InGaAsSb多量子阱材料的光致发光特性研究

研究了InGaAsSb多量子阱材料光致发光特性。通过实验数据分析和理论计算,发现对于分子束外延(MBE)法生长的InGaAsSb多量子阱材料,生长时的衬底温度决定着材料的质量,合适的衬底温度可以明显的增加其发射的光致发光强度;组分相同时,在一定范围内,随着阱厚的增加,其发射的光致发光波长也随着增加,但是随着阱厚增大,波长增加趋于平缓。     

调制掺杂Al0.27Ga0.73As/GaAs多量子阱结构的光致发光

在调制掺杂（Si）Al0.27Ga0.73As／GaAs多量子阱结构的光致发光谱中，观测到一个强发光峰及多个低能弱发光峰．强发光峰是量子阱中基态电子与重空穴复合，即激子复合形成的，其低温发光线形可用Voigt函数拟合.低能弱峰是势垒层Al0.27Ga0.73As中DX中心能级上的电子跃迁到SiAs原子而引起，由此确定DX中心有四个能级，其激活能分别为0．35、037、0．39、0．41eV     

GaSb/InGaAsSb量子阱的带间跃迁设计

采用一维方势阱模型对Gash/InxGa1-xAs0.02Sb0.98m量子阱激光器结构的子带跃迁波长与阱宽间的关系进行了计算,并采用能量平衡模型计算了此应变材料体系在生长时的临界厚度.结果表明GaSb/InGaAsSb是制作2～3μm中红外波段量子阱激光器的良好材料体系.在结构设计和材料生长中采用合适的材料组分及阱宽并对应变总量进行控制是十分重要的.     

GaAs多量子阱的光电流谱

在Ｔ＝７７Ｋ，测量了ＧａＡｓ多量子阱的光电流，发现在ｖ＝１３１２ｃｍ＾－１附近存在一个强电流峰，并且在这强电流峰附近的高波数区还有几个弱峰，强电流峰是量子阱中基态电子向第一激发态跃迁形成的，而弱峰与最子阱势垒以上的电子干涉有关。     

GaxIn1-xAs/GaInAsP应变量子阱结构能带的计算

对含有Luttinger-Kohn哈密顿量的有效质量方程，利用S.L.Chuang提出的传递矩阵法，计算了量子阱中不同Ga组分的GaxIn1-xAs/GaInAsP应变量子阱结构的能带，该结构可被选作980nm光通信泵浦激光器的有源层，研究还得到了GaxIn1-xAs/GaInAsP双应变量子阱结构中电子和空穴的能级以及能级的色散关系。     

LP-MOCVD生长大功率InGaAsP/GaAs量子阱激光器

设计并利用LP－MOCVD生长了InGaAsP/GaAs分别限制单量子阱结构,采用无铝的InGaP做光学包层。腔面未镀膜情况下,测试10支条宽100μm,腔长1mm的激光器样品,连续输出功率超过1W,阈值电流密度为330～490A/cm2,外微分量子效率为55％～78％,中心发射波长为(808±3)nm。     

高功率GaAs/GaAlAs单量子阱远结激光器

通过对５０余只８０８ｎｍ的ＧａＡｓ／ＧａＡｌＡｓ高功率单量子阱远结半导体激光器的老化实验观测,在老化初期（前５２０ｈ）,阈值电流随老化时间的延长而下降,下降幅度高达５７ｍＡ,从１０００ｈ多的恒流电老化结果可以看出,器件的输出光功率在老化初期有所上升,随后,表现出按指数规律缓慢下降的行为。初步实验结果表明器件具有长寿命的潜力。     

1.3μmInAsP/InGaAsP应变补偿量子阱激光器

采用气态源分隔束外延方法及应变补偿生长工艺生长了ＩｎＡｓＰ／ＩｎＧａＡｓＰ应变补偿多量子阱激光器材料,采用选择刻蚀和聚酰亚胺隔离工艺制成了脊波导型１．３μｍ激光器芯片并对芯片性能进行了统计测量,测量结果表明此种激光器芯片在室温下的阈值电流可小于１０ｍＡ,在２５℃至９０℃温度范围内特征温度大于９０Ｋ,并表现出较好的单纵模特性。     

