射频磁控溅射生长C轴择优取向AIN压电薄膜

采用射频磁控反应溅射工艺，在Si（400）衬底上制备了高c轴取向的AlN薄膜。用X射线衍射仪（XRD）分析了薄膜特征。研究了不同的Ar／N2比、衬底偏压、工作压强对AlN薄膜c轴择优取向的影响。研究了AlN薄膜在以氮终止的硅衬底和纯净硅衬底两种表面状态的生长机制，发现在以氮终止的硅衬底表面生长的AlN薄膜非常容易得到c轴择优取向的AlN薄膜。     

磁控溅射硅基AlN薄膜的氮-氩气体流量比研究

反应磁控溅射制备AlN薄膜时,薄膜的质量与众多实验参数有关。靶基距、溅射功率、工作气体总压及N2气分压等实验参数影响薄膜质量的报道很多,因此,研究N2/Ar流量比对磁控溅射硅基AlN薄膜元素种类与含量的影响很有实用意义。实验表明,在其他参数一定的情况下,N2/Ar流量比对AlN薄膜元素种类与含量有很大影响。通过实验验证,选择N2/Ar流量比约为1.525可获得高质量的AlN薄膜(100取向)。     

衬底温度对常压MOCVD生长的ZnO单晶膜的性能影响

以H2O作氧源,Zn(C2H5)2作Zn源,N2作载气,在50mm Al2O3(0001)衬底上采用常压MOCVD技术生长出高质量的ZnO单晶薄膜.用X射线双晶衍射、原子力显微镜和光致发光技术对样品进行了综合表征,报道了ZnO单晶膜的(102)非对称衍射结果.研究结果表明,在500～700℃范围内随生长温度升高,ZnO薄膜的双晶摇摆曲线半峰宽增宽,表面粗糙度减小,晶粒尺寸增大,在衬底温度为600℃时生长的ZnO膜的深能级发射最弱.     

衬底温度对常压MOCVD生长的ZnO单晶膜的性能影响

以H2O作氧源,Zn(C2H5)2作Zn源,N2作载气,在50mmAl2O3(0001)衬底上采用常压MOCVD技术生长出高质量的ZnO单晶薄膜.用X射线双晶衍射、原子力显微镜和光致发光技术对样品进行了综合表征,报道了ZnO单晶膜的(102)非对称衍射结果.研究结果表明,在500～700℃范围内随生长温度升高,ZnO薄膜的双晶摇摆曲线半峰宽增宽,表面粗糙度减小,晶粒尺寸增大,在衬底温度为600℃时生长的ZnO膜的深能级发射最弱.     

Si衬底上用反应蒸发法制备AlN单晶薄膜

本文首次报道了在硅衬底上用反应蒸发法沉积AlN薄膜的技术．实验发现在衬底温度为470～850℃的范围内均可得到单晶薄膜，X射线衍射分析表明，薄膜只在2θ=58．9°处出现一个衍射峰，其生长晶面为（1120），是AlN的解理面．在较高的生长温度下，生长速率较低，得到的AlN薄膜具有更窄的衍射半峰宽（0．5°）、Al和N更趋向于化学计量比结合．从扫描电镜测试看出，薄膜表面平整光滑、无裂纹，说明用反应蒸发法外延生长的薄膜表面状况优良．最后，NH3对Si表面的原位清洗也作了一些讨论．     

硅基AlN薄膜制备技术与测试分析

采用直流磁控反应溅射法,在Si(100),Al/Si(100)和Pt/Ti/Si(100)等多种衬底上制备了用于MEMS器件的AlN薄膜.用XRD和AES对薄膜的结构和组分进行了分析,通过优化工艺参数,得到了提高薄膜择优取向的方法,并分析了不同衬底上AlN晶粒生长的有关机理.制备的AlN薄膜显示出良好的〈002〉择优取向性,摇摆曲线的半高宽达到5.6°.     

