A 1280 × 1024 CMOS visible-range photodetector chip with a pixel size of 13 × 13 μm

A photodetector array chip for detection of the optical signal in a wave range of 0.4–1.0 μm; conversion of the optical signal into the electric signal; and its extraction in the analog form to 1, 2, 4, 8, or 16 outputs has been designed, fabricated, and studied. The main parameters of this chip are the following: the charge capacity is up to 200000 electrons, the frame rate is higher than 600 Hz at the maximum resolution, and the integrated sensitivity is up to 1000 V/(lx s).     

Electron mobility and effective mass in composite InGaAs quantum wells with InAs and GaAs nanoinserts

The paper is concerned with the theoretical and experimental studies of the band structure and electrical properties of InAlAs/InGaAs/InAlAs/InP heterostructures containing a composite InGaAs quantum well with InAs and GaAs nanoinserts. From the Shubnikov-de Haas effect, the effective cyclotron mass m _c ^* is determined experimentally and calculated with consideration for the nonparabolicity of the electron energy spectrum. An approach to estimation of the effective mass is proposed and tested. The approach is based on weighted averaging of the m _c ^* of the composite quantum well’s constituent materials. A first proposed heterostructure containing two InAs inserts symmetrically arranged in the quantum well makes a 26% reduction in m _c ^* compared to m _c ^* in the lattice-matched In_0.53Ga_0.47As quantum well possible.     

加速度地震检波器简谐振子有限元分析

介绍简谐振子的工作原理。利用ANSYS软件,采用有限元法创建了简谐振子质量块的实体模型,选择单晶硅作为简谐振子中质量块的材料;设置了模型的材料属性,采用智能分网的方式对模型划分网格,并对质量块模型施加沿x轴水平方向载荷,进行三维的静力分析和模态分析。静力分析得到实体模型的总位移是0.236×10-19μm;模态分析时只对前四阶模型进行了分析,根据其振型图及其总位移的应力云图,得到实体模型的二十阶振动模态的频率是78 001Hz,二十阶的总位移是0.122×10-6μm。     

Effect of growth conditions on incorporation of Si into Ga and As sublattices of GaAs during molecular-beam epitaxy

The effect of dopant concentration and growth-surface crystallographic orientation on the incorporation of Si into Ga and As sublattices was investigated during GaAs molecular-beam epitaxy. The epitaxial layers (epilayers) were grown on GaAs substrates with (100), 2°(100), 4°(100), and 8°(100) orientations at a temperature of 520°C and with (111)A, 2°(111)A, 2°(111)A, 5°(111)A, 6°(111)A, and 8°(111)A (where A = Ga) orientations at a temperature of 480°C. The Sidopant concentration was varied within 10¹⁷–10¹⁹ cm^?3. Through electrical and photoluminescent methods of investigation, the Si impurity was found to occur at the sites of both GaAs-layer sublattices not only as simple donors and acceptors (Si_Ga and Si_As), but also as Si_Ga-Si_As, Si_Ga-V_Ga, and Si_As-V_As complexes. The concentration of Si impurity in various forms depends on the doping level of the layers and on the growth-surface orientation. Amphoteric properties of Si manifest themselves more prominently on the (111)A face than on the (100) one. It is shown that impurity defects form at the stage of layer crystallization and depend on the growth-surface structure.     

Optical Properties of AlGaAs/GaAs Resonant Bragg Structure at the Second Quantum State

Photoluminescence, optical reflectance and electro-reflectance spectroscopies were employed to study an AlGaAs/GaAs multiple-quantum-well based resonant Bragg structure, which was designed to match optical Bragg resonance with the exciton-polariton resonance at the second quantum state in the GaAs quantum wells. The structure with 60 periods of AlGaAs/GaAs quantum wells was grown on a semi-insulating substrate by molecular beam epitaxy. Broad and enhanced optical and electro-reflectance features were observed when the Bragg resonance was tuned to the second quantum state of the GaAs quantum well excitons manifesting an enhancement of the light-matter interaction under double-resonance conditions. By applying an alternating electric field, we revealed electro-reflectance features related to the x(e2-hh2) and x(e2-hh1) excitons. The excitonic transition x(e2-hh1), which is prohibited at zero electric field, was allowed by a DC bias due to brake of symmetry and increased overlap of the electron and hole wave functions caused by electric field.     