用离子注入的方法实现InGaAs/InGaAsP激光器材料的量子阱混合

为了在光开关器件的局部区域实现量子阱混合,选用1～2MeV、1×1013～5×1013cm－2的P＋离子注入到InGaAs/InGaAsP分别限制多量子阱（SCH－MQW）激光器结构,在700oC下快速热退火90s。发现光致发光谱的峰值位置发生蓝移9～89nm。蓝移的大小随着注入能量和剂量的增大而增大,并且能量比剂量对蓝移的影响更大。     

InGaAs／InAlAs多量子阱电吸收光调制器

在国内首次设计并制作了脊波导结构的Ｉｎ０．５３Ｇａ０．４７Ａｓ／Ｉｎ０．５２Ａｌ０．４８Ａｓ多量子阱电吸收型光调制器，并对它的工作特性进行了测试。在３．０Ｖ的驱动电压下实现了２０ｄＢ以上的消光比，光３ｄＢ带宽达到了３ＧＨｚ，对限制光调制器带宽的主要原因进行了分析，结果表明器件电容限制了带宽的提高，这主要是由于ＳｉＯ２刻蚀液的钻蚀导致ＳｉＯ２绝缘层厚度减小造成的。改进制作工艺可望大大改善调制器的工作     

InGaAsP/InP long wavelength quantum well infrared photodetectors

High quality InGaAsP/InP MQWs structures, grown by solid source molecular beam epitaxy, with different doping concentrations in the wells were investigated. High doping concentrations benefits absorption but is not good for dark current. The photocurrent spectra and peak values are sensitive to applied voltage. The total photocurrent comes from the electrons excited to two excited states. The decrease of the photocurrent peak value at high voltage can be explained by the reduction of photogenerated electrons. The detectivity of the InGaAsP/InP QWIP measured at a bias of − 2.5 V at 20 K is greater than , which is comparable to the GaAs/AlGaAs QWIPs.     

Investigation of V-defects formation in InGaN/GaN multiple quantum well grown on sapphire

In the growth of InGaN multiple quantum well structure, V-pits has been observed to be initiated at the threading dislocations which propagate to the quantum well layers with high indium composition and substantially thick InGaN well. A set of samples with varying indium well thickness (3-7.6 nm) and composition (10-30%) are grown and characterized by photoluminescence (PL), X-ray diffraction, transmission electron microscopy and atomic force microscopy. The indium content and the layer thicknesses in InGaN/GaN quantum well are determined by high-resolution X-ray diffraction (XRD) and TEM imaging. With indium composition exceeding 10%, strain at the InGaN/GaN interface leads to the generation of V-pits at the interlayers of the MQW. Higher indium composition and increase in thickness of a period (InGaN well plus the GaN barrier) appear to enhance pits generation. With thicker InGaN well and reduction in thickness of GaN to InGaN (or the R ratio), pit density is substantially reduced, but it results in greater inhomogeneity in the distribution of indium in the InGaN well. This leads to a broadened PL emission and affect the PL emission intensity.     

InAs/GaAs multiple quantum dot structures grown by LP-MOVPE

Structures with self-organised InAs quantum dots in a GaAs matrix were grown by the low pressure metal–organic vapour phase epitaxy (LP-MOVPE) technique. Photoluminescence and atomic force microscopy were used as the main characterisation methods for the growth optimisation. The properties of multiple-stacked quantum dot structures are influenced by the thickness of the GaAs separation layers (spacers) between quantum dot-containing InAs layers, by the InAs layer thickness, by arsine partial pressure during growth, and by group III precursor flow interruption time.     

Electrooptical properties of GaNAs/GaAs multiple quantum well structures

The electrooptical properties of the GaNAs/GaAs multiple quantum well structures have been studied using the photoreflectance spectroscopy from 20 K to room temperature. Above the band gap energy of GaAs, Franz–Keldysh oscillations were observed. The period of the Franz–Keldysh oscillations decreased slightly with decreasing temperature, and indicated that the corresponding space charge distribution varied slowly with temperature. The modulated quantum well transition features were observed below the band gap energy of GaAs. A matrix transfer algorithm was used to calculate the quantum well subband energies numerically. The band gap energy and the electron effective mass of the GaNAs/GaAs system were adjusted to obtain the subband energies to best fit the observed quantum well transition energies.     

