玻璃中半导体CdSSe量子点的界面态发光

研究了玻璃中半导体Cd SSe量子点的界面态发光.在10 K温度下,通过PL 和吸收光谱实验,研究了半导体Cd SSe量子点,并进行了变温测量.分析了半导体量子点的量子尺寸效应、温度对PL 和吸收光谱的影响.实验发现PL 谱中在1.84e V和1.91e V有两个尖锐的发光峰,且峰位不随量子点尺寸大小变化而漂移,这是来源于与量子点尺寸无关的界面态的发光;同时,界面态的发光强度应与量子点半径成反比,实验结果与之相符.     

玻璃中半导体CdSSe量子点的界面态发光

研究了玻璃中半导体CdSSe量子点的界面态发光.在10K温度下,通过PL和吸收光谱实验,研究了半导体CdSSe量子点,并进行了变温测量.分析了半导体量子点的量子尺寸效应、温度对PL和吸收光谱的影响.实验发现PL谱中在1.84eV和1.91eV有两个尖锐的发光峰,且峰位不随量子点尺寸大小变化而漂移,这是来源于与量子点尺寸无关的界面态的发光;同时,界面态的发光强度应与量子点半径成反比,实验结果与之相符.     

多孔硅上生长Ge量子点的光学特性

采用量子尺寸的多孔硅作为衬底 ,利用区域优先成核在多孔硅表面上成功地生长了 Ge量子点 .由于量子限制效应锗的 PL 谱发生了明显的蓝移 ,计算表明在傅里叶红外光谱中观察到的中红外 (5— 6 μm)吸收峰是源于量子点中的亚能带跃迁 (两个重空穴能级之间的跃迁 ) ,这为 Ge量子点红外光探测器的应用提供了理论基础     

锗硅双层量子点的光电流特性

在分子束外延 (MBE)系统上用自组织方式生长了硅基双层锗量子点结构 ,并对样品进行光电流谱的测试。通过调节不同外加偏压来改变量子点中的费米能级位置 ,量子点中载流子所处束缚能级将随之发生变化 ,所得到的光电流谱的峰位也将因此而改变。由光电流谱得到的实验结果与常规的光致发光谱的结果相吻合。与单层锗量子点结构相比 ,双层结构的样品在光电特性上有着明显不同 :光电流谱中 ,在 0 .767e V及 0 .869e V处出现了两个峰 ,分别对应于载流子在不同的量子点层中的吸收。用这种结构的样品制成的红外光探测器能够同时对两种不同波长的光进行探测响应     

多孔硅上生长Ge量子点的光学特性

采用量子尺寸的多孔硅作为衬底,利用区域优先成核在多孔硅表面上成功地生长了Ge量子点.由于量子限制效应锗的PL谱发生了明显的蓝移,计算表明在傅里叶红外光谱中观察到的中红外(5-6μm)吸收峰是源于量子点中的亚能带跃迁(两个重空穴能级之间的跃迁),这为Ge量子点红外光探测器的应用提供了理论基础.     

自组织InAs/GaAs量子点的表面氮化研究

用低温光荧光(PL)和透射电子显微镜(TEM)研究了表面氮化自组织InAs/GaAs量子点的光学性能和微观结构。结果表明氮化后形成薄层的InAsN薄膜作为应变缓和层覆盖在量子点的表面,使得随着氮化时间的增加,InAs量子点的位错密度提高、尺寸变大、纵横比提高、发光波长变长、强度变低。     

多层Ge量子点的生长及其光学特性

用超高真空化学气相淀积系统在Si(1 0 0 )衬底上生长了多层Ge量子点.分别用TEM和AFM分析了埋层和最上层量子点的形貌和尺寸,研究了量子点层数和Si隔离层厚度对上层Ge量子点的形状和尺寸分布的影响.观察到样品的低温PL谱线有明显蓝移(87meV) ,Ge量子点的PL谱线的半高宽度(FWHM )为46meV ,说明采用UHV/CVD生长的多层量子点适合量子光电器件的应用     

多层Ge量子点的生长及其光学特性

用超高真空化学气相淀积系统在Si(100)衬底上生长了多层Ge量子点.分别用TEM和AFM分析了埋层和最上层量子点的形貌和尺寸,研究了量子点层数和Si隔离层厚度对上层Ge量子点的形状和尺寸分布的影响.观察到样品的低温PL谱线有明显蓝移(87meV),Ge量子点的PL谱线的半高宽度(FWHM)为46meV,说明采用UHV/CVD生长的多层量子点适合量子光电器件的应用.     

