MBE[(AI_xGa_(1-x)As)_l(GaAs)_m_n/GaAs(001)超晶格结构参数的X射线双晶衍射测量研究

本文根据超晶格结构的台阶模型,利用X射线衍射的运动学模型,导出了超晶格的X射线衍射峰的相对光强比.利用X射线双晶衍射方法测定了MBE[(Al_xGa_(1-x)As)_1(GaAs)_m]./GaAs(001)一维超晶格的衍射迴摆曲线,除超晶格的主衍射峰外,还观察到一级和二级卫星峰.由这些衍射峰之间的角距离和相对光强比,计算出了超晶格的结构参数,其中包括周期D、垒宽L_B、量子阱宽度L_Z和Al含量x值.     

MBE[(AI_xGa_(1-x)As)_l(GaAs)_m]_n/GaAs(001)超晶格结构参数的X射线双晶衍射测量研究

本文根据超晶格结构的台阶模型,利用X射线衍射的运动学模型,导出了超晶格的X射线衍射峰的相对光强比.利用X射线双晶衍射方法测定了MBE[(Al_xGa_(1-x)As)_1(GaAs)_m]./GaAs(001)一维超晶格的衍射迴摆曲线,除超晶格的主衍射峰外,还观察到一级和二级卫星峰.由这些衍射峰之间的角距离和相对光强比,计算出了超晶格的结构参数,其中包括周期D、垒宽L_B、量子阱宽度L_Z和Al含量x值.     

应变和成份调制超晶格的CBED研究

由A晶格和B晶格超薄层构成一维周期性结构称为超晶格。根据超晶格中应变量的大小可对超晶格进行分类,当应变量很小,各层的原子散射振幅相差甚远时,则为成份调制的超晶格,如AlAs/GaAs超晶格:若应变量显著,而各层的原子散射振幅相差不大时,则为也变调制的超晶恪,如In_xGa_(1-x)As/GaAs超晶格。最近我们用会聚束电子衍射(CBED)研究了成份调制的超晶格AlAs/GaAs和应变调制的超晶格In、Ga_(1-x)As/GaAs的运动学和动力学衍射效应。     

半导体超晶格结构参数的x射线衍射运动学理论拟合计算

运用x射线衍射的运动学理论研究了[(Ga_(1-x)Al_xAs)_m(GaAs)_a]_N/GaAs(001)一维超晶格结构。通过模拟计算,精确确定了起晶格的结构参数。本文所述的方法可用于各种超晶格结构,具有普遍意义。另外,还对超晶格卫星峰强度的非对称性以及界面过渡层的存在对卫星峰强度的影响,做了必要的讨论。     

弹性应变及结构参数对InAs/GaAs应变层超晶格能带结构的影响

本文报道弹性应变及结构参数对 InAs/GaAs应变层超晶格导带、价带不连续性及其子能带结构的影响.通过分析流体静应力和单轴应力对体材料带边能带位置的影响,确定了 InAs/GaAs超晶格导带及价带能量不连续性,并用包络函数法计算了该超晶格的子能带结构.结果表明:这些量不仅依赖于组成超晶格的两种材料的体性质,而且还依赖于超晶格的晶格常数,势阱、势垒宽度以及材料的应变;通过调节InAs层与 GaAs层的层厚之比,可以使 InAs/GaAs超晶格价带轻空穴处于第Ⅱ类超晶格势当中,从而实现轻空穴与电子、重空穴的空间分离.     

可调能隙的光电器件结构——(AlAs)_ (n_l)/(GaAs)_(m_l)渐变周期超晶格

本文提出了一种具有渐变周期的(AlAs)_(nl)/(GaAs)_(ml)(1=1,2,…)超晶格,并采用递归方法计算了这种渐变周期超晶格的电子结构.其特点是带隙E_g在空间随(n_(?),m_(?))渐变.例如,对(AlAs)_4/(GaAs)_4(AlAs)_4、/(GaAs)_5/(AlAs)_4/(GaAs)_6/(AlAs)_4/(GaAs)_7结构,带隙由短周期一端的1.93eV变到长周期一端的1.78eV.同时导、价带边得到不同的调制,因而提高了电子与空穴电离率比值,有可能应用到作光电探测材料.     

