Selective etching characteristics of HF for AlxGa1-xAs/GaAs

The first detailed report of the selective etching characteristics of an AlxGa1-xAs/GaAs DH wafer (x?0.4) in an HF system is given. Selective etching at a cleaved facet and a calculation of the energy of activation are included.     

GaAs/Al_xGa_(1-x)As超晶格中的纵光学声子模(英文)

The long wavelength optical phonon spectra of AlxGa1-xAs mixed crystals appear as "two-mode" behaviour, i.e. there are GaAs-like and AlAs-like optical branches simultaneously. Besides* the LO phonon dispersion curves of bulk GaAs and GaAs-like in AlxGa1-xAs mixed crystal are partly overlapped. Therefore, we expect, in GaAs/AlxGa1-xAs superlattices, that LO phonons are partly in confined modes while partly in folded one, and that AlAs-like modes are confined in AlxGa1-xAs layers.The samples of GaAs/AlxGa1-xAs superlattices were grown by MBE on (001) oriented semi-insulating GaAs substrates. Raman spectra were measured in the back-scattering geometry at room temperature. Only odd modes with B2 symmetry were observed for LO modes confined in the GaAs layer. This result is in agreement with the previous reports. In addition, AlAs-like LO modes confined in AlxGa1-xAs layers were observed for the first time.     

分子束外延生长的GaAs-Al_xGa_(1-x)As多层异质结构中的“精细低维调制条纹”的观察

应用透射式电子显微镜观察了GaAs-Al_xGa_(1-x)As多层异质结结构中的“精细低维调制条纹”。在邻近GaAs-Al_xGa_(1-x)As超晶格层的缓冲层中和与这缓冲层邻近的GaAs-Al_xGa_(1-x)As超晶格层的小区域中发现了等宽度的“精细低维调制条纹”,其宽度为9.1(?)的GaAs条纹,12(?)的Al_xGa_(1-x)As条纹。文中介绍了用显微密度计获得的这些条纹的密度分布结果。同时还给出了GaAs-Al_xGa_(1-x)As 多层异质结结构的晶格像和用X射线能量散射谱技术获得的成分定量分析结果。     

Cathodoluminescence study of pyramidal facets in piezoelectric InGaAs/GaAs multiple quantum well pin photodiodes

A study of the optical and electrical activity of defects at the surface of InGaAs/GaAs multiple quantum well pin photodiodes was done on two different misoriented (111)B GaAs substrates: substrate A, misoriented 1° towards [2̄11] and substrate B, misoriented 2° towards [21̄1̄]. In this article, we report the existence of different faceted defects at the surface with the misorientation and their influence on the optical performance. The surface of photodiodes grown on substrate A shows inclined pyramids with two enhanced facets. The electron beam induced current measurements showed that these pyramids act as high efficient collector of the e-beam excited electron–hole pairs (e–h). This behaviour agrees with the reduction of the cathodoluminescence emission efficiency at the facets. In contrast, a different pyramid type with one enhanced facet is observed at the surface of diodes grown on substrate B. However, these facets have not shown either optic or electric activity. In these diodes, the dislocations localised at the active region degrade the device performance acting as non-radiative recombination centres.     

GaAs表面及Al_xGa_（1－x）As／GaAsHBT外基区表面（NH_4）_2S／SiN_x钝化工艺研究

分析了ＡｌｘＧａ１－ｘＡｓ／ＧａＡｓＨＢＴ外基区表面复合电流及外基区表面复合速度对直流增益的影响，用光致发光（ＰＬ）谱和Ａｌ／ＳｉＮｘ－Ｓ／ＧａＡｓＭＩＳ结构Ｃ－Ｖ特性，研究了ＧａＡｓ表面（ＮＨ４）２Ｓ／ＳｉＮｘ钝化工艺的效果及其稳定性。结果表明，ＥＣＲ－ＣＶＤ淀积ＳｉＮｘ覆盖并在Ｎ２气氛中退火有助于改善ＧａＡｓ表面硫钝化效果的稳定性。在此基础上形成了一套包括（ＮＨ４）２Ｓ处理、ＳｉＮｘＥＣＲ－ＣＶＤ淀积及退火并与现有ＨＢＴ工艺兼容的外基区表面钝化工艺，使发射区面积为４×１０μｍ２的器件增益比钝化前提高了４倍，且６０天内不退化。     

分子束外延生长Al_xGa_(1-x)As/GaAs超晶格及结构、光学特性研究

报道了分子束外延生长80个周期的Al_xGa_(1-x)As/GaAs超晶格,X射线衍射和透射电镜的结果表明超晶格样品有良好的结构特性,光反射光谱观察到阱内的电子跃迁过程,其结果与理论计算相符。     

