Si衬底上侧向外延生长GaN的研究

采用条形Al掩模在Si(111)衬底上进行了GaN薄膜侧向外延的研究.结果显示,当掩模条垂直于Si衬底[11-2]方向,也即GaN[10-10]方向时,GaN无法通过侧向生长合并得到表面平整的薄膜;当掩模条平行于Si衬底[11-2]方向,也即GaN[10-10]方向时,GaN侧向外延速度较快,有利于合并得到平整的薄膜.同时,研究表明,升高温度和降低生长气压都有利于侧向生长.通过优化生长工艺,在条形Al掩模Si(111)衬底上得到了连续完整的GaN薄膜.原子力显微镜测试显示,窗口区域生长的GaN薄膜位错密度约为1×109/cm2,而侧向生长的GaN薄膜位错密度降低到了5×107/cm2以下.     

Coalescence of InP Epitaxial Lateral Overgrowth by MOVPE with V/III Ratio Variation

The effects of V/III ratio and seed window orientation on the coalescence of epitaxial lateral overgrowth InP over SiO₂ using metal organic vapor-phase epitaxy with tertiary butyl phosphine were investigated. Parallel lines having θ = 60° and 30° off [0[`1] \bar{1} 1] were coalesced, and their lateral growth rate variation with V/III was measured. Coalescence of lines separated by narrow angles in a star-like pattern was also studied. We find the greatest extent of coalescence to occur when the window stripe is oriented just off of the ⟨010⟩ directions. V/III ratio strongly affects the extent of coalescence, showing an alternating enhancement or inhibition depending on which side of the ⟨010⟩ direction the stripes are oriented. The variation in quality of coalesced material between stripes separated by narrow angles is examined with cross-sectional transmission electron microscopy, illustrating the most problematic growth directions under two V/III ratio conditions.     

MOCVD侧向外延生长GaN的研究

在低压金属有机化学气相沉积(LP-MOCVD)系统中利用侧向外延生长(epitaxial lateral overgrowth,ELO)技术进行了二次外延GaN的研究.SEM观察结果表明,翼区和窗口区宽度比值不同的图形衬底,侧向和纵向的生长速率不同;其AFM表面形貌图像表明,长平的ELO-GaN表面平整,位错密度较低.ELO-GaN的光致发光(PL)谱的带边峰比传统方法生长的GaN的带边峰红移了14.0 meV,表明ELO-GaN的应力得到部分释放,晶体质量提高.ELO-GaN和普通外延GaN的拉曼散射谱比较表明,ELO-GaN中的应力较小,晶体质量较高,A1(TO)模的出现说明其晶轴取向相对于(0001)方向发生微小的偏移.     

MOCVD法侧向外延生长高质量GaN

利用金属有机物气相外延法(MOCVD),在GaN/蓝宝石复合衬底上,采用侧向外延生长技术制备出高质量的GaN外延膜,并对其进行扫描电镜、X射线双晶衍射、透射电镜测量和分析.发现完全合并后的GaN外延层的表面平整,晶体质量较衬底有大幅的提高,透射电镜进行微区位错观察发现窗口区穿透位错大部分发生转向,侧向生长区下方的穿透位错被掩膜阻断.     

蓝宝石上横向外延GaN薄膜

在蓝宝石衬底上利用金属有机物气相外延(MOCVD)方法对横向外延(ELO)GaN薄膜的生长条件进行了研究.在蓝宝石衬底上利用化学腐蚀的方法刻饰出图案,再沉积低温GaN缓冲层作为外延层的子晶层,以降低外延层与衬底的晶格失配与热失配,制备出低位错密度的GaN外延层.分别利用X射线衍射、原子力显微镜及湿法腐蚀对外延层进行检测.     

MOCVD法侧向外延生长高质量GaN

利用金属有机物气相外延法(MOCVD),在GaN/蓝宝石复合衬底上,采用侧向外延生长技术制备出高质量的GaN外延膜,并对其进行扫描电镜、X射线双晶衍射、透射电镜测量和分析.发现完全合并后的GaN外延层的表面平整,晶体质量较衬底有大幅的提高,透射电镜进行微区位错观察发现窗口区穿透位错大部分发生转向,侧向生长区下方的穿透位错被掩膜阻断.     

蓝宝石衬底上侧向外延GaN中的位错降低

采用侧向外延(ELOG)方法,在制作了条形掩膜图形的GaN衬底上用MOCVD生长高质量GaN.AFM,化学湿法腐蚀及TEM分析表明:采用两步法ELOG生长的GaN中,掩膜下方的缺陷被掩膜所阻挡,窗口区内二次生长的GaN的位错也大幅降低;在相邻生长前沿所形成的合并界面处形成晶界;化学湿法腐蚀无法得到关于合并界面处缺陷的信息.侧翼区域中极低的穿透位错使得ELOG GaN适用于在其上制作高性能的氮化物基激光器.     

