新型微光成像器件及应用

采用全固态微光成像器件是未来微光成像的发展趋势。介绍了2种全固态微光器件 EMCCD、InxGa1－xAs,分析了其成像性能,描述了其研究现状,对比了传统的真空光电成像与全固态微光成像性能指标,阐明了微光成像器件向着高灵敏度、低噪声、宽光谱响应和强适应能力方向发展。     

势垒高度对GaAs/AlxGa1-xAs QWIP光谱特性的影响

为了确定束缚态到准束缚态工作模式QWIP响应波长与势垒高度关系,采用金属有机物化学气相沉积法生长制备势垒高度不同GaAs/AlxGa1-xAs QWIP样品,采用傅里叶光谱仪对样品进行77 K液氮温度光谱测试。结果显示1#,2#样品峰值响应波长与据薛定谔方程得到峰值波长误差为15.6%,4.6%。结果表明:引起量子阱中子带间距离逐渐扩大与峰值响应波长蓝移的根本原因是势垒高度的增加。高分辨透射扫描电镜实验结果表明量子阱材料生长过程精度控制不够及AlGaAs与GaAs晶格不匹配是造成1#样品误差较大的主要原因。说明调节势垒高度可实现QWIP峰值波长微调的目的。     

DX全固态中波发射机调制系统数字化

本文简要阐述了基于可编程逻辑器件的DX全固态发射机调制系统数字化项目的目标和基本功能。这个项目符合当前我国广播电视系统数字化的大趋势,可以明显提升发射机系统的稳定性和电声指标。使用可编程逻辑器件作为系统的核心处理部分可以更好的提高系统的集成度和灵活性,满足更多的设计要求。     

高品质三元CdxPb1-xSe量子点的制备与非线性光学性能研究

因为具有独特的量子效应,量子点一直受到诸多领域的广泛关注。为了研究CdxPb1-xSe三元量子点非线性特性,研究了高品质三元量子点的简便制备方法,在此基础上,进一步在532nm激光条件下利用Z-扫描技术研究了其非线性光学性能。结果表明,以制备的N-油酰基-吗啡啉为溶剂,采用改进一锅煮法成功地获得了大小均一、结晶良好的CdxPb1-xSe量子点;Cd0.5Pb0.5Se量子点的非线性吸收系数和非线性折射率分别为1.0110-9m/W和-1.110-10 esu,相比于CdSe二元量子点,体现出更加显著的非线性折射特性。因此,CdxPb1-xSe量子点在激光防护、光电开关等方面具有重要的潜在应用价值。     

88 nm栅长fmax＝201 GHz InP基In0.53Ga0.47As/In0.52Al0.48As HEMT器件

我们成功研制了栅长88 nm, 栅宽2 50 μm, 源漏间距为2.4 μm 的InP基In0.53Ga0.47As/In0.52Al0.48As高电子迁移率器件(HEMT)。栅是使用PMMA/Al/UVⅢ,通过优化电子束曝光时间及其显影时间的方式制作的。这些器件有比较好的直流及其射频特性：峰值跨导、最大源漏饱和电流密度、开启电压、ft和fmax 分别为765 mS/mm, 591 mA/mm, -0.5 V, 150 GHz 和201 GHz。这些器件将非常适合于毫米波段集成电路。     

衬底温度和生长速率对MBE自组织生长InxGa1-xAs/GaAs QD的影响

研究GaAs基InxGa1-xAs/GaAs量子点(QD)的MBE生长条件,发现在一定的Ⅴ/Ⅲ比下,衬底温度和生长速率是影响InxGa1-xAs/GaAsQD形成及形状的一对重要因素,其中衬底温度直接影响着In的偏析程度,决定了InxGa1-xAs/GaAs的生长模式;生长速率影响着InxGa1-xAs外延层的质量,决定了InxGa1-xAs/GaAsQD的形状及尺寸.通过调节衬底温度和生长速率生长出了形状规则、尺寸较均匀的InxGa1-xAs/GaAsQD(x＝0.3).     

闪锌矿BxAl1-xAs合金的LP-MOCVD生长研究

利用低压金属有机化学气相沉积(LP-MOCVD)生长工艺,采用三乙基硼(TEB)源,在GaAs(001)衬底上生长了B并入比为0.4%～4.4%的一系列BxAl1-xAs合金。实验结果表明,BxAl1-xAs的最优生长温度为580℃;当生长温度为550℃和610℃时,BxAl1-xAs中B并入比都会下降,550℃时B并入比下降更为显著。在580℃最优生长温度下,B并入比随着TEB摩尔流量增加而提高,且B并入比从临界值2.1%增加至最大值4.4%时,DCXRDω-2θ扫描BxAl1-xAs衍射峰的半高宽值从51.8 arcsec升高到204.7 arcsec,原子力显微镜(AFM)测试表面粗糙度从2.469 nm增大到29.086 nm,说明B并入比超过临界值后BxAl1-xAs晶体质量已经逐渐严重恶化。     

DPSA双极器件中的1/f噪声特性研究

在现代高性能模拟集成电路设计中,噪声水平是影响电路性能的关键因素之一.研究了双多晶自对准高速互补双极NPN器件中发射板结构对器件直流和低频噪声性能的影响.实验结果表明,多晶硅发射极与单晶硅界面超薄氧化层以及发射极几何结构是影响多晶硅发射极双极器件噪声性能的主要因素.     

