GaAs表面旋转超声雾化清洗新技术

研究了一种新型湿法化学清洗半导体GaAs表面的方法。通过简单设计清洗工艺能使GaAs表面产生最低的损伤。GaAs表面清洗必须满足三个条件：(1)清除热力学不稳定因素和表面粘附的杂质,(2) 除去GaAs表面氧化层,(3)提供一个光滑平整的GaAs表面。本文采用旋转超声雾化方式用有机溶剂除去GaAs表面的杂质,再用NH4OH:H2O2:H2O= 1:1:10和HCl:H2O2:H2O=1:1:20顺次腐蚀非常薄的GaAs层,去除表面的金属污染,并在GaAs表面形成一个非常薄的氧化层表面,最后用NH4OH:H2O= 1:5溶液来清除GaAs表面氧化层。测试GaAs表面的特性,分别用X射线光电光谱仪、X射线全反射荧光光谱仪和原子力显微镜测试了GaAs表面氧化的组分、GaAs表面金属污染和GaAs表面形貌,测试结果表明通过旋转超声雾化技术清洗可提供表面无杂质污染、金属污染和表面非常光滑的GaAs衬底,以供外延生长。     

高质量InAs单晶材料的制备及其性质

利用液封直拉法(LEC)生长了直径50mm〈100〉和〈111〉晶向的InAs单晶.分析研究了n型杂质Sn,S和p型杂质Zn,Mn的分凝特性、晶格硬化作用、掺杂效率等.利用X射线双晶衍射分析了晶体的完整性.对InAs晶片的抛光、化学腐蚀和清洗进行了分析,在此基础上实现了抛光晶片的开盒即用(EPI-READY).     

高质量InAs单晶材料的制备及其性质

利用液封直拉法(LEC)生长了直径50mm〈100〉和〈111〉晶向的InAs单晶.分析研究了n型杂质Sn,S和p型杂质Zn,Mn的分凝特性、晶格硬化作用、掺杂效率等.利用X射线双晶衍射分析了晶体的完整性.对InAs晶片的抛光、化学腐蚀和清洗进行了分析,在此基础上实现了抛光晶片的开盒即用(EPI-READY).     

用于红外探测的短周期InAs/GaSb超晶格材料的生长

用金属有机物化学气相淀积法(MOCVD)在GaSb衬底上生长InAs/GaSb超晶格,探索了最佳的生长厚度,优化了各种生长参数,并且分析了源流量控制的重要性.得到的超晶格材料的光致发光(PL)谱、X射线双晶衍射图以及表面形貌图表明,生长的超晶格材料可以响应10μm的长波,且具有良好的表面形貌和外延层质量.     

梯度掺杂结构GaN光电阴极表面的净化

对梯度掺杂结构GaN阴极表面进行了化学清洗,清洗后利用X射线光电子能谱仪(XPS)分析了阴极表面,分析表明化学清洗能有效去除阴极表面的油脂和加工中残存的无机附着物;然后在超高真空室内710℃下对阴极进行了高温退火清洁,去除化学清洗后残留在阴极表面的C、O等吸附物,使阴极表面达到制备高性能负电子亲和势(NEA)光电阴极所需的原子级清洁程度。最后通过阴极激活实验加以验证,结果证实化学处理后热退火方法能有效净化梯度掺杂结构GaN阴极表面。     

硅衬底化学机械抛光后去除有机物残留的研究

化学机械抛光后,Si片表面残留有机物会影响清洗的综合效果,并会造成器件失效。针对上述问题提出了一种新的清洗方案,用金刚石膜电化学法制备氧化性强的过氧焦磷酸盐溶液,可有效氧化分解表面有机沾污,配合FA/O I型活性剂溶液进行预清洗,去除表面颗粒的同时降低了表面粗糙度。此外,过氧焦磷酸盐被还原成的焦磷酸盐具有很强的络合力,它能与Cu等金属离子络合,达到同时去除金属杂质的目的。研究了氧化液的体积分数对有机物清洗效果的影响,发现氧化液的体积分数为60%～100%时残留有机物去除效果最佳。作为一种新型的清洗方法,清洗效率高且成本低,操作简单可控且环保,符合新时期半导体清洗工艺的要求。     

新型半导体清洗剂的清洗工艺

报道了利用红外吸收谱、X射线光电子谱和表面张力测试仪对新型半导体清洗工艺进行研究的结果.采用DGQ系列清洗剂清洗硅片时,首先需用HF稀溶液浸泡硅片,以利于将包埋于氧化层内的金属和有机污染物去除;溶液的配比浓度由临界胶束浓度和硅片表面的污染程度确定,要确保清洗过程中溶液内部有足够的胶束存在,一般DGQ -1、DGQ-2的配比浓度在90%到98%之间;当温度接近表面活性剂溶液的浊点温度时,增溶能力最强,因而清洗液的温度定在60℃.     