An (AlGaAs/GaAs/AlGaAs)<Subscript>60</Subscript> resonant Bragg structure based on the second quantum-confinement level of heavy-hole excitons in quantum wells

Photoluminescence and optical-reflection spectra of a periodic structure consisting of 60 tunneling-isolated GaAs quantum wells separated by AlGaAs barriers are studied. The structure is designed so that, for a certain angle of incidence (∼23°), the Bragg resonance condition is satisfied for light with a photon energy equal to the energy of heavy-hole excitons at the second quantum-confinement level in the wells. It is established experimentally that, under the conditions of double exciton-polariton and Bragg resonance, a superradiant optical mode is formed. Dependences of Bragg and exciton-polariton reflection on the angle of incidence and polarization of light and the temperature are investigated.     

电子元器件失效模式影响分析技术

在元器件中进行失效模式影响分析(FMEA)技术研究和应用的基础上,论述了适合元器件的失效模式、机理影响分析(FMMEA)技术,在国内首次将FMMEA技术应用到元器件的基础上,研制了FMMEA技术分析软件,为元器件的研制和使用中控制或消除相关的失效模式及机理,提高产品质量和可靠性提供了一个新的方法和思路。     

Coupling of electron states in the InAs/GaAs quantum dot molecule

Deep level transient spectroscopy (DLTS) is used to study electron emission from the states in the system of vertically correlated InAs quantum dots in the p-n InAs/GaAs heterostructures, in relation to the thickness of the GaAs spacer between the two layers of InAs quantum dots and to the reverse-bias voltage. It is established that, with the 100 Å GaAs spacer, the InAs/GaAs heterostructure manifests itself as a system of uncoupled quantum dots. The DLTS spectra of such structures exhibit two peaks that are defined by the ground state and the excited state of an individual quantum dot, with energy levels slightly shifted (by 1–2 eV), due to the Stark effect. For the InAs/GaAs heterostructure with two layers of InAs quantum dots separated by the 40 Å GaAs spacer, it is found that the quantum dots are in the molecule-type phase. Hybridization of the electron states of two closely located quantum dots results in the splitting of the levels into bonding and antibonding levels corresponding to the electron ground states and excited states of the 1s ⁺, 1s ^?, 2p ⁺, 2p ^?, and 3d ⁺ types. These states manifest themselves as five peaks in the DLTS spectra. For these quantum states, a large Stark shift of energy levels (10–40 meV) and crossing of the dependences of the energy on the electric field are observed. The structures with vertically correlated quantum dots are grown by molecular beam epitaxy, with self-assembling effects.     

Quantum Hall effect and hopping conductivity in <Emphasis Type="Italic">n</Emphasis>-InGaAs/InAlAs nanoheterostructures

The longitudinal and Hall magnetoresistances are measured in the quantum Hall effect regime in the n-InGaAs/InAlAs heterostructures at temperatures of T = (1.8–30) K in magnetic fields up to B = 9 T. Temperature-induced transport in the region of the longitudinal resistance minima, corresponding to the plateau regions at Hall resistance, is investigated within the framework of the concept of hopping conductivity in a strongly localized electron system. The analysis of variable-range hopping conductivity in the region of the second, third, and fourth plateau of the quantum Hall effect provides the possibility of determining the localization length exponent.     

全光混沌序列发生器设计

如何在光域产生混沌序列并将其作为光码分多址OCDMA(optical code division multiple access)系统的地址码,是近年来一个新的研究方向。利用马赫-增德尔干涉仪设计了一种完全在光域产生模拟双极性混沌序列的发生器。通过控制马赫-增德尔干涉仪两臂引起的相移来调制输入光电场的振幅和相位,使得输出光电场矢量等于输入光电场矢量与余弦项的乘积,多个干涉仪及光纤延迟线和相移器可以构成混沌序列发生器,并按logistic映射在光域产生双极性混沌序列。此混沌序列发生器可作为OCDMA系统的编解码器,提高保密性并增加系统可容纳的用户数。