低能离子束沉积制备GaAs:Gd的研究

对室温条件下用低能离子束沉积得到的GaAs∶Gd样品,借助X射线衍射(XRD)和高分辨X射线衍射(HR-XRD)进行了结构分析,结果表明没有出现新的衍射峰,并且摇摆曲线的形状与Gd的注入计量密切相关.运用X光电子能谱仪对比分析了Gd注入后,衬底中主要元素Ga2p和As3d的化学位移,以及不同计量的样品中注入的Gd4d芯能级束缚能的变化,并分析了铁磁性产生的可能原因.     

低能离子束沉积制备GaAs:Gd的研究

对室温条件下用低能离子束沉积得到的GaAs∶Gd样品,借助X射线衍射(XRD)和高分辨X射线衍射(HR-XRD)进行了结构分析,结果表明没有出现新的衍射峰,并且摇摆曲线的形状与Gd的注入计量密切相关.运用X光电子能谱仪对比分析了Gd注入后,衬底中主要元素Ga2p和As3d的化学位移,以及不同计量的样品中注入的Gd4d芯能级束缚能的变化,并分析了铁磁性产生的可能原因.     

大剂量Mn离子注入GaAs的性质

在室温条件下在半绝缘性GaAs衬底上进行了大剂量Mn离子的低能注入,并进行了不同条件的退火.借助于X射线衍射(XRD)和高分辨X射线衍射(HR-XRD)进行了结构分析,经过退火后生成的新相衍射峰增多,根据衬底(004)峰摇摆曲线分析结果退火后更多的Mn离子进入晶格.运用原子力显微镜分析了样品的表面,发现退火后突起的起伏度增加.磁性分析表明,退火样品的磁化强度增大.     

大剂量Mn离子注入GaAs的性质

在室温条件下在半绝缘性GaAs衬底上进行了大剂量Mn离子的低能注入,并进行了不同条件的退火.借助于X射线衍射(XRD)和高分辨X射线衍射(HR-XRD)进行了结构分析,经过退火后生成的新相衍射峰增多,根据衬底(004)峰摇摆曲线分析结果退火后更多的Mn离子进入晶格.运用原子力显微镜分析了样品的表面,发现退火后突起的起伏度增加.磁性分析表明,退火样品的磁化强度增大.     

大剂量Mn离子注入GaAs的性质

在室温条件下在半绝缘性GaAs衬底上进行了大剂量Mn离子的低能注入，并进行了不同条件的退火. 借助于X射线衍射(XRD)和高分辨X射线衍射(HR-XRD)进行了结构分析，经过退火后生成的新相衍射峰增多，根据衬底(004)峰摇摆曲线分析结果退火后更多的Mn离子进入晶格. 运用原子力显微镜分析了样品的表面，发现退火后突起的起伏度增加. 磁性分析表明，退火样品的磁化强度增大.     

(Ga,Mn,As)/GaAs的发光谱

利用低能双离子束外延技术 ,在 4 0 0℃条件下生长样品 (Ga,Mn,As) / Ga As.样品光致发光谱出现三个峰 ,即1.5 0 4 2 e V处的 Ga As激子峰、1.4 875 e V处的弱碳峰和低能侧的一宽发光带 .宽发光带的中心位置在 1.35 e V附近 ,半宽约 0 .1e V.在 84 0℃条件下对样品进行退火处理 ,退火后的谱结构类似退火前 ,但激子峰和碳杂质峰的峰位分别移至 1.5 0 6 5 e V和 1.4 894 e V,同时低能侧的宽发光带的强度大大增加 .这一宽发射带的来源还不清楚 ,原因可能是体内杂质和缺陷形成杂质带 ,生成 Mn2 As新相 ,Mn占 Ga位或形成 Ga Mn As合金     

生长温度对In0.82Ga0.18As表面形貌和结晶质量的影响

采用低压金属有机化学气相沉积(LP-MOCVD)技术,在InP衬底上外延生长In0.82Ga0.18As.研究生长温度对In0.82Ga0.18As表面形貌、结晶质量和Ⅲ族源铟镓比的影响.扫描电子显微镜观察样品的表面形貌.X射线衍射用于表征材料的组分和结晶质量.结果表明,生长温度强烈地影响In0.82Ga0.18As材料的表面形貌和结晶质量.样品的表面形貌随生长温度的增加由典型的2D生长模式过渡到3D生长模式.X射线衍射曲线半峰全宽为1224、1454、2221、2527 S,分别对应于生长温度为410、430、450、470℃四个样品.此外,Ⅲ族源铟镓比值也随生长温度的增加从0.42增大到4.62.     

用分子束外延技术在GaAs(110)衬底上生长AlGaAs材料

采用分子束外延技术在GaAs(110)衬底上制备了一系列生长温度和As2/Ga束流等效压强比不同的样品,通过室温光致发光谱、高分辨X射线衍射仪和低温光致发光谱对这些样品进行了分析,找到了在GaAs(110)衬底上生长高质量高Al组分的Al0.4Ga0.6As生长条件.     