新型半导体清洗剂的清洗工艺

报道了利用红外吸收谱、X射线光电子谱和表面张力测试仪对新型半导体清洗工艺进行研究的结果.采用DGQ系列清洗剂清洗硅片时,首先需用HF稀溶液浸泡硅片,以利于将包埋于氧化层内的金属和有机污染物去除;溶液的配比浓度由临界胶束浓度和硅片表面的污染程度确定,要确保清洗过程中溶液内部有足够的胶束存在,一般DGQ -1、DGQ-2的配比浓度在90%到98%之间;当温度接近表面活性剂溶液的浊点温度时,增溶能力最强,因而清洗液的温度定在60℃.     

InAs基InAs/Ga（As）Sb II类超晶格长波红外探测器湿法腐蚀研究

开展了InAs基InAs/Ga（As）Sb II类超晶格长波红外探测器的湿法腐蚀工艺研究.选择的腐蚀液由柠檬酸、磷酸和过氧化氢组成,先后在InAs、GaSb体材料和InAs/Ga（As）Sb II类超晶格上进行了湿法腐蚀实验,分别获得了其最佳的腐蚀液组分及配比.使用优化的磷酸系腐蚀液对InAs/Ga（As）Sb II类超晶格进行腐蚀,获得的腐蚀表面粗糙度仅为1 nm.然后使用改进的工艺制备了50 ％截止波长为12 μm的超晶格长波单元器件,实验结果表明磷酸系腐蚀液可以获得低暗电流密度的InAs基InAs/Ga（As）Sb II类超晶格长波红外探测器.另外,在81 K下,该探测器的表面电阻率（ρ_Surface）为4.4 × 10³ Ωcm.     

退火温度对ZnO薄膜结构和发光性能的影响

采用常压金属有机物化学气相淀积法在(0001)Al2O3衬底上生长出高质量ZnO单晶膜,在空气中进行了710～860℃不同温度的退火处理．用X射线双晶衍射、光致发光法研究了退火温度对ZnO薄膜的结构、发光性能的影响．ZnO（002）面X射线双晶ω扫描曲线的半高宽(FWHM) 随退火温度的升高变小,770℃后基本保持不变,ZnO（102）面双晶ω扫描曲线的FWHM一直变小．770℃退火后ZnO样品X射线ω-2θ扫描曲线中出现ZnO2（200）衍射峰．同时,光致发光测试表明,随着退火温度升高,带边发光强度减弱,与深能级有关的绿带发光出现并逐渐增强．通过ICP刻蚀,去除退火后样品的表面层,ω-2θ扫描曲线中ZnO2（200）衍射峰和PL谱中绿带发光均消失,表明ZnO2相和深能级缺陷在样品表面．     

Modeling InAs/GaSb and InAs/InAsSb Superlattice Infrared Detectors

InAs/GaSb and InAs/InAsSb type II superlattices have been proposed as promising alternatives to HgCdTe for the photon-absorbing layer of an infrared detector. When combined with a barrier layer based on an InAs/AlSb superlattice or an AlSbAs alloy, respectively, they can be used to make diffusion-limited “barrier” detectors with very low dark currents. In this work we compare theoretical simulations with experimental bandgap and photoabsorption data for such superlattices, spanning from the mid to the long-wave infra-red (2.3–12 μm). The spectral response of detectors based on these materials is also simulated. The simulations are based on a version of the k · p model developed by one of the authors, which takes interface contributions and bandgap bowing into account. Our results provide a way of assessing the relative merits of InAs/GaSb and InAs/InAsSb superlattices as potential detector materials.     

Cyclotron resonance of dirac fermions in InAs/GaSb/InAs quantum wells

The band structure of three-layer symmetric InAs/GaSb/InAs quantum wells confined between AlSb barriers is analyzed theoretically. It is shown that, depending on the thicknesses of the InAs and GaSb layers, a normal band structure, a gapless state with a Dirac cone at the center of the Brillouin zone, or inverted band structure (two-dimensional topological insulator) can be realized in this system. Measurements of the cyclotron resonance in structures with gapless band spectra carried out for different electron concentrations confirm the existence of massless Dirac fermions in InAs/GaSb/InAs quantum wells.     

