GaAs/Ge的MOCVD生长研究

用常压MOCVD在Ge衬底上外延生长了GaAs单晶层,研究了GaAs和6e的极性与非极性材料异质外延生长,获得了质量优良的GaAs/Ge外延片,GaAs外延层X射线双晶衍射回摆曲线半高宽达16弧秒.10K下PL谱半峰宽为7meV.讨论了极性与非极性外延的界面反相畴问题和GaAs-Ge界面的Ga、Ge原子互扩散问题.     

两步生长法生长的Inx Ga1-x As/GaAs材料及性质

利用LP-MOCVD技术,采用两步生长法在GaAs(100)单晶衬底上外延生长InxGa1-xAs材料。通过扫描电子显微镜( SEM)与原子力显微镜( AFM)观察了缓冲层厚度对外延层表面形貌、表面粗糙度的影响;利用X射线衍射( XRD)分析了缓冲层厚度对外延层结晶质量的影响;利用拉曼光谱分析了缓冲层厚度对外延层材料合金有序度的影响;通过透射电子显微镜( TEM)观察了外延层材料位错的分布状态,计算了外延层的位错密度。实验结果表明,两步生长法生长的Inx Ga1-x As/GaAs异质结材料的缓冲层厚度存在一个最优值。     

MOCVD生长GaAs高质量掺碳研究

利用低压金属有机化合物汽相淀积(LP-MOCVD)系统,通过调节生长参量和掺杂工艺,得到了晶格质量高、表面形貌好且空穴浓度从8×10¹⁷到4×10²¹可控的掺碳GaAs外延层,最后给出一应用实例-用重掺碳的GaAs材料做级联GaInP/GaAs/Ge太阳能电池的隧道结.     

气相外延生长的ZnSe单晶薄膜及电致发光

用窄空间外延方法,在GaAs(100)衬底上外延生长了ZnSe(100)单晶薄膜.实验条件是,T衬=550℃,T源=650℃,H2-HCl气流速率为0.4-0.45l/min,生长速率为0.25-0.3μ/h.外延片在700℃的Zn和MnCl2蒸气中处理40-60分钟,以降低ZnSe的电阻率及掺入杂质Mn.利用这一外延层制作了MS结发光二极管,在反向偏压下获得黄色电致发光.     

磷化镓单晶外延工艺及其自支撑薄膜的制作

采用Ga—PCI_3—H_2系统开管式汽相外延的方法,在GaAs衬底上生长掺Zn的GaP单晶。经化学腐蚀去掉GaAs衬底得到自支撑GaP单晶薄膜。 研究了在P型GaAs衬底上外延P—型GaP的生长条件,生长速度与温度的关系,生长速度与输运气体中的PCI_3浓度的关系,以及晶向偏差,清洁条件等对外延层质薄的(井彡)响。     

LP-MOCVD两步生长法制备的InAs0.9Sb0.1/GaAs

利用LP-MOCVD技术,采用两步生长法,在(100)GaAs单晶衬底上生长高质量的InAs0.9Sb0.1。用扫描电镜、X射线单晶衍射、Hall测量以及Raman光谱等方法对材料进行了表征。分析了缓冲层和外延层生长温度对外延层表面形貌的影响。获得了表面光亮,室温载流子浓度为1.9×1017cm-3和迁移率为6214cm2/V.s的InAs0.9Sb0.1。在室温Raman光谱中观察到InAs0.9Sb0.1中InAs(LO)的233cm-1和InSb(LO)的187cm-1两种光学声子行为。     

InSb(111)衬底上外延生长二维拓扑绝缘体锡烯/铋烯的差异性研究

近些年,人们对拓扑材料体系的认知得到了飞速发展.随着量子信息科学与技术成为当下科学研究的热点,具有大能隙高稳定性的低维拓扑材料有从基础研究向应用探索的趋势发展.如何实现高质量、大面积的单晶生长是影响拓扑材料走向实用化的重要一步.本文报道了在具有Sb原子终止面的InSb(111)衬底上利用分子束外延技术生长低维拓扑绝缘体锡烯与铋烯的实验结果.实验中发现,无论是锡烯还是铋烯,起始外延阶段都会在衬底上形成单层的浸润层.由于锡原子之间的相互作用远强于其与衬底的表面结合力,因此浸润层呈岛状生长,晶畴岛与岛合并的过程中边界效应明显,导致薄膜实际上由大量小晶畴拼接而成,畴壁处的缺陷难以避免.而浸润层的晶体学质量又限制了后续锡烯薄膜的外延行为,因此实验发现难以实现高质量且层数准确可控的单晶锡烯薄膜生长.而铋原子与衬底表面的结合能强于原子之间的相互作用,能够在较高温度下实现浸润层的单层层状生长,高质量的浸润层为后续铋烯的生长提供了良好的外延过渡层,因此发现实验中更容易得到大面积的铋烯薄膜.本文实验结果及相关理解对于利用半导体衬底生长低维拓扑晶体薄膜具有指导意义.     