用分子束外延技术在GaAs(110)衬底上生长AlGaAs材料

采用分子束外延技术在GaAs(110)衬底上制备了一系列生长温度和As2/Ga束流等效压强比不同的样品,通过室温光致发光谱、高分辨X射线衍射仪和低温光致发光谱对这些样品进行了分析,找到了在GaAs(110)衬底上生长高质量高Al组分的Al0.4Ga0.6As生长条件.     

MBE生长RTD材料的X射线双晶衍射研究

用分子束外延技术(MBE)生长了GaAs基共振隧穿二极管(RTD)的材料结构,利用X射线双晶衍射(XRD)方法对材料进行了测试分析.结果表明,材料的双晶衍射峰半峰宽达到16.17",GaAs层与In0.1Ga0.9As层的相对晶格失配率仅为0.015 6%.对实验样品进行了双晶衍射回摆曲线的模拟,模拟结果与测试结果符合较好,说明生长的RTD材料结构与设计相符合.通过制成器件对材料进行验证,室温下对器件进行直流测试,PVCR达到5.1,峰值电流密度达到73.6 kA/cm2.     

A study of the process of decomposition of supersaturated GaAs:Fe solid solution by scanning probe microscopy

Using an atomic-force microscope, the decomposition of the supersaturated solid solution of iron-doped GaAs (GaAs:Fe) is studied. GaAs:Fe samples were obtained in the course of high-temperature diffusion of Fe into GaAs and subsequent annealing at a temperature by 200°C below the doping temperature. The measurements are performed for transverse cleavages along the cleavage planes of the GaAs:Fe wafers. It is shown that, during annealing of the GaAs:Fe samples, the supersaturated alloy decomposes with the formation of particles of the second phase from ∼50 nm to ∼1 μm in size. The particles of the second phase possess ferromagnetic properties at room temperature.     

Ferromagnetic Properties of Five-Period InGaMnAs/GaAs Quantum Well Structure

The effect of Mn was investigated in a synthesized multilayer system made up of five layers of InMnGaAs/GaAs quantum well (QW) grown on semi-insulating (100)-oriented substrates prepared by low-temperature molecular beam epitaxy. Magnetic moment measurements on a superconducting quantum interference device magnetometer revealed the presence of ferromagnetism with a Curie temperature above room temperature in a five-layer InGaMnAs/GaAs QW structure in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements powerfully confirmed the second phase founding of ferromagnetic GaMn and MnAs clusters. The ferromagnetism existing in five layers of InMnGaAs/GaAs QW is not intrinsic, but extrinsic due to the presence of Mn dopant clusters such as GaMn and MnAs clusters.     

A study of chemical beam epitaxy of GaAs using tris-dimethylaminoarsenic

The growth of GaAs by chemical beam epitaxy using triethylgallium and trisdimethylaminoarsenic has been studied. Reflection high-energy electron diffraction (RHEED) measurements were used to investigate the growth behavior of GaAs over a wide temperature range of 300–550°C. Both group III- and group Vinduced RHEED intensity oscillations were observed, and actual V/III incorporation ratios on the substrate surface were established. Thick GaAs epitaxial layers (2–3 μm) were grown at different substrate temperatures and V/III ratios, and were characterized by the standard van der Pauw-Hall effect measurement and secondary ion mass spectroscopy analysis. The samples grown at substrate temperatures above 490°C showed n-type conduction, while those grown at substrate temperatures below 480°C showed p-type conduction. At a substrate temperature between 490 and 510°C and a V/III ratio of about 1.6, the unintentional doping concentration is n ∼2 × 10¹⁵ cm⁻³ with an electron mobility of 5700 cm²/V·s at 300K and 40000 cm²/V·s at 77K.     

GaAs衬底上Mn／Sb多层铁磁膜的磁光克尔效应

利用超高真空电子束蒸发技术GaAs(100）上生长Mn/Sb多层膜,并经短时间热退火处理分别研究了其退火前后的磁性、磁光克尔效应及相应规律,退火前Mn/Sb膜在室温下即具有较强的铁磁特性,其易磁化轴在膜面内,样品表面由密集的岛状铁磁颗粒组成,未能观测到纵向（H//平面）克尔效应,经350℃、20min退火的样品显示了最大饱和磁化强度Ms和最小矫顽力Hc,X射线衍射测量表明膜为MnSb单晶并具有均匀的铁磁特性,能观测到显著的要有向和纵向磁光克尔效应,其随磁场变化表现出相应于磁化强度的磁带行为。     

Realization of n-channel and p-channel high-mobility (Al,GA)As/GaAs heterostructure insulating gate FET's on a planar wafer surface

Self-aligned gate by ion implantation n-channel and p-channel high-mobility (Al,Ga)As/GaAs heterostructure insulated-gate field-effect transistors (HIGFET's) have been fabricated on the same planar wafer surface for the first time. Enhancement-mode n-channel (Al,Ga)As/GaAs HIGFET's have demonstrated extrinsic transconductances of 218 mS/mm at room temperature and 385 mS/mm at 77 K. Enhancement-mode p-channel (Al,Ga)As/GaAs HIGFET's have demonstrated extrinsic transconductances of 28 mS/mm at room temperature and 59 mS/mm at 77 K. There are the highest transconductance values ever reported on a p-channel FET device.     