基于Si/Si1-xGex/Si HBT的微波功率器件Ge组分的数值拟合计算

采用异质结双台面双极型结构设计微波功率器件,选择Si作发射区和集电区,Si1-xGex合金作基区的n—p—n型HBT,利用数学方法,通过实验数据,采用MATLAB得到了一个比线性化更精确的禁带宽度Eg在300K时关于Ge组分变化的方程。并用数值方法计算出集电区电流密度Jc随VBE变化的直流方程,与实验结果相符。并得到一个最佳的Ge组分值。对器件的仿真设计具有实际指导意义。     

声表面波器件用Pb[(Mn_(1/3)Nb_(2/3))_xZr_yTi_(1-x-y)]O_3压电陶瓷材料的研制

声表面波器件用铌锰锆钛酸铅系压电陶瓷材料,采用真空烧结工艺来提高陶瓷致密度,改善表面光洁度。添加CeO_2抑制晶粒生长,制得了小于2μm微晶压电陶瓷材料。进一步改善陶瓷材料的表面光洁度,样品经抛光后得表面最大孔洞小于0.5μm,适宜制作38MHz的声表面波滤波器件。     

Investigation of graded InxGa1−xP buffer by Raman scattering method

The compositional changes of In_xGa_1−xP graded buffer inserted between GaP substrate and subsequently grown In_0.36Ga_0.64P homojunction LED structure were investigated by Raman spectroscopy. The indium content of In_xGa_1−xP interlayers was increased in eight steps with thickness of 300 nm and constant compositional change Δx_In between the steps. The properties of In_xGa_1−xP graded buffer along the structure cross-section have been studied by Raman back scattering method and the changes in GaP LO and TO phonons were investigated. Raman shift of 13 cm⁻¹ in GaP-like LO₁ phonon was measured on beveled [100]surface for compositional change of In_xGa_1−xP layer in the range of 0<x_In<0.32. The measurements on the cleaved edge of the sample in [011] direction revealed a strong TO phonon at 366 cm⁻¹ and weak LO phonon peak at 405 cm⁻¹ in GaP substrate. By reaching the graded In_xGa_1−xP region the intensity of TO phonon decreases and appearance of considerable TO₁ phonon shift up to 350 cm⁻¹ for In content x_In=0.16 was observed. For upper graded layers with x_In from 0.16 to 0.24 the position of GaP-like TO₁ was constant and can be ascribed to relaxation of lattice mismatched thin In_xGa_1−xP graded upper layers in the structure.     

Anomalous light sensitivity of organometallic VPE AlxGa1−xAs

The capacitance of Al_0.3Ga_0.7As p-n junctions grown by organometallic vapor phase epitaxy at 690°C with V/III flux ratio of ～20 is found to be extremely light-sensitive. The light sensitivity is shown to be caused by the presence of two dominant hole traps having energy levels at 0.87 and 0.74 eV above the valence band. The traps were studied by three different schemes of DLTS measurements. The traps could be annealed out by post-growth annealing at 650°C for 1 hr in a hydrogen atmosphere.     

High performance Al0.35Ga0.65As/GaAs HBT's

AlGaAs emitter heterojunction bipolar transistors (HBTs) are demonstrated to have excellent dc and RF properties comparable to InGaP/GaAs HBTs by increasing the Al composition. Al_0.35Ga _0.65As/GaAs HBTs exhibit very high dc current gain at all bias levels, exceeding 140 at 25 A/cm² and reaching a maximum of 210 at 26 kA/cm² (L=1.4 μm×3 μm, R_sb=330 Ω/□). The temperature dependence of the peak dc current gain is also significantly improved by increasing the AlGaAs mole fraction of the emitter. Device analysis suggests that a larger emitter energy gap contributes to the improved device performance by both lowering space charge recombination and increasing the barrier to reverse hole injection     

Modeling of short-pulse threshold voltage shifts due to DX centersin AlxGa1-xAs/GaAs and AlxGa1-xAs/InyGa1-yAs MODFET's

The DX-center-related short-pulse threshold voltage shifts (SPTVS) in Al_xGa_1-xAs-based MODFETs is modeled using CBAND, a simulator that solves Poisson equations self-consistently with Schrodinger equations and donor statistics. Using values given in the literature for the DX energy level in Al_xGa_1-xAs this technique gives good agreement between measured and simulated SPTVS for Al_0.3Ga_0.7As/GaAs and Al_0.3Ga_0.7As/In_0.2Ga_0.8As MODFETs. Both simulation and experiment show that the use of Al_0.2 Ga_0.8As in the donor layer reduces the SPTVS relative to the structures using Al_0.3Ga_0.7As. However, the measured shifts at this composition are considerably lower than the simulated values, indicating a DX energy level that may be higher than the value extrapolated from the literature, possibly due to the existence of multiple trap levels. Despite this discrepancy, these results support the use of strained-channel layers and lower Al_x Ga_1-xAs compositions in MODFETs for digital and other large-signal applications requiring good threshold stability     