InGaAs／GaAs自组织量子点光致发光特性研究

用PL谱测试研究了GaAs和不同In组份InxGa1-xAs(x=0.1,0.2,0.3)覆盖层对分子外延生长的InAs/GaAs自组织量子点发光特性的影响,用InxGa1-xAs外延层覆盖InAs/GaAs量子点,比用GaAs做 其发光峰能量向低有端移动,发光峰半高度变窄,量子点发光峰能量随温度的红移幅度较小,理论计算证实这是由于覆盖层InxGa1-xAs减小了InAs表面应力导致发光峰红移,而In元素有效抑制了InAs/GaAs界面组份的混杂,量子点的均匀性得到改善,PL谱半高宽变窄,用InGaAs覆盖的In0.5Ga0.5As/GaAs自组织量子点实现了1．3μm发光,室温下PL谱半高宽为19．2meV,是目前最好的实验结果。     

表面应力诱导InGaN量子点的生长及其性质

为了得到高性能的GaN基发光器件,有源层采用MOCVD技术和表面应力的不均匀性诱导方法生长了InGaN量子点,并通过原子力显微镜(AFM)、透射电子显微镜(TEM)和光致发光(PL)谱对其微观形貌和光学性质进行了观察和研究.AFM和TEM观察结果表明:InGaN/GaN为平均直径约30nm,高度约25nm的圆锥;InGaN量子点主要集中在圆锥形的顶部,其密度达到5.6×1010cm-2.室温下,InGaN量子点材料PL谱强度大大超出相同生长时间的InGaN薄膜材料,这说明InGaN量子点有望作为高性能有源层材料应用于GaN基发光器件.     

基于微纳结构的硅基高速探测器研究进展

传统平面入射型硅基探测器由于近红外吸收系数低,存在响应速度和探测效率的冲突,被认为不适用于短距离光纤通信领域。微纳结构可有效提高等效光程,使入射光被吸收层充分吸收,提高光电器件的量子效率,广泛应用于太阳电池、近红外增强探测器等领域。近期,研究者基于陷光微结构,实现了数据传输速率达20Gb/s以上、与CMOS工艺兼容的硅基高速探测器,展现出了广阔的发展前景。文章对微纳结构的优化设计、制备方法、基于微纳结构的硅基高速探测器的研究进展进行了综述和分析。     

Specific features of photoelectric and optical properties of amorphous hydrogenated silicon films produced by plasmochemical deposition from monosilane–hydrogen mixture

Photoelectric and optical properties of amorphous hydrogenated silicon films produced by plasmochemical deposition from a monosilane-hydrogen mixture have been studied at a fraction of hydrogen in the mixture that corresponds to the onset of formation of a nanocrystalline phase in the structure of the films obtained. A behavior untypical of amorphous hydrogenated silicon films is observed for the photoconductivity and the spectral dependence of the absorption coefficient. The temperature dependences of the photoconductivity in the films under study are found to vary with the energy of incident photons. At a photon energy of 1.3 eV, temperature quenching of photoconductivity is observed. Prolonged illumination of the films led to a certain decrease in the absorption coefficient at photon energies in the range 1.2–1.5 eV. The results obtained are attributed to the possible presence of silicon nanocrystals in the structure of the films and to the influence of these nanocrystals on their photoelectric and optical properties.     

A nanostructured copper telluride thin film grown at room temperature by an electrodeposition method

Copper telluride onion flower like microstructures,constructed by quantum dots with various diameters,were obtained by a potentiostatic electrodeposition method at room temperature.The structural,optic...     

Two-Photon Photovoltaic Effect in Silicon

Optical amplification, wavelength conversion, and a myriad of other functions that were once considered to be beyond silicon's reach have been made possible by the material's nonlinear optical properties. The common feature of such devices is the high optical intensity that is required to induce the nonlinear optical interactions. Concurrent with the useful nonlinearities (Raman and Kerr) are two-photon absorption and free carrier scattering, which are two related and harmful phenomena that render silicon lossy at high intensities. This paper explores the use of the two-photon photovoltaic effect as a means to counter these phenomena in an energy-efficient manner. The effect reduces losses due to free carrier scattering and serendipitously scavenges the optical energy lost to two-photon absorption. Analytical and numerical modeling of the two-photon photovoltaic effect in silicon devices is presented. The model is validated through comparison with experimental results and is used to establish the limits of this approach for creating energy-efficient silicon photonic devices.     