Co在GaAs(001)表面的分子束外延及其结构研究

报道了用高能电子衍射研究Co在GaAs(001)表面上分子束外延生长的实验结果.发现当生长温度为150℃时，Co膜的外延可以分为三个阶段：最初的3nm Co膜的晶体结构是体心立方亚稳相；接下来的4nm是复杂的多相结构；从7nm往后，Co膜则是单晶的六角密堆积结构热力学稳定相.这一新的实验结果，澄清了前人有关这一体系外延层晶体结构的矛盾之处，并清晰地建立了Co在GaAs(001)表面外延生长的物理图象. 关键词：     

OMVPE硒化锌薄膜的生长与激光特性

本文叙述了在GaAs衬底上用有机金属气相外延(OMVPE)法生长单晶ZnSe薄膜的方法。研究了生长温度,硒锌比对外延膜光电性能的影响。发现生长温度在285℃可以得到表面光亮、结晶性好、低阻、高迁移率、深中心浓度低的外延层。以光泵浦作激发研究了OMVPE ZnSe薄膜的受激发射性质并测量其光学增益。利用ZnSe/GaAs的自然解理面形成的光反馈腔制成了激光器。该激光器的工作温度可以延续到150K。     

在MOCVD外延生长中V/Ⅲ比对Al_xGa_(1-x)As外延层中A1组分分布的影响

本实验首次观察到用MOCVD方法在GaAs基片上外延生长Al_xGa_(1-x)As/GaAs薄膜结构时,生长中所用的Ⅴ/Ⅲ比对外延层中Al组份x的分布的影响.当Ⅴ/Ⅲ比较低时,外延层中的Al组份出现很明显的层状阶梯形三层分布:靠近基片的一层中x值较低,而在外延层的表面层中x值较高.随着生长中所用的Ⅴ/Ⅲ比增加时,Al组份的分布趋于均匀.利用GaAs的高温热分解和Ga、As离子在晶体中的热扩散及其对外延生长的影响,对这一现象作了初步解释.     

Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. I. Molecular beam epitaxy

GaAs/Ge/GaAs heterostructures in which the GaAs layer lattice on Ge is rotated at a right angle to the substrate plane are grown by molecular-beam epitaxy (MBE). Such heterostructures are grown in different epitaxial setups for GaAs and for Ge with wafer transfer through air tor the first time. It is proposed to use surfactants (Bi, Sb) to control GaAs layer nucleation on Ge.     

Molecular beam epitaxy growth of GaAs on an offcut Ge substrate

Molecular beam epitaxy growth of GaAs on an offcut Ge (100) substrate has been systemically investigated. A high quality GaAs/Ge interface and GaAs film on Ge have been achieved. High temperature annealing before GaAs deposition is found to be indispensable to avoid anti-phase domains. The quality of the GaAs film is found to strongly depend on the GaAs/Ge interface and the beginning of GaAs deposition. The reason why both high temperature annealing and GaAs growth temperature can affect epitaxial GaAs film quality is discussed. High quality In_0.17Ga_0.83As/GaAs strained quantum wells have also been achieved on a Ge substrate. Samples show flat surface morphology and narrow photoluminescence line width compared with the same structure sample grown on a GaAs substrate. These results indicate a large application potential for III--V compound semiconductor optoelectronic devices on Ge substrates.     

Stranski–Krastanow growth of multilayer In(Ga)As/GaAs QDs on Germanium substrate

We have described Stranski–Krastanow growth of multilayer In(Ga)As/GaAs QDs on Ge substrate by MBE. The growth technique includes deposition of a thin germanium buffer layer followed by migration-enhanced epitaxy (MEE) grown GaAs layer at 350°C. The MEE layer was overgrown by a thin low-temperature (475°C) grown GaAs layer with a subsequent deposition of a thick GaAs layer grown at 590°C. The sample was characterized by AFM, cross-sectional TEM and temperature-dependent PL measurements. The AFM shows dense formation of QDs with no undulation in the wetting layer. The XTEM image confirms that the sample is free from structural defects. The 8 K PL emission exhibits a 1051 nm peak, which is similar to the control sample consisting of In(Ga)As/GaAs QDs grown on GaAs substrate, but the observed emission intensity is lower. The similar slopes of Arrhenius plot of the integrated PL intensity for the as-grown QD sample grown on Ge substrate as well as for a reference QD sample grown on GaAs substrate are found to be identical, indicating a similar carrier emission process for both the samples. This in turn indicates coherent formation of QDs on Ge substrate. We presume due to the accumulated strain associated with the self-assembled growth of nanostructures on Ge that nonradiative recombination centers are introduced in the GaAs barrier in between the QD layers, which in turn degrades the overall optical quality of the sample.     

