生长温度和结构参数对InGaAs／GaAs量子阱光学特性的影响

研究了不同生长温度下制备的In0.15Ga0.85As/GaAs应变量子阱的PL谱,结果表明,生长温度越高,In偏析和In-Ga互混越严重,同时,导致更多的In脱附,PL谱发光峰蓝移。对不同In含量的和不同InGaAs厚度的InGaAs/GaAs量子阱进行PL谱测试,分析表明In含量<0.2,生长温度低于560℃时,In含量和InGaAs层量子阱的厚度对In偏析、脱附和In-Ga互混基本没有影响。     

量子限制受主的光致发光研究

对一系列δ掺杂浅受主铍（Be）原子的GaAs/AlAs多量子阱和均匀掺杂Be受主的GaAs体材料中Be原子的能级间跃迁进行了光致发光（PL）研究.实验中所用的样品是通过分子束外延技术生长的均匀掺杂Be受主的GaAs外延单层样品和一系列GaAs/AlAs多量子阱样品,并在每量子阱中央进行了Be原子的δ掺杂,量子阱宽度为30 到200 ?.在4.2 K温度下测量了上述系列样品的光致发光谱,清楚地观察到了束缚激子的受主从基态1s_3/2（Γ₆）到第一激发态 关键词： 量子限制受主 光致发光 多量子阱 δ掺杂     

LP—MOCVD研制InGaAs/InP应变量子阱LD

本文指出在LP-MOCVD生长过程中,采用量子阱有源区和上限制层不同的生长温度以及生长非掺杂过渡层等技术能有效地控制InGaAs/InP量子阱激光器的p-n结结位,给出了采用DEZn和H₂S做掺杂源在InP材料中p型和n型杂质溶度和p-n结控制的条件,并研制出有源区阱层InGaAs与InP存在0.5%压缩应变量子阱激光器,这一结构LD实现室温脉冲激射,得到峰值功率为106mW以上,阈值电流密度为2.6kA/cm².     

InGaAs/GaAs应变量子阱的发光特性研究

利用低压金属有机化学气相沉积技术(LP-MOCVD)生长InGaAs/GaAs单量子阱(SQW),通过改变生长速率、优化生长温度和V/III比改善了量子阱样品的室温光致发光(PL)特性。测试结果表明,当生长温度为600℃、生长速率为1.15μm/h时,生长的量子阱PL谱较好,增加V/III比能够提高量子阱的发光强度。实验分析了在不同的In气相比条件下,生长速率对量子阱质量的影响,利用模型解释了高In气相比时,随着生长速率增加PL谱蓝移现象消失的原因。     

InGaAs/AlGaAs量子阱红外探测器中势垒生长温度的研究

InGaAs/AlGaAs量子阱是中波量子阱红外探测器件最常用的材料体系,本文以结构为2.4 nm In_(0.35)Ga_(0.65)As/40 nm Al_(0.34)Ga_(0.66)As的多量子阱材料为研究对象,利用分子束外延生长,固定InGaAs势阱的生长温度(465°C),然后依次升高分别选取465,500,545,580°C生长AlGaAs势垒层,从而获得四个不同的多量子阱样品.通过荧光光谱以及X射线衍射测试系统分析了势垒层生长温度对InGaAs量子阱发光和质量的影响,并较准确地给出了量子阱大致的温致弛豫轨迹:465—500°C,开始出现相分离,但缺陷水平较低,属弹性弛豫阶段;500—545°C,相分离加剧并伴随缺陷水平的上升,属弹性弛豫向塑性弛豫过渡阶段;545—580°C,相分离以及缺陷水平急剧上升,迅速进入塑性弛豫阶段,尤其是580°C时,量子阱的材料质量被严重破坏.     

具有InAlAs浸润层的InGaAs量子点的制备和特性研究

采用自组装方法生长了一种新型的InGaAs量子点/InAlAs浸润层结构.通过选取合适的In组分 ，使InAlAs浸润层的能级与GaAs势垒相当，从而使浸润层的量子阱特征消失.通过低温光致 发光（PL）谱的测试分析得到InGaAs量子点/InAlAs浸润层在样品中的确切位置.变温PL谱的 研究显示，具有这种结构的量子点发光峰的半高全宽随温度上升出现展宽，这明显区别于普 通InGaAs量子点半高全宽变窄的行为.这是因为采用了InAlAs浸润层后，不仅增强了对InGaA s量子点的限制作用，同时切断了载流子的 关键词： InGaAs量子点 InAlAs浸润层 PL谱     