Quantum-well Hall devices in Si-delta-dopedAl0.25Ga0.75As/GaAs and pseudomorphic Al0.25Ga0.75As/In0.25Ga0.75As/GaAsheterostructures grown by LP-MOCVD: performance comparisons

Characterized herein are quantum-well Hall devices in Si-delta-doped Al_0.25Ga_0.75As/GaAs and pseudomorphic Al_0.25Ga_0.75As/In_0.25Ga _0.75As/GaAs heterostructures, grown by low-pressure metal organic chemical vapor deposition method. The Si-delta-doping technique has been applied to quantum-well Hall devices for the first time. As a result high electron mobilities of 8100 cm^-2/V·s with a sheet electron density of 1.5×10¹² cm^-2 in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As/GaAs structure and of 6000 cm^-2/V·s with the sheet electron density of 1.2×10¹² cm^-2 in Al_0.25Ga_0.75As/GaAs structure have been achieved at room temperature, respectively. From Hall devices in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As structure, the product sensitivity of 420 V/AT with temperature coefficient of -0.015 %/K has been obtained. This temperature characteristic is one of the best result reported. Additionally, a high signal-to-noise ratio corresponding to the minimum detectable magnetic field of 45 nT at 1 kHz and 75 nT at 100 Hz has been attained. These resolutions are among the best reported results     

60-GHz noise performance of ion-implanted InxGa1-xAs MESFET's

The authors report the 60-GHz noise performance of low-noise ion-implanted In_xGa_1-xAs MESFETs with 0.25 μm T-shaped gates and amplifiers using these devices. The device noise figure was 2.8 dB with an associated gain of 5.6 dB at 60 GHz. A hybrid two-state amplifier using these ion-implanted In_xGa_1-x As MESFETs achieved a noise figure of 4.6 dB with an associated gain of 10.1 dB at 60 GHz. When this amplifier was biased at 100% I _dss, it achieved 11.5-dB gain at 60 GHz. These results, achieved using low-cost ion-implantation techniques, are the best reported noise figures for ion-implanted MESFETs     

Strained layer InxGa1-xAs/GaAs and InxGa1-xAs/InyGa1-yPmultiple-quantum-well optical modulators grown by gas-source MBE

The first results on low-power p-i-n diode modulator structures using strained multiple quantum wells (MQW's) of InGaAs/InGaP grown by gas-source molecular beam epitaxy (MBE) on GaAs are presented. A comparison of transmission, reflection, and photocurrent spectra for these nonresonant devices with those fabricated from InGaAs/GaAs indicates larger modulation, with a maximum change in reflection of >42% observed at 5-V bias at a wavelength of 0.96 μm     

Grown junction GaAs solar cells with a thin graded band-gap AlxGa1−xAs surface layer

Liquid phase epitaxial growth techniques were used to fabricate (n)GaAs:Sn-(p)GaAs:Ge-(p)Al_xGa_1?xAs:Ge heterostructure solar cells. Graded band-gap Al_xGa_1?xAs layers with thicknesses between 1500 and 2500 Å were prepared by isothermal growth from an undersaturated solution. Spectral response measurements show that the resulting built-in electric field at the surface of the solar cell reduces the surface recombination velocity and improves the collection efficiency.     

Short pulse transfer characteristics of AlxGa1-xAs/GaAs andAlxGa1-xAs/InyGa1-yAsmodulation-doped heterojunction FET's

Short-pulse drain current versus gate voltage transfer characteristics measured for modulation-doped HFETs (MODFETs) with four donor-layer-channel-layer combinations-(1) Al_0.3Ga_0.7 As-GaAs, (2) Al_0.2Ga_0.8As-GaAs, (3) Al_0.3Ga_0.7As-In_0.2Ga_0.8As, and (4) Al_0.2Ga_0.8As-In_0.2 a_0.8 As-are compared with the DC transfer characteristics. The measurements are relevant to high-speed switching in HFET circuits. Significant shifts in threshold voltage are observed between the DC and short-pulse characteristics for the structures with n⁺-Al_0.3Ga_0.7As donor layers, while the corresponding shifts for structures with n⁺-Al_0.2Ga_0.8As donor layers are relatively small or virtually nonexistent     

微微秒Al_xGa_(1-x)As双异质结激光器

用宽度为300微微秒的电脉冲驱动质子轰击条形的Al_xGa_(1-x)As双异质结激光器,产生12微微秒光脉冲。并已经用来检测快速光电二极管的响应速率。