Ge／Pd／n—GaAs低阻欧姆接触的SIMS分析

采用Ｇｅ／Ｐｄ／ＧａＡｓ结构和快速热退火在ｎ－ＧａＡｓ上形成了低阻欧姆接触，利用二次离子质谱技术揭示和讨论了低欧姆接触形成的机理。比较了采用Ｘ＾＋和ＧｓＸ＾＋信号检测的Ｇｅ，Ｐｄ，Ｇａ和Ａｓ的深度分布。结果表明采用ＣｓＸ＾＋可以提供更准确的结果和成分信息。     

利用快速热退火在n-GaAs上形成浅欧姆接触

采用超高真空电子束蒸发设备和快速热退火工艺制备GaAs／Pd／AuGe／Ag／An多层结构和测量比接触电阻车所需的传输线模型。研究了比接触电阻率与退火温度和时间关系，400～500℃之间退火的欧姆接触的比接触电阻车约为10（－6）Ωem2。接触层表面光滑、界面平整。利用俄歇电子谱（AES）、二次离子质谱（SIMS）、X射线衍射（XRD）和扫描电镜（SEM）研究了欧姆接触的微观结构和形成机理。     

p-GaN表面制备低阻欧姆接触电极的几个关键问题

优良的光电特性使得GaN材料成为当今半导体器件研究领域的热点,但高功函数和低载流子浓度使p-GaN表面难以制备低阻欧姆接触电极、严重妨害了GaN基器件的热稳定性和输出功率.如何制备具有低阻欧姆接触特性的p-GaN电极已成为一个关键的科学和技术问题.探讨了影响p-GaN欧姆接触特性的几个关键因素,如表面预处理工艺、电极材料的选择和厚度、退火工艺等,对此方面的最新进展进行评述和归纳,并提出自己的创新性研究思路.     

Si基n型GaN的欧姆接触研究

GaN材料在光电子器件领域的广泛应用前景使得金属与其欧姆接触的研究成为必然。本文对Si基n型GaN上的Al单层及Ti/Al双层电极进行了研究。通过对不同退火条件下的I U特性曲线 ,X射线衍射以及二次离子质谱分析 ,揭示了界面固相反应对欧姆接触的影响 ,提出了改善这两种电极欧姆接触的二次退火方法     

Si基n型GaN的欧姆接触研究

GaN材料在光电子器件领域的广泛应用前景使得金属与其欧姆接触的研究成为必然。本对Si基n型GaN上的A1单层及Ti/Al双层电极进行了研究。通过对不同退火条件下的I—U特性曲线，X射线衍射以及二次离子质谱分析，揭示了界面固相反应对欧姆接触的影响，提出了改善这两种电极欧姆接触的二次退火方法。     

Au/Ti/W/Ti与n-GaAs欧姆接触的特性研究

用磁控溅射系统和快速合金化法制备了Au/Ti/W/Ti多层金属和n-GaAs材料的欧姆接触,用传输线法对其比接触电阻进行了测试,并利用俄歇电子能谱(AES)和X射线衍射图谱(XRD)对接触的微观结构进行了研究。结果表明该接触在700℃时比接触电阻为1.5×10~(-4)Ω·cm~2,快速合金化后呈现欧姆特性可能与接触界面处生成的TiAs相有关。     

Si基GaN上的欧姆接触

研究了Ｓｉ基ＧａＮ上的欧姆接触,对在不同的合金化条件下铝（Ａｌ）和钛铝铂金（Ｔｉ／Ａｌ／Ｐｔ／Ａｕ）接触在不同的合金下的性质作了详尽的分析。Ａｌ／ＧａＮ在４５０℃氮气气氛退火３ｍｉｎ取得最好的欧姆接触率７．５＊１０＾－３Ω．ｃｍ＾２,而Ｔｉ／Ａｌ／Ｐｔ／Ａｕ／ＧａＮ接触在６５０℃氮气气氛退火２０ｓ取得最好的欧姆接触８．４＊１０＾－５Ω．ｃｍ＾２,而且Ｔｉ／Ａｌ／Ｐｔ／Ａｕ／ＧａＮ接触有较好的热稳定     