Hot plasma chemical vapor deposition of GaN on GaAs(100) substrate

GaN films have been deposited on GaAs(lOO) substrates by a novel growth technique, hot plasma chemical vapor deposition. A radio frequency N plasma source with high power, up to 5 kW, provides an abundance of nitrogen atoms during growth. In addition, strong ultraviolet emissions from the hot plasma irradiate onto the substrate and promote the dissociation of triethylgallium, this results in growth of GaN at very low temperature (even at room temperature). In this paper, we describe the characteristics of hot nitrogen plasma and present the results of the low temperature growth of GaN. In addition, we have investigated the effects of the nitridation of GaAs substrates. Reflection high energy electron diffraction indicates the formation of a surface cubic nitrided layer on the pretreated GaAs. The GaN films grown on fully nitrided GaAs(l00) substrates are of dominantly cubic structures.     

ZnTe/Si(211)与ZnTe/GaAs(211)异质结构的热应变研究

通过理论计算获得ZnTe/Si（211）与ZnTe/GaAs（211）异质结构样品室温下的热应变分布与曲率半径,并采用激光干涉仪测量两个样品室温下的曲率半径。研究发现,在（211）面上进行异质外延,两个互相垂直的晶向方向[1-1-1]和[01-1]的应变分布呈现各向异性,且沿两个方向上的表面曲率半径亦存在差异。ZnTe/GaAs（211）样品的激光干涉测量结果与理论计算较为吻合,均为同一数量级的表面曲率半径方向为负的张应变,ZnTe/Si（211）样品的测量结果则存在较大差异。由于Si衬底在高温脱氧的过程中产生了表面曲率半径方向为正的塑性形变,在一定程度上降低了外延ZnTe后异质结构的弯曲程度,减小了热失配应变。     

Room Temperature Ferromagnetismin Co-doped ZnO Bulks

Pure single phase of Zn0.95Co0.05O bulks were successfully prepared by solidstate reaction method.The effects of annealing atmosphere and temperature on the room temperature ferromagnetic behavior were investigated. The results show that the airannealed samples has similar weak ferromagnetic behavior with the assintered samples, but the obvious ferromagnetic behavior is observed for the samples annealed in vacuum or Ar/H2 gas, indicating that the strong ferromagnetism is associated with high oxygen vacancies density. High saturation magnetization Ms=0.73 μB/Co and eoercivity Hc=233.8Oe are obtained for the Ar/H2 annealed samples with pure single phase structure when annealing temperature is 600 ℃.     

3D defect distribution induced by focused ion beam irradiation at variable temperatures in a GaAs/GaAlAs multi quantum well structure

In this study, we propose a new characterisation method of the damage distribution using a GaAs/GaAlAs multi quantum well structure (MQW). Three quantum wells are used as high sensibility sensors, in relation to the damage created during the FIB irradiation through photoluminescence (P.L.) intensity measurements.

We have compared the effect of a Ga⁺ focused ion beam irradiation on the MQW structure, which was kept either at room temperature, or near the liquid nitrogen temperature (80 K) during the bombardment. The surface ion dose was kept constant at 10¹⁵ ions/cm². No subsequent annealing was performed. Irradiated samples were characterised using low temperature (1.7 K) and spatially resolved photoluminescence experiments.     

Sulfur passivation of semi-insulating GaAs: Transition from Coulomb blockade to weak localization regime

The sulfur passivation of the semi-insulating GaAs bulk (SI GaAs) grown in an excess phase of arsenic is used to observe the transition from the Coulomb blockade to the weak localization regime at room temperature. The I–V characteristics of the SI GaAs device reveal nonlinear behavior that appears to be evidence of the Coulomb blockade process as well as the Coulomb oscillations. The sulfur passivation of the SI GaAs device surface results in enormous transformation of the I–V characteristics that demonstrate the strong increase of the resistance and Coulomb blockade regime is replaced by the electron tunneling processes. The results obtained are analyzed within frameworks of disordering SI GaAs surface that is caused by inhomogeneous distribution of the donor and acceptor anti-site defects which affects the conditions of quantum- mechanical tunneling. Weak localization processes caused by the preservation of the Fermi level pinning are demonstrated by measuring the negative magnetoresistance in weak magnetic fields at room temperature. Finally, the studies of the magnetoresistance at higher magnetic fields reveal the h/2e Aharonov–Altshuler–Spivak oscillations with the complicated behavior due to possible statistical mismatch of the interference paths in the presence of different microdefects.