正晶向SiC衬底上表面光滑的N极性GaN薄膜材料的生长

采用MOCVD技术在101.6 mm(4英寸)正晶向半绝缘C面SiC衬底上生长了厚度为1μm的GaN缓冲层。通过深入研究不同AlN成核层上生长的GaN缓冲层的性质,揭示了正晶向SiC衬底上氮极性GaN的生长机制,发现成核层表面AlN岛的密度是决定缓冲层表面形貌的重要参数,对后续GaN的成核以及GaN岛间的合并具有显著影响。通过在AlN成核层外延期间引入N2作为载气并且以脉冲方式供应铝源,研制的成核层表面成核岛尺寸小且致密性高,有利于促进GaN成核岛之间的横向合并,并抑制GaN缓冲层的岛状生长模式,从而获得了表面光滑的N极性GaN薄膜材料,原子力显微镜20μm×20μm扫描范围下的均方根(rms)粗糙度值为1.5 nm。此外,在表面平滑的GaN薄膜上生长的GaN/AlGaN异质结的电子输运特性也同步得到提升,这有利于N极性GaN材料的微波应用。     

硅基AlN薄膜制备技术与测试分析

采用直流磁控反应溅射法,在Si(100),Al/Si(100)和Pt/Ti/Si(100)等多种衬底上制备了用于MEMS器件的AlN薄膜．用XRD和AES对薄膜的结构和组分进行了分析,通过优化工艺参数,得到了提高薄膜择优取向的方法,并分析了不同衬底上AlN晶粒生长的有关机理．制备的AlN薄膜显示出良好的〈002〉择优取向性,摇摆曲线的半高宽达到5.6°．     

GaN缓冲层上低温生长AlN单晶薄膜

采用电子回旋共振等离子体增强金属有机物化学气相沉积(ECR-PEMOCVD)技术,在α-Al2O3(0001)(蓝宝石)衬底上,分别以高纯氮气(N2)和三甲基铝(TMAl)为氮源和铝源低温生长氮化铝(AlN)薄膜.利用反射高能电子衍射(RHEED)、原子力显微镜(AFM)和X射线衍射(XRD)等测量样品,研究了AlN缓冲层和氮化镓(GaN)对六方AlN外延层质量的影响,实验表明在GaN缓冲层上能够低温生长出C轴取向的AlN单晶薄膜.     

c轴择优取向AlN薄膜的制备研究

采用MOCVD法在蓝宝石(0001)单晶衬底上生长AlN压电薄膜。用XRD和原子力显微(AFM)技术表征薄膜的微观结构。研究了衬底温度、TMA和NH3流量、反应室气压对AlN薄膜织构特性的影响,并对薄膜生长的工艺参数进行了相应优化。结果表明:在优化条件下制备的AlN薄膜高度c轴择优取向,(0002)峰摇摆曲线半高宽仅为0.10°,且薄膜表面平整,椭圆偏振法测出其折射率为2.0～2.4。     

Crystal growth of AlN: Effect of SiC substrate

The morphology of AlN crystal grown under the same growth conditions by the PVT method on four kinds of 4H-SiC substrates (SiC (0001), SiC (000−1), 8° off-axis SiC (0001), and 8° off-axis SiC (000−1), off-oriented from the basal plane toward the 〈11–20〉 direction) was investigated. It is found that the nucleation more easily occurs on the Si face substrate than on the C face substrate at 1800–1900 °C. Hexagonal flakes nucleated on the SiC (0001) substrate, while tetrahedral grains nucleated on the 8° off-axis SiC (0001) substrate. AlN grown on the 8° off-axis SiC (000−1) substrate was strikingly different, and flower pattern structure AlN deposited on the substrate. A stepped structure with smooth terraces was obtained on the 8° off-axis SiC (0001) substrate at 1900 °C for 4 h. We conclude that the AlN grown on the 8° off-axis SiC (0001) substrate was first by island nucleation then by the step-flow growth mode.     