Znse/GaAs超晶格的电子态和芯态激子

本文用半经验紧束缚法计算了ZnSe/GaAs(001)超晶格的能带结构,研究了其能隙与有效质量随层厚的变化.计算了(ZnSe)_5/(GaAs)_5超晶格中与杂质有关的芯态激子,其结果能说明相应异质结中束缚在Ga上的激子峰.本文还提出了该材料中导带底存在界面态.     

MOVPE生长GaAs／AlxGA1—xAs超晶格及其TEM表征

报道用金属有机汽相外延技术(MOVPE)生长GaAs/Al_xGa_(1-x)As超晶格结构材料及其光电器件应用,用横断面透射电子显微术(XTEM)表征外延层结构.在自电光效应光学双稳态器件(SEED)中,超晶格层-层之间界面清晰,厚度均匀,周期性完整.对某些用超晶格作缓冲层的高电子迁移率晶体管(HEMT)结构,观察到超晶格对生长面的平滑作用及间断生长造成的界面等.     

用静压光致发光研究GaAs/AlAs超短周期超晶格导带最低能级的特性

在77 K下,0—30 kbar 静压范围内研究了 GaAs/AlAs超短周期超晶格的静压光致发光.测得(GaAs)_1/(AlAs)_1的光致发光峰的压力系数为-1.35 meV/kbar。表明它的导带最低能级具有体材料X谷的特性而不是大多数理论计算所预计的L谷特性.测得(GaAs)_2/(AlAs)_1的光致发光峰的压力系数是8.69meV/kbar.表明它是 GaAs/AlAs超晶格中周期最短的Ⅰ类超晶格.     

GaAs/AlGaAs超晶格微带带宽的计算

利用MBE设备制备GaAs/AlGaAs超晶格材料,在低温(T=77K)下测量样品的光电流谱,从电子波动的观点出发,通过考虑电子波在超晶格阱层/势垒层的反射和干涉,讨论了超晶格的电子态.提出了一种计算超晶格微带带宽的方法,并计算了GaAs/AlGaAs超晶格的微带带宽.理论计算结果和实验结果符合得相当好.     

超晶格GaAs/(GaAl)As(100)和GaAs/Ge(100)的电子结构

本文采用经验紧束缚方法,计算了第一类半导体超晶格(GaAs)_(nl)/(Ga_xAl_(1-x)As)_(n2)(100)和(GaAs_n/(Ge)_n(100)的电子结构。对于GaAs/(GaAl)As,得到了能带边随层数(n_1,n_2)变化的关系及带边电子态的空间分布,并得出能隙随n和组分x的变化(n_1=n_2=n≤10),结果与现有实验值和其它理论计算基本相符;对于GaAs/Ge,计算了GaAs和Ge等厚时,间接能隙随层数的变化,考察了(GaAs)_5/(Ge)_5(100)的能带结构。在两种超晶格中,本文都报道了界面态的存在,讨论了超晶格的准二维性质。     

Growth and characteristics of p-type doped GaAs nanowire

The growth of p-type GaAs nanowires (NWs) on GaAs (111) B substrates by metal-organic chemical vapor deposition (MOCVD) has been systematically investigated as a function of diethyl zinc (DEZn) flow.The growth rate of GaAs NWs was slightly improved by Zn-doping and kink is observed under high DEZn flow.In addition,the I-V curves of GaAs NWs has been measured and the p-type dope concentration under the Ⅱ/Ⅲ ratio of 0.013 and 0.038 approximated to 1019-1020 cm-3.     

