用1553nm激光脉冲触发GaAs光电导开关的研究

用1553nm飞秒光纤激光器触发半绝缘GaAs光电导开关的实验表明,当光电导开关处于3.33～10.3kV/cm的直流偏置电场并被脉冲宽度200fs且单脉冲能量0.2nJ的激光脉冲照射时,开关表现为线性工作模式,开关输出峰值电压为0.8mV.分析表明,开关对波长为1553nm触发激光脉冲表现出的弱光电导现象起因于半绝缘GaAs材料EL2深能级的作用.     

用1064nm激光脉冲触发半绝缘GaAs光电导开关的奇特光电导现象

报道了用1064nm激光脉冲触发半绝缘GaAs光电导开关的一种奇特光电导现象.GaAs光电导开关的电极间隙为4mm,当偏置电场分别为2.0和6.0kV/cm时,用脉冲能量为0.8mJ,宽度为5ns的激光触发开关,观察到开关输出的线性和非线性工作模式.当偏置电场增至9.5kV/cm,触发光脉冲能量在0.5～1.0mJ范围时,观察到奇特的光电导现象,开关先输出一个线性电脉冲,经过大约20～250ns时间延迟后,触发光脉冲消失,开关又输出一个非线性电脉冲.这一奇特光电导现象的物理机制与半绝缘GaAs中的反位缺陷和吸收机制有关.分析计算了线性与非线性电脉冲之间的延迟时间,结果与实验观察基本吻合.     

Analysis of Damage Induced by Repetition-Frequency Optical Pulse in Semi-insulating GaAs PCSS's Material

通过波长为1064 nm的重频激光光脉冲触发半绝缘GaAs光导开关损伤测试实验,观察脉冲激光触发过程中光电导开关电阻率的变化,对比低重频(＜1 kHz)和高重频的激光脉冲对GaAs光电导开关芯片的损伤阈值,分析了不同重复频率的激光脉冲引起光导开关芯片材料光损伤的主要原因,并探讨了损伤机理.研究表明,在重复频率激光作用下GaAs光导开关芯片材料的破坏阈值比在单脉冲作用下低,且不同重复频率的激光辐照下材料表面的温升速率不同.当激励光脉冲重复频率较低(＜1 kHz)时,芯片内的温升效应不显著,此时光损伤与重复频率无明显依赖关系,主要损伤机制为微损伤累积;而当重复频率较高时,开关材料内热积累引起的损伤占主要地位.     

重频光脉冲对半绝缘GaAs光导开关损伤分析

通过波长为1 064 nm的重频激光光脉冲触发半绝缘GaAs光导开关损伤测试实验,观察脉冲激光触发过程中光电导开关电阻率的变化,对比低重频(1 kHz)和高重频的激光脉冲对GaAs光电导开关芯片的损伤阈值,分析了不同重复频率的激光脉冲引起光导开关芯片材料光损伤的主要原因,并探讨了损伤机理。研究表明,在重复频率激光作用下GaAs光导开关芯片材料的破坏阈值比在单脉冲作用下低,且不同重复频率的激光辐照下材料表面的温升速率不同。当激励光脉冲重复频率较低(1 kHz)时,芯片内的温升效应不显著,此时光损伤与重复频率无明显依赖关系,主要损伤机制为微损伤累积;而当重复频率较高时,开关材料内热积累引起的损伤占主要地位。     

用飞秒激光触发GaAs光电导体产生THz电磁波的研究

报道了用半绝缘GaAs材料研制的光电导偶极天线在飞秒激光脉冲触发下辐射THz电磁波的实验结果.GaAs光电导偶极芯片的两个欧姆接触电极间隙为3mm,采用Si3N4薄膜绝缘保护,在540V直流偏置下被波长800nm,脉宽14fs,重复频率75MHz,平均功率130mW的飞秒激光脉冲触发时产生THz电磁波.用电光取样测量得到了THz电磁脉冲的时域波形和频谱分布.THz电磁波的辐射峰值位于0.5THz左右,频谱宽度大于2THz,脉冲宽度约为1ps.     

用飞秒激光触发GaAs光电导体产生THz电磁波的研究

报道了用半绝缘GaAs材料研制的光电导偶极天线在飞秒激光脉冲触发下辐射THz电磁波的实验结果.GaAs光电导偶极芯片的两个欧姆接触电极间隙为3mm,采用Si3N4薄膜绝缘保护,在540V直流偏置下被波长800nm,脉宽14fs,重复频率75MHz,平均功率130mW的飞秒激光脉冲触发时产生THz电磁波.用电光取样测量得到了THz电磁脉冲的时域波形和频谱分布.THz电磁波的辐射峰值位于0.5THz左右,频谱宽度大于2THz,脉冲宽度约为1ps.     

半绝缘GaAs光电导开关的击穿特性

研究了在不同触发条件下半绝缘GaAs光电导开关的击穿特性.当触发光能量和偏置电场不同时,半绝缘GaAs光电导开关的击穿损坏程度也不同,分别表现为完全击穿、不完全击穿和可恢复击穿三种类型.通过对击穿实验结果的分析认为,电子俘获击穿机制是导致半绝缘GaAs光电导开关击穿损坏的主要原因.偏置电场和陷阱电荷所产生热电子的数量和动能决定了Ga-As键的断裂程度,Ga-As键的断裂程度则反映半绝缘GaAs光电导开关的击穿类型.     

半绝缘GaAs光电导开关的击穿特性

研究了在不同触发条件下半绝缘GaAs光电导开关的击穿特性 .当触发光能量和偏置电场不同时 ,半绝缘GaAs光电导开关的击穿损坏程度也不同 ,分别表现为完全击穿、不完全击穿和可恢复击穿三种类型 .通过对击穿实验结果的分析认为 ,电子俘获击穿机制是导致半绝缘GaAs光电导开关击穿损坏的主要原因 .偏置电场和陷阱电荷所产生热电子的数量和动能决定了Ga—As键的断裂程度 ,Ga—As键的断裂程度则反映半绝缘GaAs光电导开关的击穿类型     

半绝缘GaAs光电导开关亚皮秒传输特性的研究

 本文应用Ensemble-Monte Carlo方法模拟了半绝缘GaAs(SI-GaAs)光电导开关基于Auston等效电路亚皮秒传输特性.从载流子在开关体内的动态特性出发,研究了光电导开关在飞秒激光脉冲触发下光电导传输特性、电介质弛豫特性、开关储能特性以及开关工作模式;分析了非线性光电导开关对光能阈值和偏置电场阈值要求的物理机制.     

大功率超快半导体光电导开关的触发瞬态特性

报道了用ns和fs超快脉冲激光器触发GaAs光电导开关的实验结果.用μJ量级的ns光脉冲触发3mm间隙的GaAs光电导开关,观察到线性和非线性工作模式,峰值电流达560A.当用重复率为76MHz的fs激光脉冲串触发同一器件时,电流脉冲上升时间小于200ps.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-