三组三元合金异质结的价带带阶

采用基于LMTO－ASA的平均键能计算方法和原子集团展开方法，研究了三组典型的晶格匹配三元合金异质结（GaAs）x（Ge2）1-x／GaAs，（AlAs）x（Ge2）1-x／GaAs和AlxGa1-xAs／GaAs的价带带阶△Ev（x）值。研究表明：AlxGa1-xAs／GaAs异质结的Mv（x）值随合金组分x的变化接近于线性；（GaAs）x（Ge2）1-x／GaAs和（AlAs）x（Ge2）1-x／GaAs的△Ev（x）值随合金组分x的变化是非线性的。△Ev（x）的理论计算值与实验结果相当符合。     

GaAs/Al_xGa_(1-x)As量子阱红外探测器光谱特性的研究

采用MBE法制备了不同结构参数及不同阱中掺杂浓度的GaAs/AlxGa1-xAs量子阱红外探测器外延材料。通过对量子阱红外探测器材料特性和器件特性的实验测试及理论分析,研究了量子阱红外探测器的响应光谱特性,并通过薛定谔方程和泊松方程的求解,对掺杂对量子阱能级的影响做了研究。结果表明,由于应力导致的能带非抛物线性使得阱中能级发生了变化,从而引起吸收峰向高能方向发生了漂移,而阱中进行适度的掺杂没有对量子阱能级造成影响,光致发光谱实验结果与之吻合较好。在光电流谱的实验分析基础之上,分析了量子阱阱宽、Al组分与峰值探测波长λ的关系,为量子阱红外探测器的设计优化提供了参考。     

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。     

Formation of uniform GaAs multi-atomic steps with 20–30 nm periodicity and related structures on vicinal (111)B planes by MBE

We studied morphology of GaAs surfaces and the transport properties of two-dimensional electron gas (2DEG) on vicinal (111)B planes. Multi-atomic steps (MASs) are found on the vicinal (111)B facet grown by molecular beam epitaxy, which will affect electron transport on the facet. We also studied how the morphology of GaAs epilayers on vicinal (111)B substrates depends on growth conditions, especially on the As₄ flux. The uniformity of MASs on the substrates have been improved and smooth surfaces were obtained when the GaAs was grown with high As₄ flux, providing step periodicity of 20 nm. The channel resistance of the 2DEG perpendicular to the MASs is reduced drastically with this smooth morphology. These findings are valuable not only for fabricating quantum devices on the (111)B facets but also those on the vicinal (111)B substrates.     

二维电子气简介

本文简要介绍了液氦表面、半导体表面空间电荷层和化合物半导体异质结界面的二维电子气.积累在选择掺杂GaAs/Al_xGa_(1-x)A_s异质结界面的二维电子气在低温下迁移率剧增.调制掺杂GaAs/Al_xGa_(1-x)A_s超晶格是一个适合于研究量子态和次带能级的系统.因而,异质结界面处二维电子气的研究,不仅可能为新的高速和微波器件的探索打开新的途径,而且还提供了研究量子效应的新领域.     

长波双色Al_xGa_(1-x)As/GaAs量子阱红外探测器的研制

介绍了长波双色AlxGa1-xAs/GaAs多量子阱红外探测器单元的设计、制作和测试。器件光敏面面积为300μm×300μm,光吸收峰值波长分别为10.8、11.6μm;采用垂直入射光耦合的工作模式,65K温度2V偏压下,两个多量子阱区的暗电流分别为4.23×10-6、4.19×10-6A;黑体探测率分别为1.5×109、6.7×109cm.Hz1/2/W;响应率分别为0.063、0.282A/W。GaAs基量子阱红外探测器(QWIP)材料生长和加工工艺成熟、大面积均匀性好、成本低、不同波段之间的光学串音小,使得AlGaAs/GaAsQWIP在制作多色大面阵方面具有明显的优势。     

Al_xGa_(1-x)As/GaAs LOC激光器中的深能级

本文采用深能级瞬态谱(DLTS)方法,测量了A1_xGa_(1-x)As/GaAs LOC(Large Optical Cavity)激光器中的深中心,并初步分析了这些深中心与Al含量的关系,以及对器件退化的影响。     

Spatially resolved Raman investigation of Si-doped GaAs layers on patterned GaAs(100) substrates grown by molecular beam epitaxy