高In组分InGaNAs/GaAs量子阱的生长及发光特性

采用分子束外延技术(MBE)在Ga As衬底上外延生长高In组分(40%)In Ga NAs/Ga As量子阱材料,工作波长覆盖1.3~1.55μm光纤通信波段。利用室温光致发光(PL)光谱研究了N原子并入的生长机制和In Ga NAs/Ga As量子阱的生长特性。结果表明:N组分增加会引入大量非辐射复合中心;随着生长温度从480℃升高到580℃,N摩尔分数从2%迅速下降到0.2%;N并入组分几乎不受In组分和As压的影响,黏附系数接近1;生长温度在410℃、Ⅴ/Ⅲ束流比在25左右时,In_(0.4)Ga_(0.6)N_(0.01)As_(0.99)/Ga As量子阱PL发光强度最大,缺陷和位错最少;高生长速率可以获得较短的表面迁移长度和较好的晶体质量。     

LP-MOCVD生长InGaAs/InP应变量子阱的研究

本文研究了LP-MOCVD对不同x值的In_1-xGa_xAs/InP生长条件,并且生长了压缩应变为0.5%三个不同阱宽的InGaAs/InP量子阱结构,利用77KPL光谱分析了能级同阱宽的关系,实现最窄阱宽为4.4nm,最小全半高峰宽为17.0mev.     

长波长大应变InGaAs/InGaAsP分布反馈激光器的材料生长与器件制备

采用低压金属有机化合物气相沉积法(LP-MOCVD)生长并制作了1.6—1.7μm大应变InGaAs/InGaAsP分布反馈激光器.采用应变缓冲层技术，得到质量良好的大应变InGaAs/InP体材料.器件采用了4个大应变的量子阱，加入了载流子阻挡层改善器件的温度特性.1.66μm和1.74μm未镀膜的3μm脊型波导器件阈值电流低(小于15mA)，输出功率高(100mA时大于14mW).从10—40℃，1.74μm激光器的特征温度T₀=57K，和1.55μm InGaAsP分布反馈激光器的特征温度相当. 关键词： MOCVD InGaAs/InGaAsP 应变量子阱 分布反馈激光器     

InGaAs/GaAsP应变补偿多量子阱MOCVD生长

利用金属有机化学气相沉积技术在GaAs衬底上开展了大失配InGaAs多量子阱的外延生长研究。针对InGaAs与GaAs之间较大晶格失配的问题,设计了GaAsP应变补偿层结构;通过理论模拟与实验相结合的方式,调控了GaAsP材料体系中的P组分,设计了P组分分别为0,0.128,0.184,0.257的三周期In_xGa_(1-x)As/GaAs_(1-y)P_y多量子阱结构;通过PL、XRD、AFM测试对比发现,高势垒GaAsP材料的张应变补偿可以改善晶体质量。综合比较,在P组分为0.184时,PL波长1 043.6 nm,半峰宽29.9 nm, XRD有多级卫星峰且半峰宽较小,AFM粗糙度为0.130 nm,表面形貌显示为台阶流生长模式。     

Influence of semiconductor cap layer on the impurity-free vacancy disordering of the In<Subscript>0.2</Subscript>Ga<Subscript>0.8</Subscript>As/GaAs multiquantum-well structure by dielectric capping layers

The feasibility of normal GaAs, low-temperature-grown GaAs (LT-GaAs) and low-temperature-grown InGaAs (LT-InGaAs) as the capping layers for impurity-free vacancy disordering (IFVD) of the In_0.2Ga_0.8As/GaAs multiquantum-well (MQW) structure has been studied. The normal GaAs, LT-GaAs and LT-InGaAs layers were tested as the outermost capping layer and the intermediate cap layer underneath the SiO₂ or Si₃N₄ capping layer. The degree of quantum-well intermixing (QWI) induced by rapid thermal annealing was estimated by the shift of the photoluminescence (PL) peak energy. It was found that the IFVD of the In_0.2Ga_0.8As/GaAs MQW structure using LT-GaAs (LT-InGaAs) as the outermost capping layer was much smaller (larger) than that using a SiO₂ (Si₃N₄) capping layer. It was also observed that the insertion of the normal GaAs, LT-GaAs and LT-InGaAs cap layers below the SiO₂ or Si₃N₄ capping layer reduces the degree of QWI and the PL intensity after the QWI. A plausible explanation for the influence of normal GaAs, LT-GaAs and LT-InGaAs cap layers for the QWI of the InGaAs/GaAs structure is also discussed. PACS 68.55.Ln; 73.20.Dx; 78.55.-m     