Orientation-patterned templates GaAs/Ge/GaAs for nonlinear optical devices. II. Investigation of properties

GaAs/Ge/GaAs heterostructures in which GaAs layer lattices are rotated at a right angle in the substrate plane are studied. High quality of heterostructures is confirmed by X-ray diffraction and photoluminescence methods.     

AFM morphological characterization and Raman study of germanium grown on (111)GaAs

In this communication we report on the growth of Ge heterolayers on (100), (111)Ga and (111)As surfaces of GaAs substrates. Arsenic can play a role as both dopant and surfactant, changing the growth mechanism for the Ge/GaAs growth on (001) oriented substrates. The use of substrates oriented in different directions can change the growth mode and produce different results, since surface polarity can induce different growth modes: we have compared the results on (111) substrates with respect to the non-polar surface case.The growth behavior on (001), (111)Ga and (111)As substrates is discussed. The layer morphology was investigated by Atomic Force Microscopy and Raman spectroscopy has been carried out as a function of the sample thickness.     

Chemical characterization by XPS of Cu/Ge ohmic contacts to n-GaAs

Chemical composition of Cu/Ge layers deposited on a 1 μm thick n-type GaAs epitaxial layer (doped with Te to a concentration of 5 × 10¹⁸ cm⁻³) and its interface were examined ex situ by XPS combined with Ar⁺ sputtering. These measurements indicate a diffusion of Cu and Ge from the Cu/Ge layer towards GaAs and, also, an out-diffusion of Ga and As from the GaAs layer to the metallic films. The Auger parameter corrected Auger spectra and XPS spectra show only Cu and Ge metals in the in the Cu/Ge layer and in the interface.     

Observation of interface plasmon excitation in photoemission spectroscopy from the heterostructures Cu/RbF/GaAs(100) and Cu/RbF/Ge(100)

Synchrotron radiation photoelectron spectra taken at 100 eV photon energy have been measured to characterize the interface reactions of the metal-insulator-semiconductor systems Cu/RbF/GaAs(100) and Cu/RbF/Ge(100). In comparision, similar sequences are studied on the Cu/GaAs(100) and Cu/Ge(100) interfaces without the RbF interlayer. After Cu-deposition of 1–4 Å on RbF-covered (10–14 Å) GaAs and Ge surfaces, shoulder peaks appear on both the Ga 3d and Ge 3d core levels. The shoulder peaks are shifted 1.1 and 1.4 eV to higher binding energy for the Ga 3d and Ge 3d levels, respectively. The Rb 4p and F 2p peak positions are slightly shifted between 0.25 and 0.5 eV. The broad second Ga 3d and Ge 3d peaks can be correlated to plasmon loss of electrons from these levels in a two-dimensional Rb metal-like layer formed at the Cu/RbF interface. The excitation energy of a Rb surface plasmon in a Cu-Rb-RbF system is calculated to be 1.3 eV.     

Formation of ohmic contacts to n-GaAs by ion beam mixing and annealing

The present study has shown that by using ion beam mixing on the Au-Ge/Ni/GaAs system, followed by an annealing step, an ohmic contact to n-GaAs can be formed. The morphology of the contacts fabricated in this way were better than the contacts without the ion implantation step. From Auger depth profiles, it follows that a region of uniformly mixed nickel/germanium/arsenic system formed, which is spreaded out uniformly throughout the metallization layer. In contrast, the contacts which were only annealed exhibited regions of non-uniformly mixed Ni and Ge and of Ni and As. The Auger study also reveals that more Ni has diffused into the GaAs for the ion implanted contacts and therefore helps to trap more Ge in the substrate, which is beneficial for doping purposes.     

有源层掺杂剂对Ga1-xAlxAs/GaAs双异质结发光管特性的影响

本文研究了由液相外延技术生长的GaAIAs/GaAs双异质结材料制成的发光管,有源层掺杂剂对器件特性的影响结果表明,器件结构和器件制作工艺相同的GaAIAs/GaAs发光管,有源层掺Si可获得较大的光输出功率,而频响特性<15MHz,波长在8700Å以上;对有源层掺Ge器件,光输出功率低于掺Si器件,而频响特性则>15MHz,波长可控制在8200Å~8500Å.深能级测量表明二者有不同的深能级位置,对掺Si(氧沾污)器件,Ec-ET≈0.29eV,而掺Ge器件ET-Ev≈0.42eV.两种掺杂剂对有源层暗缺陷的影响尚无明显区别.