溅射AlN技术对GaN基LED性能的影响

研究了在图形蓝宝石衬底(PSS)上利用磁控溅射制备AlN薄膜的相关技术,随后通过采用金属有机化学气相沉积(MOCVD)在相关AlN薄膜上生了长GaN基LED.通过一系列对比实验,分析了AlN薄膜的制备条件对GaN外延层晶体质量的影响,研究了AlN薄膜溅射前N2预处理功率和溅射后热处理温度对GaN基LED性能的作用机制.实验结果表明:AlN薄膜厚度的增加,导致GaN缓冲层成核密度逐渐升高和GaN外延膜螺位错密度降低刃位错密度升高;N2处理功率的提升会加剧衬底表面晶格损伤,在GaN外延膜引入更多的螺位错;AlN热处理温度的升高粗化了表面并提高了GaN成核密度,使得GaN外延膜螺位错密度降低刃位错密度升高;而这些GaN外延膜位错密度的变化又进一步影响到LED的光电特性.     

The Effect of AlN Nucleation Temperature on the Growth of AlN Films via Metalorganic Chemical Vapor Deposition

AlN epilayers were grown directly on sapphire (0001) substrates using a combined growth scheme, consisting of a low-temperature nucleation layer and a second layer grown by high-temperature pulsed atomic layer epitaxy via metalorganic chemical vapor deposition. With an emphasis on the nucleation layer, its growth temperature was varied from 470°C to 870°C, and obvious differences in the surface morphology, crystal quality, and strain states of the overall AlN epilayers were observed. Based on atomic force microscopy, x-ray diffraction, and Raman spectroscopy results, these differences are ascribed to the nucleation sites and the subsequent grain size. Due to the enhanced mobility of Al adatoms with increasing temperature, the nucleation sites decrease and the subsequent grain size increases, leading to the achievement of atomically flat AlN epilayers with good crystal quality for the nucleation layer grown at 570°C. However, at higher nucleation layer growth temperature, the properties of the AlN epilayers deteriorate due to the possible appearance of misaligned AlN grains. A model is also developed according to all observations.     

PVT法同质籽晶AlN晶体生长

为了获得高质量AlN晶体,通过物理气相传输(PVT)法,采用AlN籽晶进行AlN晶体生长,并通过双温区加热装置对衬底与原料之间的温差进行调节。研究结果表明,籽晶形核阶段,随着AlN籽晶与原料顶温差的减小,AlN的形核机制呈现三种模式,分别为岛生长模式、畴生长模式和螺旋位错生长模式;晶体生长阶段,通过增加AlN籽晶与原料顶温差来提高晶体生长速率,采用10℃/h的变温速率将温差从10℃增加为30℃时,AlN晶体生长模式不变,仍然保持螺旋位错生长模式,该生长模式下获得的AlN晶体结晶质量最高,(0002)面摇摆曲线半峰宽(FWHM)约为55 arcsec。     

Growth rate and surface microstructure in α(6H)–SiC thin films grown by chemical vapor deposition

Monocrystalline 6H-SiC thin films have been epitaxially grown on off-axis 6H-SiC {0001} substrates in the temperature range of 1623–1873 K via chemical vapor deposition. The growth rate was a strong function of the growth temperature and the reactant gas concentration. The activation energies for growth were 64 kJ/mole and 55 kJ/mole for the (0001) Si face and the (0001) C face, respectively. The concentration of growth pits in the films increased as a function of decreasing deposition temperature, increasing concentration of reactant gases and increasing off-axis orientation. Beta-SiC islands were also observed in the epilayers when the (SiH₄ + C₂H₄)/H₂ ratio was ≥2.5:3000.     

使用溅射AlN成核层实现大规模生产深紫外LED

高质量AlN薄膜对制造高性能深紫外器件非常重要,但是目前还很难使用大型工业MOCVD生长出高质量的AlN薄膜.采用磁控溅射制备了不同厚度的用作成核层的AlN薄膜,使用大型工业MOCVD直接在成核层上高温生长AlN外延层,研究了不同成核层对AlN外延层质量的影响.通过扫描电子显微镜和原子力显微镜对成核层AlN薄膜的表面形貌进行表征;使用高分辨X射线衍射仪对AlN外延层晶体质量进行表征,结果表明:在溅射成核层上生长的AlN外延层的晶体质量有显著提高.使用大型工业MOCVD在蓝宝石衬底上成功制备出中心波长为282 nm的可商用深紫外LED,在注入电流为20 mA时,单颗深紫外LED芯片的光输出功率达到了1.65 mW,对应的外量子效率为1.87%,饱和光输出功率达到4.31 mW.     

