硅烷外延淀积多晶硅

SiH_4-H_2-HCl系统用于淀积多晶硅膜,有着SiCl_4外延无法比拟的优越性,其生长温度最佳值在1050℃,生长速度从实验趋势上来看远远超过了SiCl_4外延.外延质量也比SiCl_4外延好.所以,在一些特殊器件的制造中采用本系统是完全必要的.     

低温低真空CVD生长锗硅异质结外延材料

利用自行研制的超净低温低真空化学气相外延系统,应用锗烷和硅烷气本,在２英雨到３英雨的衬底硅片上生长了锗硅异质结外延层。在６６５℃,６１０℃和５７５℃不同温度分别生长了Ｓｉ０．５Ｇｅ０．２,Ｇｅ０．５和Ｓｉ０．６５Ｇｅ０．３５的异质外延层,获得了原子级表面和界面的异质外延材料。结果表明：外延生长速率和Ｇｅ组分由硅烷和锗烷的分压及生长时的温度控制。并利用Ｘ射线双昌衍射,扩展电阻和电化学Ｃ－Ｖ法研究了Ｇ     

RRH/VLP-CVD低温外延硅薄膜的电学性质

本文对低温外延新技术——“快速辐射加热、超低压化学气相淀积”(RRH/VLP-CVD)生长的外延硅薄膜的电学性质进行了分析研究.扩展电阻分析显示了外延层杂质浓度分布均匀,与衬底间的界面区杂质分布陡峭.在外延层上制备了霍耳样品、PN结二极管和Al-SiO_2-SiMOS结构,经测量分析所得各项重要数据与优质硅单晶所制的样品相一致.实验结果表明RRH/VLP-CVD低温外延硅薄膜具有良好的电学性质,已可用于器件的制备.     

MOCVD生长高Al组分AlGaN材料研究

报道了用MOCVD在蓝宝石衬底上生长日盲型AlGaN基紫外探测器用的高质量AlN、AlGaN材料。通过优化AlN、AlGaN生长的工艺条件,如生长温度、生长压力及Ⅴ/Ⅲ比等,得到了器件级高质量的AlN、AlGaN外延材料。AlN外延膜X射线双晶衍射ω(002)面扫描曲线半高宽为97",ω(102)面扫描曲线半高宽为870",Al0.6Ga0.4N外延膜双晶衍射ω(002)面扫描曲线半高宽为240";使用原子力显微镜(AFM)对两种样品5μm×5μm区域的表面平整度进行了表征,AlN外延膜的粗糙度(Rms)为8.484nm,Al0.6Ga0.4N外延膜的粗糙度为1.104nm;透射光谱测试显示AlN和Al0.6Ga0.4N吸收带边分别为205nm和266nm,且都非常陡峭。     

肖特基器件用重掺As衬底上外延层过渡区控制

掺As衬底外延片很大部分用于肖特基器件,器件对正向压降要求越来越高,因此对外延层参数之一的过渡区宽度提出了更高要求.讨论了影响过渡区的温度、生长速率、本征CAP层以及赶气等因素.通过一系列实验,找到了合理的生长条件,得到了完美的过渡区,解决了器件反向电压和正向压降之间的矛盾.在反向电压一致的条件下,正向压降平均降低了200 mV,产品整体成品率提高了两个百分点以上.研究结果已成功应用于大规模生产中.     

隧道带间级联双波长可见光半导体激光器制备

利用金属有机物化学汽相淀积(MOCVD)一次外延生长了含有2个有源区的隧道带间级联双波长可见光半导体激光器(LD)材料。其隧道结为GaAs。2个有源区分别为AlGaAs单量子阱和GaInP多量子阱。SEM照片表明,材料生长质量良好。用生长的材料制备了双沟深腐蚀结构F P腔激光器。器件的阈值电流为177mA,未镀膜时的单面斜率效率为1.3W/A,远场为单瓣,垂直和水平方向的发散角分别为8°和34°。在输出光功率为100mW时,2个激射波长分别为699nm和795nm,与PL测试结果相一致。     

MOCVD技术

金属有机物化学气相淀积(Metal Organic Chemical Vapor Deposition, 简称 MOCVD)自 20 世纪 60 年代首次提出以来,经过 70 年代至 80 年代的发展,90 年代已经成为砷化镓、磷化铟等光电子材料外延片制备的核心生长技术,特别是制备氮化镓发光二极管和激光器外延片的主流方法。到目前为止,从生长的氮化镓外延片和器件的性能以及生产成本等主要指标来看还没有其它方法能与之相比。MOCVD技术     

GaN基材料及其外延生长技术研究

介绍了GaN基材料的基本特性、三种主要外延生长技术（MOCVD、MBE、HVPE）、衬底材料的选择及缓冲层技术;分析得出目前存在的GaN体单晶技术不完善、外延成本高、衬底缺陷及接触电阻大等主要问题制约了研究的进一步发展;指出今后的研究重点是完善GaN体单晶材料的生长工艺,以利于深入研究GaN的物理特性及有效地解决衬底问题,研究缓冲层的材料、厚度、组分等以提高GaN薄膜质量。     

