the analog-alloy AlGaAs/GaAs DBR. The transmission electron microscopic (TEM) image showed a highly abrupt boundary of AlAs and GaAs, which supports the formation of a digital-alloy Al_0.9Ga_0.1As layer. The measurement showed that the digital-alloy AlGaAs/GaAs DBR had similar reflection spectra with enhanced uniform distribution over the whole substrate surface compared to the analog-alloy one. In the digital-alloy Al_0.9Ga_0.1As/GaAs DBR cavity, the reflection dip position was measured at around 1273 nm and the standard deviation of the distribution of the reflection dip was 1.31 nm in wavelength over 1/4 of a three-inch wafer.     

Reflective graphene oxide absorber for passively mode-locked laser operating at nearly 1μm

A low cost and simply fabricated reflective graphene oxide is successfully made. By using this absorber, as well as an end reflector, we obtain a passively mode-locked Yb:LuYSiO5 laser operating at nearly 1 μm. When the pump power is increased up to 5.73 W, stable mode locking is achieved. The central wavelength of the laser spectrum is 1043.2 nm with a pulse duration of 5.0 ps. When the pump power reaches 8.16 W, dual-wavelength mode locking laser pulses at 1036.3 nm and 1043.5 nm are simultaneously detected.     

Photoluminescence of Self－Assembled InAs／GaAs Quantum Dots Covered by InAlAs and InGaAs Combination Strain－Reducing Layer

Self-assembled lnAs/GaAs quantum dots covered by the 1-nm InxAI(1-x)As (x = 0.2, 0.3) and 3-nm In0.2Ga0.8As combination strain-reducing layer are fabricated, whose height can take up to 30-46 nm. The luminescence emission at a long-wavelength of 1.33μm and the energy separation between the ground and the first-excited state of 86meV are observed at room temperature. Furthermore, comparative study proves that the energy separation can increase to 91 meV by multiple stacking.     

Self-assembly of InAs quantum dots on GaAs(001)by molecular beam epitaxy

Currently, the nature of self-assembly of three-dimensional epitaxial islands or quantum dots (QDs) in a lattice-mismatched heteroepitaxial growth system, such as InAs/GaAs(001) and Ge/Si(001) as fabricated by molecular beam epitaxy (MBE), is still puzzling. The purpose of this article is to discuss how the self-assembly of InAs QDs in MBE InAs/GaAs(001) should be properly understood in atomic scale. First, the conventional kinetic theories that have traditionally been used to interpret QD self-assembly in heteroepitaxial growth with a significant lattice mismatch are reviewed briefly by examining the literature of the past two decades. Second, based on their own experimental data, the authors point out that InAs QD self-assembly can proceed in distinctly different kinetic ways depending on the growth conditions and so cannot be framed within a universal kinetic theory, and, furthermore, that the process may be transient, or the time required for a QD to grow to maturity may be significantly short, which is obviously inconsistent with conventional kinetic theories. Third, the authors point out that, in all of these conventional theories, two well-established experimental observations have been overlooked: i) A large number of “floating” indium atoms are present on the growing surface in MBE InAs/GaAs(001); ii) an elastically strained InAs film on the GaAs(001) substrate should be mechanically unstable. These two well-established experimental facts may be highly relevant and should be taken into account in interpreting InAs QD formation. Finally, the authors speculate that the formation of an InAs QD is more likely to be a collective event involving a large number of both indium and arsenic atoms simultaneously or, alternatively, a morphological/structural transformation in which a single atomic InAs sheet is transformed into a three-dimensional InAs island, accompanied by the rehybridization from the sp²-bonded to sp³- bonded atomic configuration of both indium and arsenic elements in the heteroepitaxial growth system.     

双层堆垛长波长InAs/GaAs量子点发光性质研究

研究了双层堆垛InAs/GaAs/InAs自组织量子点的生长和光致发光(PL)的物理性质。通过优化InAs淀积量、中间GaAs层厚度以及InAs量子点生长温度等生长条件,获得了室温光致发光1391～1438nm的高质量InAs量子点。研究发现对量子点GaAs间隔层实施原位退火、采用Sb辅助生长InGaAs盖层等方法可以增强高密度(2×1010 cm-2)InAs量子点的发光强度,减小光谱线宽,改善均匀性和红移发光波长。     

STEM-study of 1.3 μm InAs/InGaAs quantum dot structures

We investigated InAs-Dots-in-a-well structures emitting near 1.3 μm by bright field and Z-contrast mode in a scanning transmission electron microscope. The chemically sensitive Z-contrast mode is found to give direct information on the actual position of the InAs-Dots inside the embedding well, while the bright field mode monitors the strain fields. Comparing a series of structures, we found that the most symmetric design is realized by an nominally asymmetric growth. These symmetric structures exhibit the best performance with respect to photoluminescence spectra and laser threshold current density.     

