【作者】 邱永鑫；

【导师】 赵连城； 李美成； 刘国军；

【作者基本信息】 哈尔滨工业大学 ， 材料物理与化学， 2008， 博士

【摘要】 GaSb/GaAs薄膜及InAs/GaSb超晶格等GaSb基材料作为重要的光电功能材料在中远红外探测等领域展现出了极大的应用前景。本文主要研究了GaAs衬底上GaSb薄膜及InAs/GaSb超晶格材料的生长方法及其缺陷分布、结构特征和光电性质。本文系统研究了GaAs（001）衬底上GaSb薄膜的外延生长方法。采用二步生长法,引入低温缓冲层提高了GaSb外延层的质量。对GaSb低温缓冲层的生长速度、V/III比、厚度等进行了分析,得到了优化的低温GaSb缓冲层生长参数:生长速率为1.43μm/h,厚度为20nm,V/III束流比为3.0。通过引入低温GaSb缓冲层,降低了GaSb薄膜生长早期的温度,控制了生长初期岛的粗化过程,有效抑制了60°失配位错的形成,从而降低了GaSb薄膜中的穿透位错密度。开展了GaSb/GaAs薄膜的微观结构研究。透射电子显微镜观察发现, GaAs衬底上生长的GaSb薄膜中存在着大量的位错,包括位于{111}滑移面内的穿透位错和界面处的失配位错。利用高分辨X射线衍射对在沿[110]方向4°斜切的GaAs衬底上生长的GaSb薄膜中的位错分布进行了研究,结果表明（111）滑移面上的穿透位错密度高于（111）面上的穿透位错密度,[110]方向的位错间距大于[110]方向上的位错间距。这是由GaSb薄膜中的应力分布不均匀和GaSb岛生长的方向性决定的。另外,对斜切衬底引起的外延层中的错向角的大小和成因进行了分析,指出了在外延生长早期主要形成90°失配位错,而在随后的岛的合并过程中才形成60°位错,进而使错向角增大。未掺杂GaSb/GaAs薄膜的霍尔测试结果表明,GaSb/GaAs薄膜呈明显的p型导电特性,其77K下的空穴浓度为3.6×10¹⁵cm^-3,霍尔迁移率为4200cm²v^-1s^-1,这主要与GaSb中高浓度的Ga反位缺陷有关。实验研究发现,高温退火能够减少GaSb薄膜中的缺陷,降低载流子浓度,提高GaSb薄膜的迁移率。采用Sb浸渍的方法,利用Sb/As置换反应生长了高质量的GaAs/GaAsSb超晶格,并对衬底温度、Sb束流大小和Sb束流下暴露时间与超晶格中的Sb含量的关系进行了研究,实验结果表明,随着衬底温度的提高,Sb的解吸附程度增加,使超晶格中的Sb含量下降,在Sb4束流作用下,Sb/As置换反应很弱,仅局限在GaAs表面层中,因此对暴露时间和束流大小不敏感。利用分子束外延方法生长了InAs/GaSb超晶格,研究了生长中断和表面迁移增强（MEE）方法对超晶格材料的界面结构的影响。采用MEE工艺,可以在InAs/GaSb超晶格的界面处形成较好的GaAs型和InSb型界面;而采用生长中断的方法会使V族原子在界面处聚集,导致超晶格界面起伏较大,质量下降。InAs/GaSb超晶格的界面结构研究表明,界面结构对超晶格中的应变状态有很大的影响;与GaAs型界面相比,采用InSb型界面使超晶格的平均晶格常数增加。研究发现,在超晶格生长过程中可以通过调整界面生长工艺,控制界面结构来调节超晶格中的应变量。更多还原

【Abstract】 As a promising photoelectric materials, GaSb-based materials such as GaSb/GaAs and InAs/GaSb superlattices have made great progress in the fields of infrared detector in recent years. In this dissertation, growth method, dislocation distribution, structure and electrical properties of GaSb epilayer and InAs/GaSb superlattices grown on GaAs substrates by Molecular Beam Epitaxy （MBE） were investigated systematically.The growth of highly mismatched GaSb epilayer on GaAs （001） substrates was studied both experimentally and theoretically. The two-step growth method was used and low-temperature buffer layer was introduced in order to improve the quality of the GaSb epilayer. The growth parameters of low temperature （LT） GaSb buffer layer （including growth rate, thickness, and V/III beam equivalent pressure ratio ） were studied and it was found that the optimum growth rate, thickness, and V/III beam equivalent pressure ratio of the LT GaSb buffer were 1.43μm/h, 20nm and 3.0 respectively. The LT buffer restricted the formation of the 60°misfit dislocations（MDs） during the initial GaSb epilayer growth process and then reduced the density of the threading dislocations（TD） in the epilayer.The observation of TEM shows high density dislocations in the GaSb epilayer on GaAs substrates, including the TD in the {111} glide plane and the 90°MDs at the interface of the GaSb/GaAs. GaSb epilayers grown on GaAs （001） vicinal substrate 4°misoriented towards [110] direction were studied using high resolution X-ray diffraction （HRXRD）. We found that the densities of TDs in （111） plane were higher than in （111） plane and the TDs have a bigger spacing in the [110] direction than in [110] direction. This is a consequence of the unequal distribution of stress due to the miscut substrate and associated with the shape of GaSb island. The investigation of the tilt in the GaSb epilayer shows that the formation of 60°MDs is later than 90°MDs.The electrical properties of undoped GaSb/GaAs epilayer were studied by Hall measurements. The results show that the epilayers have Hall hole concentration p =3.6×10¹⁵cm^-3 and mobilityμ=4200cm²v^-1s^-1 at 77 K, which is related with the high concentration of Ga antisite defects （GaSb） in the GaSb epilayer. The experiment results show that the annealing treatment can effectively reduce the defects in the GaSb epilayer and then reduce the hole concentration, even improve the electronic mobility.High quality GaAs/GaAsSb superlattices were grown by the Sb soak using Sb/As displacement reaction on the GaAs layer surface. The effects of growth parameter of the substrate temperature, Sb flux and Sb soak time on the concentration of Sb were investigated. The results show that the Sb content in the superlattices decreased with the increasing of growth temperature due to the desorption of the Sb. The Sb4 flux and Sb4 soak time have no obvious effects on the structure of the superlattice, which means that the Sb/As exchange only happens in the surface monolayer of the GaAs.The InAs/GaSb superlattices were grown by MBE, and the influence of growth interruption and migration enhanced epitaxy （MEE） methods to the interface structure of superlattices were studied. High quality GaAs and InSb interface between InAs/GaSb superlattices were induced by the MEE technique and the Sb4-soak or As4-soak process resulted in the atom aggregation at the interface with the consequence of high interface roughness.Interface structure analysis of InAs/GaSb superlattices shows that the interface structure of InAs/GaSb superlattices has an effect on the strain in the superlattice. The InSb-type interface can increase the average lattice constant of the superlattice compared to the GaAs-type interface. Therefore, the strain can be accommodated by changing the growth parameters and controlling the interface structure.更多还原