GaN基材料及其外延生长技术研究

介绍了GaN基材料的基本特性、三种主要外延生长技术(MOCVD、MBE、HVPE)、衬底材料的选择及缓冲层技术;分析得出目前存在的GaN体单晶技术不完善、外延成本高、衬底缺陷及接触电阻大等主要问题制约了研究的进一步发展;指出今后的研究重点是完善GaN体单晶材料的生长工艺,以利于深入研究GaN的物理特性及有效地解决衬底问题,研究缓冲层的材料、厚度、组分等以提高GaN薄膜质量。     

氧气放电辅助激光淀积原位制备高T_c超导薄膜

采用低压氧气放电辅助的激光淀积方法,原位外延生长出零电阻温度91K,临界电流密度10~5A/cm~2的Y-Ba-Cu-O高温超导薄膜。扫描电镜和X光衍射分析结果表明,薄膜中超导相晶粒的生长具有c轴垂直于表面的择优取向。     

A comparison of ethyl iodide and hydrogen chloride for doping ZnSe grown by photoassisted MOVPE

We have conducted a study of the electrical and photoluminescence properties of ZnSe films grown by photoassisted metalorganic vapor phase epitaxy (MOVPE) (250 Torr, 400°C) with ethyl iodide and hydrogen chloride as n-type dopant sources. A higher peak electron concentration and a lower minimum resistivity were observed using hydrogen chloride (5.4 × 10¹⁸ cm⁻³, and .0070 ohm-cm, respectively), as opposed to ethyl iodide (1.55 × 10¹⁷ cm ⁻³, and 0.067 ohm-cm, respectively). We show that the higher electron concentrations observed in the chlorine doped layers are due to a higher incorporation of chlorine atoms than that of iodine atoms, and that this may be a result of the different tetrahedral misfit factors for these atoms. Our photoluminescence and 77K Hall effect data support this conclusion. Growth rate depression was observed to be more severe for iodine doped layers than for chlorine doped layers. Thus, it appears that hydrogen chloride is a superior dopant source for low-temperature photoassisted MOVPE ZnSe growth of n-type layers for blue-green laser diodes in the pressure-temperature regime investigated.     

Graphene‐Assisted Epitaxy of Nitrogen Lattice Polarity GaN Films on Non‐Polar Sapphire Substrates for Green Light Emitting Diodes

Lattice polarity is a key point for hexagonal semiconductors such as GaN. Unfortunately, only Ga‐polarity GaN have been achieved on graphene till now. Here, the epitaxy of high quality nitrogen‐polarity GaN films on transferred graphene on non‐polar sapphire substrates by molecular beam epitaxy is reported. This success is achieved through atomic nitrogen irradiation, where C? N bonds are formed in graphene and provide nucleation sites for GaN and leading to N‐polarity GaN epitaxy. The N‐polarity characteristics are confirmed by chemical etching and transmission electron microscopy measurement. Due to the higher growth temperature of InGaN at N‐polarity than that at Ga‐polarity, green light emitting diodes are fabricated on the graphene‐assisted substrate, where a large redshift of emission wavelength is observed. These results open a new avenue for the polarity modulation of III‐nitride films based on 2D materials, and also pave the way for potential application in longer wavelength light emitting devices.     

红外探测器材料和HgCdTe材料的发展现状

简要介绍了主要的红外探测器材料,包括半导体光电探测器材料,热释电材料和热敏电阻材料,回顾了ＨｇＣｄＴｅ材料的发展历史和现状,液相外延,分子束外延和金属有机物汽相外延是目前生长ＨｇＣｄＴｅ薄膜的３种主要技术,作者认为,薄膜材料是今后红外探测器材料的主要研究课题。     

MEE生长参数对复合衬底材料质量的影响

Si基CdTe中ZnTe缓冲层的生长影响着材料表面粗糙度和半峰宽。本文为了验证分子束外延Si基CdTe中采用迁移增强外延(MEE)技术生长的ZnTe缓冲层的生长参数对复合衬底材料表面粗糙度和半峰宽的影响,对涉及到的MEE生长过程中的主要参数包括：Zn与Te数值比、MEE生长温度、Zn与Te束流强度值进行研究,设计了三组实验,并使用高分辨X光衍射仪、白光干涉仪和红外傅里叶光谱仪测试外延薄膜生长结果,总结MEE生长参数对复合衬底材料质量影响,通过实验得到最优的外延工艺条件,提高材料质量。     