Structural and optical properties of In0.5Ga0.5As/GaAs quantum dots in an In0.1Ga0.9As well using repeated depositions of InAs/GaAs short-period superlattices for the application of optical communication

We report structural and optical properties of In_0.5Ga_0.5As/GaAs quantum dots (QDs) in a 100 Å-thick In_0.1Ga_0.9As well grown by repeated depositions of InAs/GaAs short-period superlattices with atomic force microscope, transmission electron microscope (TEM) and photoluminescence (PL) measurement. The QDs in an InGaAs well grown at 510 °C were studied as a function of n repeated deposition of 1 monolayer thick InAs and 1 monolayer thick GaAs for n=5–10. The heights, widths and densities of dots are in the range of 6–22.0 nm, 40–85 nm, and 1.6–1.1×10¹⁰/cm², respectively, as n changes from 5 to 10 with strong alignment along [1 −1 0] direction. Flat and pan-cake-like shape of the QDs in a well is found in TEM images. The bottoms of the QDs are located lower than the center of the InGaAs well. This reveals that there was intermixing—interdiffusion—of group III materials between the InGaAs QD and the InGaAs well during growth. All reported dots show strong 300 K-PL spectrum, and 1.276 μm (FWHM: 32.3 meV) of 300 K-PL peak was obtained in case of 7 periods of the QDs in a well, which is useful for the application to optical communications.     

Improvement of the optical property and uniformity of self-assembled InAs/InGaAs quantum dots by layer-by-layer temperature and substrate rotation

The influence of layer-by-layer temperature and substrate rotation on the optical property and uniformity of self-assembled InAs/In_0.2Ga_0.8As/GaAs quantum dots (QDs) gown with an As₂ source was investigated. An improvement in the optical property of QDs was obtained by the precise control and optimization of growth temperature utilized for each layer, i.e., InAs QDs, InGaAs quantum wells, GaAs barriers and AlGaAs layers, respectively. By using a substrate rotation, the QD density increased from ∼1.4×10¹⁰ to ∼3.2×10¹⁰ cm⁻² and its size also slightly increased, indicating a good quality of QDs. It is found that the use of an appropriate substrate rotation during growth improves the room-temperature (RT) optical property and uniformity of QDs across the wafer. For the QD sample with a substrate rotation of 6 rpm, the RT photoluminescence (PL) intensity is much higher and the standard deviation of RT-PL full-width at half-maximum is decreased by 35% compared to that grown without substrate rotation.     

Quantum point contacts on InGaAs/InP heterostructures

For the first time we have observed quantized conductance in a split gate quantum point contact prepared in a strained In_0.77Ga_0.23As/InP two-dimensional electron gas (2DEG). Although quantization effects in gated two-dimensional semiconductor structures are theoretically well known and proven in various experiments on AlGaAs/GaAs and also on In_0.04Ga_0.96As/GaAs, no quantum point contact has been presented in the InGaAs/InP material with an indium fraction as high as 77% so far. The major problem is the comparatively low Schottky barrier of the InGaAs (φ_B≈ 0.2 eV) making leakage-free gate structures difficult to obtain. Nevertheless this heterostructure—especially with the highest possible indium content—has remarkable properties concerning quantum interference devices and semiconductor/superconductor hybrid devices because of its large phase coherence length and the small depletion zone, respectively. In order to produce leakage-free split gate point contacts the samples were covered with an insulating SiO₂layer prior to metal deposition. The gate geometry was defined by electron-beam lithography. In this paper we present first measurements of a point contact on an In_0.77Ga_0.23As/InP 2DEG clearly showing quantized conductance.     

InAs/AlAs quantum dots with InGaAs insertion layer: dependence of the indium composition and the thickness

We have systematically studied the effect of an In_xGa_1−xAs insertion layer (IL) on the optical and structural properties of InAs quantum dot (QD) structures. A high density of 9.6×10¹⁰ cm⁻² of InAs QDs with an In_0.3Ga_0.7As IL has been achieved on a GaAs (1 0 0) substrate by metal organic chemical vapor deposition. A photoluminescence line width of 25 meV from these QDs has been obtained. We attribute the high density and high uniformity of these QDs to the use of the IL. Our results show that the InGaAs IL is useful for obtaining high-quality InAs QD structures for devices with a 1.3 μm operation.     