Zn+注入对p-GaN/Ni/Au欧姆接触特性的影响

首次采用离子注入工艺研究金属电极和p-GaN的欧姆接触特性.Zn为Ⅱ族元素,可以提高p-GaN表面的栽流子浓度,对p-GaN/Ni/Au(5/10nm)界面处进行Zn+注入.经Zn+注入后的样品在空气氛围中快速热退火处理5min,以减少离子注入带来的晶格损伤.研究发现Zn+注入改善了p-GaN/Ni/Au的欧姆接触特性,接触电阻率ρc从10-1Ω·cm2数量级降低到10-3Ω·cm2数量级.研究了不同Zn+注入剂量(5×1015、1×1016、5×1016cm-2)对接触电阻率的影响,在注入剂量为1×1016cm-2、300℃下退火得到最优的接触电阻率为1.45×10-3Ω·cm2.用扫描电子显微镜观察了离子注入前后的表面形貌变化,探讨了接触电阻率改变的内在机制.     

p-GaN表面Ni/Au电极欧姆接触特性的Pt+注入改性研究

对p-GaN/Ni/Au(5/10nm)界面处进行Pt+注入,注入后的样品在空气中快速热退火处理5min,发现金属电极和p-GaN的欧姆接触特性得到明显的改善,接触电阻率从101-Ω·cm2数量级降低到10-3Ω·cm2数量级.通过研究在不同Pt+注入剂量(5×1015、1×1016、2×1014cm-2)和退火温度下接触电阻率的变化规律.在Pt+注入剂量为1×1016cm-2,300℃空气氛围中退火得到了最低的接触电阻率,为3.55×10-3Ω·cm2.探讨了Pt+离子注入引起欧姆接触改善的内在机制.     

SIMOX材料的SIMS分析

对ＳＩＭＯＸ材料进行了ＳＩＭＳ深度剖析，研究了电荷积累效应、二次离子传输效率等实验因素对测试结果的影响，氧检测的动态范围达三个量级。对国内、外的ＳＩＭＯＸ材料做了对比研究。     

GaAs中Si的二次离子质谱定量分析

评述砷化镓中硅SIMS定量分析的进展，讨论了相对灵敏度因子法。对此种GaAs的原始参考物质，用实验确认了其可靠性。为常规定量分析研制了二次参考物质。对一些关键实验因素，如样品装载、仪器参数以及离子选择等进行了仔细研究，并评价它们对定量重复性、精确性、检测限和基体效应的影响。Cs 源入射时GaAs中Si定量分析精度在15％内；检测AsSi二次离子时，29Si的检测限达5×1014atoms／cm3。     

光阴极材料GaAs/AlGaAs的组分分析

为探索砷化镓光阴极的光电灵敏度的影响因素 ,利用X射线光电子能谱、二次离子质谱和电化学方法测试和分析了国内和国外GaAs光阴极材料GaAs/AlGaAs的C ,O含量和空穴浓度分布。实验发现 ,国内的材料在GaAs/AlGaAs界面及AlGaAs层的O含量分别为 7 6 %和 10 6 % ,C浓度分别为 5 2×10 18atoms/cm3和 1 0× 10 19atoms/cm3,而国外的材料的O含量相应为 1 0 %和 1 5%。国内的材料GaAs和AlGaAs层的空穴浓度分别为 7× 10 18～ 4× 10 19cm- 3和 8× 10 17cm- 3,而国外材料的相应值分别为 (1 8～ 2 0 )× 10 19cm- 3和 5× 10 18cm- 3。分析认为 ,层中及界面的C ,O杂质偏高和空穴浓度分布不尽合理使光电子扩散长度减小 ,后界面复合增大 ,导致了光电灵敏度下降。     

硅基GaN外延层的SIMS及XPS研究

采用真空反应法在硅基上制备出了GaN外延层。利用二次离子质谱和X射线光电子能谱对GaN外延层进行了深度剖析和表面分析。结果表明 ,外延层中Ga和N分布均匀 ;在表面处Ga发生了偏聚 ;外延层中还存在Si,O等杂质 ,但这些并未影响到GaN外延层的物相及发光性能。实验还表明 ,在外延生长前采用原位清洗可去除Si衬底表面的氧     

二次离子发射的LTE模型及其在GaAs样品中的应用

介绍了二次离子发射的局部热平衡（LTE）模型的发展过程及其在GaAs样品SIMS定量分析中的应用，并尝试了用GaAs基体元素作内标的定量分析方法，取得了较好的结果。     