Analysis of reactor geometry and diluent gas flow effects on the metalorganic vapor phase epitaxy of AIN and GaN thin films on α(6H)-SiC substrates

The influence of diluent gas on the metalorganic vapor phase epitaxy of AlN and GaN thin films has been investigated. A computational fluid dynamics model using the finite element method was employed to improve film uniformity and to analyze transport phenomena. The properties of AlN and GaN thin films grown on α(6H)-SiC(0001) substrates in H₂ and N₂ diluent gas environments were evaluated. Thin films of AlN grown in H₂ and N₂ had root mean square (rms) roughness values of 1.5 and 1.8 nm, respectively. The surface and defect microstructures of the GaN thin films, observed by scanning and transmission electron microscopy, respectively, were very similar for both diluents. Low temperature (12K) photoluminescence measurements of GaN films grown in N₂ had peak intensities and full widths at half maximum equal to or better than those films grown in H₂. A room temperature Hall mobility of 275 cm²/V·s was measured on 1 μm thick, Si-doped, n-type (1×10¹⁷ cm⁻³) GaN films grown in N₂. Acceptor-type behavior of Mg-doped GaN films deposited in N₂ was repeatably obtained without post-growth annealing, in contrast to similar films grown in H₂. The GaN growth rates were ∼30% higher when H₂ was used as the diluent. The measured differences in the growth rates of AlN and GaN films in H₂ and N₂ was attributed to the different transport properties of these mixtures, and agreed well with the computer model predictions. Nitrogen is shown to be a feasible alternative diluent to hydrogen for the growth of AlN and GaN thin films.     

GaN薄膜表面形貌与AlN成核层生长参数的关系

采用金属有机物化学气相淀积技术生长了以AlN为成核层的GaN薄膜,研究了成核层生长时三甲基铝(TMAl)流量对最终GaN薄膜表面形貌的影响.研究结果表明,高质量GaN薄膜只能在高TMAl流量下获得,采用充足的TMAl源才能形成满足需要的AlN成核点,这是生长高质量GaN薄膜的一个先决条件.     

Thermal conductivity of AlN thin films deposited by RF magnetron sputtering

Aluminum nitride (AlN) film, which is being investigated as a possible passivation layer in inkjet printheads, was deposited on a Si (1 0 0) substrate at 400 °C by radio frequency (RF) magnetron sputtering using an AlN ceramic target. Dependence on various reactive gas compositions (Ar, Ar:H₂, Ar:N₂) during sputtering was investigated to determine thermal conductivity. The crystallinity, grain size, and Al–N bonding changes by the gas compositions were examined and are discussed in relation to thermal conductivity. Using an Ar and 4% H₂, the deposited AlN films were crystalline with larger grains. Using a higher nitrogen concentration of 10%, a near amorphous phase, finer morphology, and an enhanced Al–N bonding ratio were achieved. A high thermal conductivity of 134 W/mk, which is nine times higher than that of the conventional Si₃N₄ passivation film, was obtained with a 10% N₂ reactive gas mixture. A high Al–N bonding ratio in AlN film is considered the most important factor for higher thermal conductivity.     

Raman scattering of polycrystalline 3C-SiC film deposited on AlN buffer layer by using CVD with HMDS

This paper presents the Raman scattering characteristics of poly (polycrystalline) 3C-SiC thin films deposited on AlN buffer layer by atmospheric pressure chemical vapor deposition (APCVD) using hexamethyldisilane (MHDS) and carrier gases (Ar+H₂). The Raman spectra of SiC films deposited on AlN layer of before and after annealing were investigated according to the growth temperature of 3C-SiC. Two strong Raman peaks, which mean that poly 3C-SiC admixed with nanoparticle graphite, were measured in them. The biaxial stress of poly 3C-SiC/AlN was calculated as 896 MPa from the Raman shifts of 3C-SiC deposited at 1180 °C on AlN of after annealing.