【作者】 熊敏；

【导师】 赵连城； 李美成；

【作者基本信息】 哈尔滨工业大学 ， 信息功能材料与器件， 2010， 博士

【摘要】 以GaSb与AlSb为代表的6.1 （A|°）锑化物半导体材料及其构成的超晶格等低维结构在中长波红外探测领域有着重要的应用前景,锑化物外延生长中的表面扩散以及V族元素置换等材料问题在很大程度上制约着薄膜与低维结构的表面与界面质量。本文生长了GaSb薄膜、GaAs/GaAsSb超晶格与InAs/GaSb超晶格,研究了锑化物表面再构对外延生长中薄膜形貌、缺陷形成、Sb/As置换以及表面偏析等的影响,设计并制备了基于InAs/GaSb超晶格的势垒型红外探测器并分析了其光电性能。论文的主要研究内容包括:采用分子束外延制备了同质与异质GaSb薄膜,原子力显微镜图像表明薄膜表面均呈现丘形形貌,并且沿[ 110]方向拉长。通过高分辨X射线衍射（HRXRD）研究了在GaAs衬底上生长的GaSb异质薄膜<110>方向的位错密度、共格长度、晶面倾角与应变弛豫度。实验结果表明,采用AlSb缓冲层后,在[ 110]方向的位错密度下降,应变弛豫呈现各向同性。结合实验现象,通过第一性原理计算研究了Ga原子在GaSb（001）-（4×3）再构表面的吸附与扩散特性。研究发现,再构表面二聚体的类型以及排列方式决定着表面吸附点、鞍点的位置与吸附能。Ga原子在GaSb（001）-（4×3）表面扩散具有明显的各向异性, [ 110]方向是表面的快速扩散方向。另外,再构表面晶胞平移基矢的研究表明,AlSb（001）-c（4×4）具有的较高对称性使其相对（4×3）再构不容易发生表面晶胞错动,尤其沿[ 110]方向能有效的抑制异质外延中90°位错网相对错动而形成60°位错。通过HRXRD与高分辨透射电子显微镜（HRTEM）分析了Sb浸渍形成的GaAs/GaAsSb超晶格中的GaSb含量,观察到了超晶格界面处Sb富集所引入局域态的光致发光。运用热力学估计了Sb在超晶格表面发生吸附的条件。引入表面再构模型研究了GaSb覆盖GaAs（GaSb/GaAs）表面的Sb-for-As置换,发现在应变的GaSb/GaAs表面上Sb原子置换具有弱Ga-As键的As原子在能量上是占优的。表面的Sb-for-As置换能稳定GaAsSb层生长中Sb浸渍形成的GaSb,使其难以被后续GaAs生长引起的As-for-Sb所破坏。采用sp3s*模型与最近邻近似的经验紧束缚方法计算了GaSb、AlSb与InAs/GaSb超晶格能带结构,分析了超晶格层厚、界面类型以及表面再构引起的Sb偏析对超晶格能带结构的影响。拟合了77K下AlSb的紧束缚参数并用于含有AlSb层的InAs/GaSb超晶格（M型超晶格）的电子与空穴子带带边、有效带隙与有效质量的计算。分析了势垒层为AlGaSb的M型超晶格中Al组分变化对超晶格应变与能带结构的影响。采用分子束外延制备了InAs/GaSb超晶格,通过HRXRD、Raman散射与HRTEM分析了超晶格的应变与界面结构。设计并制备了有源区为InAs₈/GaSb₈,势垒区为InAs₁₁/GaSb₂/AlSb₆/GaSb₂超晶格的势垒型红外探测器。器件测试结果表明, 90K下探测器50%截止波长为4.9μm ,零偏条件下黑体探测率为2.8×10⁹cm·Hz^1/2/W,-0.5V偏压时器件的暗电流密度为50mA/cm²。更多还原

【Abstract】 The Sb-based III-V semiconductor compounds and their heterostructures such as superlattices （SL） and quantum wells have attracted much attention for their applications in infrared detection recently. The material isssues such as poor surface diffusion and As/Sb exchange limit improvements of the antimonide heterostructures. The main topic in this dissertation is the study of antimonide surface reconstructions and the effects on the surface morphology, 60°dislocation formation, and Sb-for-As exchange in epitaxy. The other topic in this thesis is the design and fabrication of barrier infrared detector based on InAs/GaSb SL. The main research and achievments are as follows:Homoepitaxial and heteroepitaxial GaSb films were grown by molecular beam epitaxy （MBE）. Atomic force microscopy （AFM） shows that all the GaSb films present mound morphology with elongation along [ 110] direction. The dislocation density, tilt and coherent length resulting from dislocation, and relaxation degree along <110> directions were characterized by high-resolution X-ray diffraction （HRXRD）. The mesurements demonstrate that the AlSb buffer layer can increase relaxation degree of GaSb heteroepitaxial film along [ 110] direction with deduction of density of threading dislocation.The adsorption and diffusion properties of a Ga adatom deposited on GaSb（001）-α/β（4×3） were investigated by first-principles calculations. Combining with the experimental data, the calculation results have been utilized to interpret the morphology anisotropy of GaSb films: the distribution and depth of adsorption sites and saddle points are determined by the type and arrangement of the surface dimer row, and [ 110] is fast diffusion direction of Ga adatoms on the GaSb（001）-（4×3） surface. Besides, the study of bravais lattice diversity reveal that, the 60°misfit dislocations nucleation through shift of 90°dislocation array on the AlSb（001）-c（4×4） surface could be suppressed owing to the high symmetry of the reconstruction.HRXRD and high-resolution transmission electron microscopy （HRTEM） were performed to estimate the GaSb component of GaAs/GaAsSb SL which grown by Sb soak method. Luminescence from GaAsSb well and Sb-rich regions were observed and the Sb surface incorporation in the SL growth were analyzed thermodynamically. Furthermore, Sb-for-As exchange at the GaSb covered GaAs （GaSb/GaAs） surface was investigated using first principle calculations. Sb substitution for subsurface As atoms with weak Ga–As bonding arrangements are energetically favored at the strained GaSb/GaAs surface. After the Sb-for-As exchange, the formed GaSb layer can be stabilized against degradation from As-for-Sb exchange in the growth of GaAs/GaAsSb SL.Band structure of GaSb, AlSb and InAs/GaSb SL were calculated by empirical tight-binding method （ETBM） within the frame of sp3s* base sets and first-nearest-neighbor approximation. The effects of thickness, interface structure and surface segregation on band structure were analyzed. The band structure of InAs/GaSb SL modified by Al（Ga）Sb layers （M-SL） was investigated by tight-binding parameters of AlSb at 77K, which fitted to the reported band data.We grown the InAs/GaSb SLs with different interface type by MBE, interface structure of SLs was characterized by Raman scattering and cross-sectional HRTEM. The barrier infrared detector consisting of InAs/GaSb SL was design and fabricated. At 90K, a 5μm 50% cutoff detector exhibits a dark current 50mA/cm² with -0.5V bias, and a blackbody detectivity of 2.8×10⁹cm·Hz^1/2/W with zero bias.更多还原