Band offsets of InXGa1−XN/GaN quantum wells reestimated

Recently In_XGa_1−XN/GaN heterostructures and quantum wells (QWs) have gained immense importance in the application of III-V nitride materials. Reported values of the ratios of conduction band offset to valence band offset for In_XGa_1−XN/GaN QW structures, ΔE_c:ΔE_v, vary widely from 38:62 to 83:17. While trying to explain the unusual shifts in the photoluminescence (PL) spectra, obtained from In_XGa_1−XN/GaN QW structures, it has been found that a band offset ratio, ΔE_c:ΔE_v = 55:45, explains all the experimental data precisely. In this paper detailed theories, procedures, results and discussions to establish the newly estimated band offsets will be presented.     

Photoluminescence characterization of InGaP/GaAs/InGaP quantum wires

We investigated the photoluminescence of InGaP/GaAs/InGaP heterostructures with the aim to prepare quantum wires by the epitaxial overgrowth of V-groove patterned substrates. Planar and V-groove patterned GaAs semiinsulating substrates were used for epitaxial growth in a low-pressure MOVPE equipment with a horizontal reactor. Low temperature photoluminescence measurements show that the composition of the InGaP ternary compound prepared on the patterned substrates is shifted to a higher InP mole fraction compared with the planar ones. On the other hand, the measurement on the V-grooved samples showed that the PL peak is shifted to higher energies (i.e. to the higher amount of Ga), which indicates a change in the ternary composition of about 5%. Crystalline quality of the overgrown structures was studied by transmission electron microscopy. Both, photoluminescence and photoluminescence polarization measurement show that quantum wires can be successfully prepared in the InGaP/GaAs/InGaP system.     

Photoluminescence studies of CdTe films and junctions

Device quality CdTe films and junctions have been studied using low-temperature photoluminescence (PL) measurements. The behavior of the PL was studied as a function of the measurement temperature and excitation intensity. The CdTe films and junctions were prepared under various deposition conditions to determine the effect of film deposition and solar cell fabrication parameters, such as the effect of oxygen, and chloride treatment. A PL band located at 1.232 eV has been attributed to the presence of oxygen. This band is present only in as-deposited samples excited at the CdTe surface. Samples annealed in the presence of CdCl₂ exhibit a single PL band located at 1.42 eV. A model explaining the behavior of these bands is presented.     

Explanation of Unusual Photoluminescence Behavior from InAs Quantum Dots with InAlAs Capping

The effect of different kinds of cap layers on optical property of InAs quantum dots (QDs) on GaAs (100) substrate was studied. Temperature dependent photoluminescence (PL) indicates that the PL integrated intensity from the ground state of InAs QDs capped with an intermediate InAIAs layer drops very little as compared to QDs capped with a thin InGaAs or GaAs cap layer from 15 K up to room temperature. PL integrated intensity ratio of the first excited to ground states for InAs QDs capped with an intermediate InAIAs layer is unexpectedly decreased with increasing temperature, which are attributed to phonon bottleneck effect. A virtual barrier is proposed to describe this physics process and shows good agreement with experimental results when fitting the curve with the value of the virtual barrier 30 meV.     

Magnetic-field tuning of the alloy-induced disorder in quaternary semimagnetic (Zn, Cd, Mn)Se quantum well structures

The influence of magnetic-field-induced tuning of the disorder on the line width of the lowest excitonic transition in diluted magnetic semiconductor (Zn, Cd, Mn)Se/ZnSe quantum well samples is studied by photoluminescence at 2 K and in magnetic fields up to 7.5 T. It is shown that the dependence of the photoluminescence line width on quantum well thickness can be explained as a sum of contributions of ZnSe barrier, (Zn, Cd, Mn)Se well and the interfaces.