Theoretical studies of optical modulation in lattice matched and strained quantum wells due to transverse electric fields

Electrooptical modulators based on quantum well structures have become an important area of research due to potential applications in high-speed optical modulation and image processing. In this paper, we examine the physics of a quantum well modulator within the generalized Kohn-Luttinger Hamiltonian. Issues of importance for the modulator structure are the excitonic absorption shift, exciton binding energy, line broadening, tunneling rates for electrons and holes in the presence of a transverse electric field, and changes in optical absorption coefficients as a function of electric field. A formalism to study these effects for both lattice matched and nonlattice matched quantum well structures is provided and the potential of material tailoring for specific optical response is discussed. It is shown that the reliability of this technology is critically related to the fabrication of high-quality interfaces and alloys since even a one-monolayer variation in quantum well size can have a substantial effect on the modulation properties.     

Design and performance of an erbium-doped silicon waveguide detector operating at 1.5 /spl mu/m

A new concept for an infrared waveguide detector based on silicon is introduced. It is fabricated using silicon-on-insulator material, and consists of an erbium-doped p-n junction located in the core of a silicon ridge waveguide. The detection scheme relies on the optical absorption of 1.5-/spl mu/m light by Er/sup 3+/ ions in the waveguide core, followed by electron-hole pair generation by the excited Er and subsequent carrier separation by the electric field of the p-n junction. By performing optical mode calculations and including realistic doping profiles, we show that an external quantum efficiency of 10/sup -3/ can be achieved in a 4-cm-long waveguide detector fabricated using standard silicon processing. It is found that the quantum efficiency of the detector is mainly limited by free carrier absorption in the waveguide core, and may be further enhanced by optimizing the electrical doping profiles. Preliminary photocurrent measurements on an erbium-doped Si waveguide detector at room temperature show a clear erbium related photocurrent at 1.5 /spl mu/m.     

Tb3+-Yb3+离子对的近红外量子剪裁进展研究

近红外量子剪裁能够有效地提高硅太阳能电池的效率。稀土元素种类繁多,能级丰富,常被用于制作近红外量子剪裁发光材料。研究者们用适当的方法制成发光材料之后,测量材料的吸收光谱,激发光谱和发射光谱。根据这些数据计算得到材料的量子效率。其中Tb3+-Yb3+离子对备受关注。Tb3+吸收紫外-可见光,通过协同能量传递把能量传递给Yb3+离子。Yb3+离子跃迁辐射出1000nm左右的近红外光。该波段的光子能够被硅太阳能电池吸收利用。Tb3+-Yb3+离子对在不同掺杂浓度,不同基质中得到的量子效率不同。     

Calculation of linear and nonlinear intersubband optical absorptions in a quantum well model with an applied electric field

Analytic forms of the linear and the third-order nonlinear optical intersubband absorption coefficients are obtained for general asymmetric quantum well systems using the density matrix formalism, taking into account the intrasubband relaxation. Based on this model, we calculate the electric field dependence of the linear and the third-order nonlinear intersubband optical absorption coefficients of a semiconductor quantum well. The energy of the peak optical intersubband absorption is around 100 meV (wavelength is 12.4 μm). Thus, electrooptical modulators and photodetectors in the infrared regime can be built based on the physical mechanisms discussed here. The contributors to the nonlinear absorption coefficient due to the electric field include 1) the matrix element variation and 2) the energy shifts. Numerical results are illustrated.     

Switch energy requirements for first- and second-orderperturbations in asymmetric quantum box optical switches

We have studied the limits to the switching energy of electrically controlled optical absorption switches. Investigating a case with intraband transitions in asymmetric quantum boxes, it is shown that linear Stark shift allows switch energies of the optical switches that are comparable to the thermal noise limit at 300 K at least up to 30 GHz, provided boxes with very narrow absorption linewidth can be fabricated. This is several orders of magnitude lower energy than required by quadratic Stark shift in a similar, symmetric structure     

正切平方势阱中线性和三阶非线性光学吸收系数的计算

研究了正切平方势阱中的子带光吸收,用量子力学中的密度矩阵算符理论和迭代法推导出了正切平方势阱中线性和三阶非线性光学吸收系数的解析表达式,并以典型的GaAs/AlGaAs正切平方量子阱为例进行数值计算。计算结果表明,该势阱中的势阱宽度b、势阱深度V₀和入射光强I对吸收系数有很大影响。随着势阱宽度b的增加和势阱深度V₀的减小,总吸收系数的峰值减小并且向低能方向移动。随着入射光强I的增加,总吸收系数会减小,出现了光饱和吸收现象,同时吸收谱线的线宽随着入射光强的增大而增大。