Si衬底上MBE长成的GaAs中剩余应力起源的研究(英文)

<正> High qualities of GaAs layers directly grown on Si substrates have been obtained by MBE. The residual stress in those MBE grown GaAs layers on     

CdTe/GaAs(111)B薄膜的MBE生长研究

采用分子束外延方法,在GaAs(111)B衬底上,生长CdTe薄膜,以求研制出用于液相外延生长碲镉汞(HgCdTe)薄膜的CdTe/GaAs(111)B复合衬底.通过理论分析和实验探索,优化了生长温度和Te/Cd束流比等重要生长参数,获得了质量较好的CdTe薄膜,再通过循环热处理,使CdTe/GaAs(111)B复合衬底的质量得到进一步的提高,X-射线回摆曲线半峰宽(FWHM)有明显的降低.为LPE-HgCdTe薄膜的生长打下了较好基础.     

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。     

Influence of growth temperatures on the quality of InGaAs/GaAs quantum well structure grown on Ge substrate by molecular beam epitaxy

Molecular beam epitaxy growth of an In_xGa_1-xAs/GaAs quantum well（QW） structure（x equals to 0.17 or 0.3） on offcut（100） Ge substrate has been investigated.The samples were characterized by atomic force microscopy,photoluminescence（PL）,and high resolution transmission electron microscopy.High temperature annealing of the Ge substrate is necessary to grow GaAs buffer layer without anti-phase domains.During the subsequent growth of the GaAs buffer layer and an In_xGa_1-xAs/GaAs QW structure,temperature plays a key role. The mechanism by which temperature influences the material quality is discussed.High quality In_xGa_1-x As/GaAs QW structure samples on Ge substrate with high PL intensity,narrow PL linewidth and flat surface morphology have been achieved by optimizing growth temperatures.Our results show promising device applications forⅢ-Ⅴcompound semiconductor materials grown on Ge substrates.     

Influence of the cap layer thickness on photoluminescence properties in strained InGaAs/GaAs single quantum wells

The influence of the GaAs cap layer thickness on the luminescence properties in strained In_0.20Ga_0.80As/GaAs single quantum well (SQW) structures has been investigated using temperature-dependent photoluminescence (PL) spectroscopy. The luminescence peak is shifted to lower energy as the GaAs cap layer thickness decreases, which demonstrates the effect of the GaAs cap layer thickness on the strain of InGaAs/GaAs single quantum wells (SQW). We find the PL quenching mechanism is the thermal activation of electron hole pairs from the wells into the GaAs cap layer for the samples with thicker GaAs cap layer, while in sample with thinner GaAs cap layer exciton trapping on misfit dislocations is dominated.     

Monolithic integration of an AlGaAs/GaAs DH LED with a GaAs FET driver

An AlGaAs/GaAs double heterostructure light emitting diode (LED) and a GaAs field effect transistor (FET) have been monolithically integrated on a GaAs substrate using a combination of liquid phase and molecular beam epitaxies. The electrical isolation between LED and FET has been achieved by inserting a molecular beam-grown high resistivity AlGaAs layer. A linear gate voltage-to-light power transfer characteristic with a 13 ns time constant has been demonstrated.     

Surface reconstructions and reflection high-energy electron diffraction intensity oscillations during homoepitaxial growth on nonmisoriented GaAs(111)B by MBE

The growth by molecular beam epitaxy of high quality GaAs epilayers on nonmisoriented GaAs(111)B substrates is reported. Growth control of the GaAs epilayers is achieved via in situ, real time measurement of the specular beam intensity of reflection high-energy electron diffraction (RHEED). Static surface phase maps of GaAs(111)B have been generated for a variety of incident As flux and substrate temperature conditions. The dependence of GaAs(111)B to be the optimum starting surface for the latter growth of mirror-smooth epilayers. Regimes of growth conditions are optimized in terms of the static surface phase diagram and the temporal RHEED intensity oscillations.     

Si/GaAs异质结界面态及其价带不连续性

本文报道用自洽EHT方法研究Si/GaAs异质结界面态分布和价带不连续性。用准共度晶格模型处理晶格失配问题,并对晶格常数作了修正。通过对Si/GaAs(111)、Si/GaAs(111)和Si/GaAs(110)异质结中Si应变和GaAs应变的情况,分别进行计算,得到界面态分布和价带不连续值等物理量,结果表明:它们不仅依赖于组成异质结的两种材料的体性质,而且还依赖于界面晶向和材料应变。文中给出了这些计算结果,并作了初步的讨论。