Electro-absorption modulator using a type-II quantum well in the InxGa1 − xAs/InAlAs/InP system

In this paper photoluminescence measurements at low temperature under different excitation powers were carried out on an InGaAs tensile strained (x =  0.3) quantum well with InGaAs barriers lattice matched (LM) to InP. Evidence of a type-II recombination was found between carriers confined in the tensile layer and in the LM layer. This study allows us to deduce an accurate determination of the conduction band offset in the In_0.3Ga_0.7As/In_0.53Ga_0.47As/InP system. Moreover, we include the previous type-II structure between InAlAs barriers in order to confine both electrons and holes. This structure has potential applications in electro-optical modulators. We simulate its optical modulation by solving the Schrödinger equation using the envelope function approximation and calculating the absorption spectrum taking into account excitonic effects.     

Efficient photoluminescence from triangular quantum wells at the interface of an InP/In0.53Ga0.47As heterostructure

Efficient photoluminescence (PL) with quantum yield close to 1 from InP/In_0.53Ga_0.47As heterostructures (HSs) at temperatures 77–300 K and low excitation levels is observed and investigated. The PL is due to a quasi-triangular quantum well (TQW) located at the HS interface and consists of two spectrally similar lines: InGaAs interband emission and emission from the bottom level of the TQW. It is found that as the temperature increases, the intersubband emission rises, while the TQW radiation is quenched. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 10, 783–787 (25 May 1998)     

Optical and transport properties of δ-doped pseudomorphic AlGaAs/InGaAs/GaAs structures

We investigate the effects of spacer layer thickness on the optical and transport properties of the n-type-doped pseudomorphic Al_0.30Ga_0.70As/In_0.15Ga_0.85As / GaAs structures. A-doped AlGaAs/InGaAs/GaAs structure with a 6nm spacer layer yields a sheet carrier concentration of 1.5×10¹² cm^–2 at 77K with electron mobility of 6.4×10³ cm²/Vs, 3.11×10⁴ cm²/Vs, and 3.45×10⁴ cm²/Vs at room temperature, 77 and 20K, respectively. The effects of the different scattering mechanisms on luminescence linewidth and electron mobility have also been discussed.     

Spontaneous one-dimensional lateral alignment of multistacked InGaAs quantum dots on GaAs (n 1 1)B substrates

In_0.45Ga_0.55As/GaAs multistacking quantum dot (QD) structures were fabricated on a GaAs (n 1 1)B (n=2–4) substrate by metalorganic vapor-phase epitaxy. QDs spontaneously aligned in the [0 1 1] direction were observed on stacked QDs, whereas QDs were randomly distributed in the initial In_0.45Ga_0.55As layer growth. The formation mechanism of this self-alignment was studied by changing the number of In_0.45Ga_0.55As/GaAs multilayers and crystallographic arrangement. Photoluminescence spectra showing clear polarization dependence indicate carrier coupling in the QD arrays. This growth technique results in spontaneously aligned InGaAs QDs without any preprocessing technique prior to growth.     

High-k Al2O3 MOS structures with Si interface control layer formed on air-exposed GaAs and InGaAs wafers

This paper attempts to realize unpinned high-k insulator-semiconductor interfaces on air-exposed GaAs and In_0.53Ga_0.47As by using the Si interface control layer (Si ICL). Al₂O₃ was deposited by ex situ atomic layer deposition (ALD) as the high-k insulator. By applying an optimal chemical treatment using HF acid combined with subsequent thermal cleaning below 500 °C in UHV, interface bonding configurations similar to those by in situ UHV process were achieved both for GaAs and InGaAs after MBE growth of the Si ICL with no trace of residual native oxide components. As compared with the MIS structures without Si ICL, insertion of Si ICL improved the electrical interface quality, a great deal both for GaAs and InGaAs, reducing frequency dispersion of capacitance, hysteresis effects and interface state density (D_it). A minimum value of D_it of 2 × 10¹¹ eV⁻¹ cm⁻² was achieved both for GaAs and InGaAs. However, the range of bias-induced surface potential excursion within the band gap was different, making formation of electron layer by surface inversion possible in InGaAs, but not possible in GaAs. The difference was explained by the disorder induced gap state (DIGS) model.