The photoassisted MOVPE growth of ZnSSe using tertiary-butylmercaptan

We have conducted a study of the compositional control of epitaxial ZnS_ySe_1-y grown by photoassisted metal organic vapor phase epitaxy (MOVPE) (250 torr, 340°C, UV=14 mW/cm²) on GaAs (100) substrates. We have achieved lattice matched ZnSSe films on GaAs substrates using photoassisted growth using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butylmercaptan (t-BuSH) as precursors. In addition, we have obtained sulfur compositions (y), ranging from 0.023 to unity (ZnS). The growth rate of the ZnS was 1 μm/h, which was previously unattainable by our group using diethylsulfur. The closely lattice matched sample (y=0.07 as determined by high resolution x-ray diffraction) showed a near band edge peak intensity (NBE) to deep level emission intensity (DLE) ratio of 77 to 1, as determined by room temperature photoluminescence measurements. We have examined the sulfur incorporation as a function of source mole fractions, UV intensity, and growth temperature and found that optimized growth conditions (optimized for range of compositions possible, and NBE/DLE ratio) are X_DMZn=1.5 × 10⁻⁴, X_DMSe=3×10⁻⁴, UV=14 mW/cm², growth temperature=340°C. X_DMZn and X_DMSe are the mole fractions of DMZn and DMSe, respectively. We have found the growth rate to be 1 μm/h for y=0.023 to 0.24 for these optimized conditions. It was found that to achieve sulfur compositions of less than 0.9, the t-BuSH mole fractions had to be kept low. Higher UV intensities increased the incorporation of selenium, while also lowering the material quality (NBE/DLE ratios). We have shown that the optical material qualities of ZnSSe films grown with t-BuSH are much better than ZnSSe films grown with DES.     

化学束外延及其在半导体材料与器件中的应用

本文介绍了薄膜晶体生长的最新技术--化学束外延(CBE),通过与分子束外延(MBE)和金属有机化学汽相沉积(MOCVD)技术的比较,说明了这一新技术的基本概念,生长动力学以及在半导体材料和激光器件方面的应用.     

GaN/GaAs(001)与GaN/Al2O3(0001)外延层光辅助湿法腐蚀行为的比较

研究了用金属有机物气相外延(MOVPE)方法在GaAs(001)衬底上生长的立方相GaN(c-GaN)外延层的光辅助湿法腐蚀特性,并和生长在蓝宝石(0001)衬底上的六方相GaN(h-GaN) 外延层的光辅助湿法腐蚀特性进行了比较.实验发现c-GaN膜的暗态电流和光电流的变化不同于h-GaN膜的腐蚀电流的变化规律.对引起上述差异的原因进行了简单的讨论.     

Structural properties of ZnSy Se1−yZnSe/GaAs (001) heterostructures grown by photoassisted metalorganic vapor phase epitaxy

ZnS_ySe_1−yZnSe/GaAs (001) heterostructures have been grown by photoassisted metalorganic vapor phase epitaxy, using the sources dimethylzinc, dimethylselenium, diethylsulfur, and irradiation by a Hg arc lamp. The solid phase composition vs gas phase composition characteristics have been determined for ZnSy_ySe_1−y grown with different mole fractions of dimethylselenium and different temperatures. Although the growth is not mass-transport controlled with respect to the column VI precursors, the solid phase composition vs gas phase composition characteristics are sufficiently gradual so that good compositional control and lattice matching to GaAs substrates can be readily achieved by photoassisted growth in the temperature range 360°C ≤ T ≤ 400°C. ZnSe/GaAs (001) single heterostructures were grown by a two-step process with ZnSe thicknesses in the range from 54 nm to 776 nm. Based on 004 x-ray rocking curve full width at half maximums (FWHMs), we have determined that the critical layer thickness is h_c ≤200 nm. Using the classical method involving strain, lattice relaxation is undetectable in layers thinner than 270 nm for the growth conditions used here. Therefore, the rocking curve FWHM is a more sensitive indicator of lattice relaxation than the residual strain. For ZnS_ySe_1−y layers grown on ZnSe buffers at 400°C, the measured dislocation density-thickness product Dh increases monotonically with the room temperature mismatch. Lower values of the Dh product are obtained for epitaxy on 135 nm buffers compared to the case of 270 nm buffers. This difference is due to the fact that the 135 nm ZnSe buffers are pseudomorphic as deposited. For ZnS_ySe_1−y layers grown on 135 nm ZnSe buffers at 360°C, the minimum dislocation density corresponds approximately to room-temperature lattice matching (y ∼ 5.9%), rather than growth temperature lattice matching (y ∼ 7.6%). Epitaxial layers with lower dislocation densities demonstrated superior optical quality, as judged by the near-band edge/deep level emission peak intensity ratio and the near band edge absolute peak intensity from 300K photoluminescence measurements.     

High Efficiency Perovskite Solar Cells Exceeding 22% via a Photo-Assisted Two-Step Sequential Deposition

One of the most effective methods to achieve high-performance perovskite solar cells (PSCs) is to employ additives as crystallization agents or to passivate defects. Tri-iodide ion has been known as an efficient additive to improve the crystallinity, grain size, and morphology of perovskite films. However, the generation and control of this tri-iodide ion are challenging. Herein, an efficient method to produce tri-iodide ion in a precursor solution using a photoassisted process for application in PSCs is developed. Results suggest that the tri-iodide ion can be synthesized rapidly when formamidinium iodide (FAI) dissolved isopropyl alcohol (IPA) solution is exposed to LED light. Specifically, the photoassisted FAI–IPA solution facilitates the formation of fine perovskite films with high crystallinity, large grain size, and low trap density, thereby improving the device performance up to 22%. This study demonstrates that the photoassisted process in FAI dissolved IPA solution can be an alternative strategy to fabricate highly efficient PSCs with significantly reduced processing times.