AlN陶瓷衬底的SIMS和XRD测量

AlN陶瓷中成分与杂质对于AlN的性能具有决定性作用。用二次离子质谱（SIMS）和X射线衍射（XRD）对清华大学材料系电子封装用的AlN陶瓷进行了研究。SIMS谱表明AlN衬底中除Al,N以外还有C，O，Si，Ca，Y等元素，其中有些是表面污染。衬底的SIMS深度分析表明样品O，Ca，Y信号都很强，且分布均匀，说明样品中含有Y2O3，CaO添加剂。AlN样品的XRD谱与AlN的JCPDS卡片对照，在测量范围内卡片上所有峰均出现，且晶面间距符合很好。在XRD谱上找到了与Y2O3和CaO对应的衍射峰。     

Improved microstructure and ohmic contact of Nb electrode on n-type 4H-SiC

Niobium was deposited as an electrode material on an n-type SiC wafer for power device application. The reaction microstructure and electrical contact property were investigated after annealing at 700 to 1000 °C and compared with the results for an Ni electrode. Microstructure-related problems of the Ni electrode could be resolved without sacrificing ohmic contact behavior with a low contact resistivity of 1.53 × 10^− 4 Ω cm². Carbon precipitation was completely eliminated with Nb by the formation of carbides, leading to good adhesion upon wire bonding process. At the reaction interface, Nb₅Si₃ was formed in an epitaxial relationship with SiC, leading to a good interface contact property as well as good interface adhesion.     

Residual surface oxide on ZrV getter—XPS, LEIS and SIMS study

The activated ZrV non-evaporable getter (NEG) film has been studied by means of X-ray photoelectron spectroscopy, low-energy ion scattering and secondary ion mass spectrometry. In this work, we found that the first atomic layer of the thermally activated ZrV NEG consists mainly of zirconium atoms, which are partly oxidized. The residual zirconium suboxides observed on thermally activated ZrV NEG diminish during ion sputtering of NEG surface. It indicates that residual suboxides are located mainly in the top surface layer.     

Thermal-induced intermixing effects on the optical properties of long wavelength low density InAs/GaAs quantum dots

The effect of post-growth rapid thermal annealing on the photoluminescence properties of long wavelength low density InAs/GaAs (001) quantum dots (QDs) with well defined electronic shells has been investigated. For an annealing temperature of 650 °C for 30 s, the emission wavelength and the intersublevel spacing energies remain unchanged while the integrated PL intensity increases. For higher annealing temperature, blue shift of the emission energy together with a decrease in the intersublevel spacing energies are shown to occur due to the thermal activated In–Ga interdiffusion. While, this behaviour is commonly explained as a consequence of the enrichment in Ga of the QDs, the appearance of an additional exited state for annealing temperatures higher than 650 °C suggests a variation of the intermixed QDs's volume/diameter ratio toward QDs's enlargement.     

Enhancement of photoluminescence in Er-doped Ag-SiO2 nanocomposite thin films: A post annealing study

Silver-silica (with Ag 2.8 at.% and 8.7 at.%) nanocomposite (NC) thin films doped with Er⁺³ (0.1-0.9 at.%) were synthesized by atom beam co-sputtering using 1.5 keV Ar atoms. Optical absorption and photoluminescence (PL) studies of pristine and annealed films were performed, together with Rutherford backscattering and secondary ion mass spectroscopy studies for elemental characterization of the NC films. Optical absorption results of pristine and annealed NC film (with Ag ∼8.7 at.%) confirmed the formation of Ag nanoparticles evidenced by the appearance of characteristic surface plasmon resonance absorption features. Photoluminescence (PL) studies, carried out using Ar Laser pumping at 0.488 μm, the wavelength that the Er ions can absorb resonantly, indicated the presence of PL emission around 1.54 μm in the case of all the as-synthesized samples. The observed PL peak corresponds to the atomic transitions of Er as reported in literature. A relative enhancement in the intensity of PL peak has been observed after annealing the NC films. In the case of NC film with 0.9 at.% Er and 8.7 at.% Ag, the enhancement in PL intensity is almost twice, with respect to the as-deposited sample, for a heat treatment of about 1 h at 600 °C in a nitrogen atmosphere. However for a NC film with Er 0.1 at.% + Ag 2.8 at.%, the PL intensity is enhanced by approximately 3.7 times after annealing at 400 °C for 1 h in nitrogen atmosphere. Since the samples with surface plasmon resonance (SPR) did not show the PL enhancement, the role of SPR in the enhancement of the PL is ruled out. The enhanced PL emission from Er and Ag codoped silica indicates that the Er photo-stimulation is mediated by the energy transfer from Ag nanostructures or ions to Er. Lifetimes of PL peaks for the pristine and annealed samples were also studied. The observed lifetime ∼10 ms is a good indication of excellent PL efficiency.