GaSb/GaAs复合应力缓冲层上自组装InAs量子点的生长

研究了GaSb/GaAs复合应力缓冲层上自组装生长的InAs量子点.在2ML GaSb/1ML GaAs复合应力缓冲层上获得了高密度的、沿［100］方向择优分布量子点.随着复合应力缓冲层中GaAs层厚度的不同,量子点的密度可以在1.2×10¹⁰cm^-2和8×10¹⁰cm^-2进行调控.适当增加GaAs层的厚度至5ML,量子点的发光波长红移了约25nm,室温下PL光谱波长接近1300nm. 关键词： 自组装量子点 分子束外延 Ⅲ-Ⅴ族化合物半导体     

Single InAs/InP quantum dot spectroscopy in 1.3–1.55 μm telecommunication band

We present an optical spectroscopy and photon correlation measurement at telecommunication wavelengths performed on single InAs/InP quantum dots. Two main approaches brought high optical quality: an application of a ‘double-cap’ growth method to metalorganic chemical vapor deposition, and fabrication of a small mesa structure using low-damage wet chemical etching. Sharp and discrete exciton transition lines have been observed on the single quantum dots, which widely cover the spectral range of 1.3–1.55 μm. Using a pulsed excitation source and gated single-photon detection modules, we observed a photon antibunching behavior for an isolated exciton emission line, indicating nonclassical light emission near the wavelength of 1.3 μm.     

脉冲激光原位辐照对InAs/GaAs(001)量子点生长的影响

在InAs/GaAs(001)量子点生长过程中, 当InAs沉积量为0.9 ML时, 利用紫外纳秒脉冲激光辐照浸润层表面, 由于高温下In原子的不稳定性, 激光诱导的原子脱附效应被放大, 样品表面出现了原子层移除和纳米孔. 原子力显微镜测试表明纳米孔呈现以[110]方向为长轴(尺寸: 20-50 nm)、[110]方向为短轴(尺寸: 15-40 nm)的表面椭圆开口形状, 孔的深度为0.5-3 nm. 纳米孔的密度与脉冲激光的能量密度正相关. 脉冲激光的辐照对量子点生长产生了显著的影响: 一方面由于纳米孔的表面自由能低, 沉积的InAs优先迁移到孔内, 纳米孔成为量子点优先成核的位置; 另一方面, 孔外的区域因为In原子的脱附, 量子点的成核被抑制. 由于带有纳米孔的浸润层表面具有类似于传统微纳加工技术制备的图形衬底对量子点选择性生长的功能, 该研究为量子点的可控生长提供了一种新的思路.     

Photoluminescence and lasing properties of InAs/GaAs quantum dots grown by metal-organic chemical vapour deposition

Photoluminescence （PL） and lasing properties of InAs/GaAs quantum dots （QDs） with different growth procedures prepared by metalorganic chemical vapour deposition are studied. PL measurements show that the low growth rate QD sample has a larger PL intensity and a narrower PL line width than the high growth rate sample. During rapid thermal annealing, however, the low growth rate sample shows a greater blueshift of PL peak wavelength. This is caused by the larger InAs layer thickness which results from the larger 2-3 dimensional transition critical layer thickness for the QDs in the low-growth-rate sample. A growth technique including growth interruption and in-situ annealing, named indium flush method, is used during the growth of GaAs cap layer, which can flatten the GaAs surface effectively. Though the method results in a blueshift of PL peak wavelength and a broadening of PL line width, it is essential for the fabrication of room temperature working QD lasers.     

1.3μm GaInNAs量子阱RCE光探测器

采用配有dc-N plasma N源的分子束外延(MBE)技术在GaAs衬底上生长制作了工作波长为1,3μm的GaInNAs量子阱RCE探测器.采用传输矩阵法对器件结构进行优化.吸收区由三个GaInNAs量子阱构成,并用湿法刻蚀和聚酰亚胺对器件进行隔离.在零偏压下,器件最大的量子效率为12%,半峰值全宽(FWHM)为5.8nm,3dB带宽为30MHz,暗电流为2×10^-11A.通过对MBE生长条件和器件结构的优化,将进一步提高该器件的性能.     

High sensitivity Hall devices with AlSb/InAs quantum well structures

AlSb/InAs quantum well (QW) structures and InAs films on GaAs (001) substrates were grown by molecular beam epitaxy (MBE). We investigated the dependence of electron mobility and two-dimensional electron gas (2DEG) concentration on the thickness of an InAs channel. It is found that electron mobility as high as 19050 cm2·V-1·s-1 has been achieved for an InAs channel of 22.5 nm. The Hall devices with high sensitivity and good temperature stability were fabricated based on the AlSb/InAs QW structures. Their sensitivity is markedly superior to Hall devices of InAs films.