Local carrier transport properties of Si-doped GaAs layers on ridge structures exhibiting (111)A and (111)B sidewalls are investigated. The layers were grown by molecular beam epitaxy at different substrate temperatures and As/Ga flux ratios. Using spatially resolved Raman spectroscopy we determine the type and density of free charge carriers (≥ 5 × 10¹⁷ cm⁻³) in the grown layers on the different index facets from an analysis of the coupled plasmon-longitudinal optical-phonon mode which was calibrated against Hall standards. We demonstrate that on the (100) and (111)B facets the regrown layers are n-type and on the (111)A facets p- or n-type depending on the growth conditions. Line scans of the carrier density show that the (100)/(111)A/(100) facet transition forms a graded lateral n-p-n junction. Spatially resolved photoluminescence measurements confirm our findings.     

Submilliampere lasing of Zn-diffused mesa buried-hetero AlxGa1-xAs/GaAs multi-quantum-well lasers at 77 K

Extremely low-threshold semiconductor lasers were fabricated by forming Zn-diffused mesa buried-hetero (DMB) structures from low-pressure MOCVD-grown AlxGa1-xAs/GaAs multi-quantum-well, separate-confinement heterostructure wafers. CW threshold currents as low as 880 ?A at 77 K and 2.4 mA at room temperature were obtained for a 100 ?m-long device.     

超晶格(Al_xGa_(1-x)As)_m/(GaAs)_m(110)的电子能带结构

采用紧束缚的重整化方法计算了超晶格(Al_xGa_1 xAs)_m/(GaAs)_m(110)的电子能带结构(1≤m≤10)。讨论了电子能带结构随超晶格层厚m及合金组分x的变化情况。计算结果表明,对于不同的合金组分x,超晶格可以处在三个不同区域:A区,直接能隙结构,Ⅰ-型超晶格;B区,间接能隙结构,Ⅰ-型超晶格;C区,间接能隙结构,Ⅱ—型超晶格。     

GaAs/AlGaAs量子阱隧道电流的压力效应

本文使用单带双谷模型计算了通过AlGaAs势垒的隧道电流的压力系数.计算中考虑了能谷的非抛物线性,Г,X两个能谷的贡献以及电场的作用,说明了电流压力系数随电场增强而下降以及大压强下隧道电流对数偏离线性的实验现象.在此基础上进一步研究了加压GaAs/AlAs量子阱隧道电流中的Г-X混和效应.     

HEMT太赫兹探测器的二维电子气特性分析

采用分子束外延技术(MBE)对GaAs/Al_xGa_(1-x)As二维电子气(2DEG)样品进行了制备,样品制备过程中,通过改变Al的组分含量、隔离层厚度、对比体掺杂与δ掺杂两种方式,在300 K条件下对制备的样品进行了霍尔测试,获得了室温迁移率7.205E3cm~2/Vs,载流子浓度为1.787E12/cm~3的GaAs/Al_xGa_(1-x)As二维电子气沟道结构,并采用Mathematica软件分别计算了不同沟道宽度时300 K、77 K温度下GaAs基HEMT结构的太赫兹探测响应率,为HEMT场效应管太赫兹探测器的研究和制备提供了参考依据.     

量子点场效应单光子探测器二维电子气电子迁移率分析

设计了一种基于场效应晶体管的量子点场效应单光子探测器,利用二维弛豫时间的近似理论建立了二维电子气电子迁移率的散射模型,通过求解量子点场效应单光子探测器GaAs/AlxGa1-xAs二维电子气系统电子和声子相互作用的Hamiltonian函数,得到了不同温度、不同Al组分以及不同二维电子气电子面密度条件下晶格振动散射对探测器二维电子气电子迁移率的影响.仿真结果显示,提高二维电子气的电子面密度浓度和适当增大Al组分,并降低工作温度,有助于探测器获得更高的二维电子气电子迁移率.     

Al_xGa_(1-x)As/GaAsCSP可见光单模激光器

近0.78μm可见光单模激光器在光盘技术,包括视频盘、PCM声频盘和光盘存贮器、激光束高速打印、销售点(POS)终端等信息终端装置中有着广泛的应用前景。特别是打印机和小型光盘应用量大而广。另外,用近可见光单模LDs及其列阵作光源泵浦Nd:YAG激光器和1.06μm单模光纤放大器又是新近国内外十分热门的课题。因此,研制和生产可见光半导体单模激光器,有较大经济效益和发展前景。 本文报道用800℃下液相外延技术研制成稳定基横模、单纵模工作的Al_xGa_(1-x)As/GaAsCSP可见光(λ～779.0nm)单模LDs及其主要性能。