Photoconductivity of InAs/GaAs structures with InAs nanoclusters in the near-infrared region

InAs/GaAs multilayered heterostructures containing dense arrays of the low-defect partially relaxed InAs nanoclusters larger than defect-free quantum dots are fabricated by metal-organic chemical vapor deposition in an atmospheric-pressure reactor. The structures have intense photoconductivity in the wavelength range of 1–2 μm at room temperature. The detectivity of fabricated prototypes of photodetectors is D* = 10⁹ cm Hz^1/2 W⁻¹. The relaxation time of photoconductivity at a wavelength of 1.5 μm is less than 10 ns.     

High-transconductance delta-doped InAs/AlSb HFETs with ultrathinsilicon-doped InAs quantum well donor layer

Modulation-doping of InAs/AlSb quantum wells generally requires the use of chalcogenide donor impurities because silicon, the usual donor of choice in MBE, displays an amphoteric behavior in antimonide compounds. In this letter, we demonstrate the use of an ultrathin 9 Å silicon doped InAs well to delta-dope the current-carrying InAs channel of an InAs/AlSb heterostructure field-effect transistor (HFET). Using this new approach, we have fabricated delta-doped 0.6-μm gate InAs/AlSb HFETs with a measured extrinsic transconductance of 800 mS/mm at V_DS=0.8 V, a cutoff frequency f_T=60 GHz (F_MAX=87 GHz), and well-behaved I-V curves. HFET's with a 2-μm gatelength also feature very high transconductances in the 700-800 mS/mm range at V_DS=1.5 V. The present work eliminates the requirement for chalcogenide compound donor sources to delta-dope InAs/AlSb quantum wells by allowing the use of silicon in the fabrication of high-performance InAs/AlSb HFET's     

InAs/GaAs自组装量子点结构的能带不连续量

为确定异质结界面带阶,结合光致发光(PL)谱和深能级瞬态谱(DLTS)测量结果,利用有效质量近似理论,计算得到了InAs/GaAs自组装量子点结构的能带不连续量,其中导带不连续量ΔEc＝0.97 eV,价带不连续量ΔEv＝0.14 eV.     

An InAlAs/InAs MODFET

An InAs modulation-doped field-effect transistor (MODFET) using an epitaxial heterostructure based entirely on arsenides is reported. The heterostructure was grown by MBE on InP and contains a 30-Å InAs channel. A 2-μm-gate-length device displays well-behaved characteristics, showing sharp pinch-off (V_th=0.8 V) and small output conductance (5 mS/mm) at 300 K. The maximum transconductance is 170 mS mm with a maximum drain current of 312 mA/mm. Strong channel quantization results in a breakdown voltage of -9.6 V, a severalfold improvement over previous InAs MODFETs based on antimonides. Low-temperature magnetic field measurements show strong Shubnikov-de Haas oscillations which, over a certain range of gate voltage, strongly indicate that the electron channel resides in the InAs layer     

Ultra-low density InAs quantum dots

We show that InAs quantum dots (QDs) can be grown by molecular beam epitaxy (MBE) with an ultralow density of sin 10⁷ cm^?2 without any preliminary or post-growth surface treatment. The strain-induced QD formation proceeds via the standard Stranski-Krastanow mechanism, where the InAs coverage is decreased to 1.3–1.5 monolayers (MLs). By using off-cut GaAs (100) substrates, we facilitate the island nucleation in this subcritical coverage range without any growth interruption. The QD density dependences on the InAs coverage are studied by photoluminescence, atomic force microscopy, transmission electron microscopy, and are well reproduced by the universal double exponential shapes. This method enables the fabrication of InAs QDs with controllable density in the range 10⁷–10⁸ cm^?2, exhibiting bright photoluminescence.     

InP基InAlAs-InAs HEMT

对ＩｎＡｓ沟道ＩｎＡｌＡｓ－ＩｎＡｓ高电子迁移率晶体管材料及器件的设计和器件制作工艺进行了研究，器件样品性能良好，１μｍ栅长ＩｎＡｌＡｓ－ＩｎＡｓＨＥＭＴ器件的最大跨导３００Ｋ时达到２５０ｍＳ／ｍｍ。这是国内首次研制成功的ＩｎＡｓ沟道ＨＥＭＴ器件。