MOCVD法侧向外延生长高质量GaN

利用金属有机物气相外延法(MOCVD)，在GaN/蓝宝石复合衬底上，采用侧向外延生长技术制备出高质量的GaN外延膜，并对其进行扫描电镜、X射线双晶衍射、透射电镜测量和分析. 发现完全合并后的GaN外延层的表面平整，晶体质量较衬底有大幅的提高，透射电镜进行微区位错观察发现窗口区穿透位错大部分发生转向，侧向生长区下方的穿透位错被掩膜阻断.     

蓝宝石上横向外延GaN薄膜

在蓝宝石衬底上利用金属有机物气相外延(MOCVD)方法对横向外延(ELO)GaN薄膜的生长条件进行了研究.在蓝宝石衬底上利用化学腐蚀的方法刻饰出图案,再沉积低温GaN缓冲层作为外延层的子晶层,以降低外延层与衬底的晶格失配与热失配,制备出低位错密度的GaN外延层.分别利用X射线衍射、原子力显微镜及湿法腐蚀对外延层进行检测.     

Dislocation Reduction in GaN on Sapphire by Epitaxial Lateral Overgrowth

采用侧向外延(ELOG)方法,在制作了条形掩膜图形的GaN衬底上用MOCVD生长高质量GaN.AFM,化学湿法腐蚀及TEM分析表明:采用两步法ELOG生长的GaN中,掩膜下方的缺陷被掩膜所阻挡,窗口区内二次生长的GaN的位错也大幅降低;在相邻生长前沿所形成的合并界面处形成晶界;化学湿法腐蚀无法得到关于合并界面处缺陷的信息.侧翼区域中极低的穿透位错使得ELOG GaN适用于在其上制作高性能的氮化物基激光器.     

利用水平热壁CVD法生长的3C-SiC/Si的均匀性

利用新改进的水平低压热壁CVD设备,改变生长时的压力和H2流速,在50mm的Si(100)和(111)衬底上获得了3C-SiC外延膜,并对外延膜的结构均匀性、电学均匀性和厚度均匀性进行了分析.X射线衍射图中出现了强的3C-SiC的特征峰,其中3C-SiC的(200)和(111)峰的半高宽分别为0.41°和0.21°.3C-SiC外延膜方块电阻的均匀性最好可达2.15%.厚度均匀性可达±5.7%(σ/mean值).     

利用水平热壁CVD法生长的3C-SiC/Si的均匀性

利用新改进的水平低压热壁CVD设备,改变生长时的压力和H2流速,在50mm的Si(100)和(111)衬底上获得了3C-SiC外延膜,并对外延膜的结构均匀性、电学均匀性和厚度均匀性进行了分析.X射线衍射图中出现了强的3C-SiC的特征峰,其中3C-SiC的(200)和(111)峰的半高宽分别为0.41°和0.21°.3C-SiC外延膜方块电阻的均匀性最好可达2.15%.厚度均匀性可达±5.7%(σ/mean值).     

Characterization of GaN Buffer Layers and Its Epitaxial Layers Grown by MOCVD

Low-pressure MOCVD has been used to investigate the properties of low-temperature buffer layer depodition conditions and their influence on the properties of high-temperature GaN epilayers grown subsequently.It is found that the surface morphology of the as-grown buffer layer after thermal annealing at 1030℃and 1050℃ depends strongly on the thickness of the buffer layer.In particular when a thick buffer layer is used, large trapezoidal nuclei are formed after annealing.     

Photoelectric Properties of GaN Layers Grown by Plasma-Assisted Molecular-Beam Epitaxy on Si(111) Substrates and SiC/Si(111) Epitaxial Layers

Semiconductors - The photoelectric properties of GaN/SiC/Si(111) and GaN/Si(111) heterostructures grown by plasma-assisted molecular-beam epitaxy under the same growth conditions on identical...     

(111)A InP衬底上MOCVD外延InGaAsP的表面形貌和光学特性

为了研究(111)衬底的特性以及实现等边三角形微腔激光器,利用金属有机化学气相淀积(MOCVD)研究了(111)A InP衬底上InGaAsP外延层的表面形貌和光学特性。考虑到(111)A InP衬底的悬挂键密度比较低,在生长过程中有意提高了V／Ш比。通过扫描电子显微镜(SEM)和光荧光(PL)谱分别研究了外延层的表面形貌和光学特性。实验发现,表面形貌和光学特性随V／Ш比和温度的变化非常大。最佳V／Ш比和温度分别为400和625℃。     

Morphology of Thick SiC Epitaxial Films Grown by the Physical Vapor Transport Method

Epitaxial SiC films were deposited on on-axis Si-face 4H-SiC(0001) substrates by the physical vapor transport (PVT) method from a SiC powder. Scanning electron microscopy (SEM) showed a surface morphology which did not have any observable growth defects or cracking. We observed hexagonal growth morphology, a typical characteristic of diffusional growth. River patterns, free from microbubbles and microvoids, were observed on the as-grown surface. Morphology observed at 45° tilt in SEM revealed growth steps and coarsening of grains. An X-ray diffraction (XRD) rocking curve measured the full-width at half-maximum (FWHM) as 51.0 arc seconds and a reciprocal space map showed a singular intense region that is attributed to the high-quality homoepitaxial SiC film.     

Magnetic Properties of Thin Epitaxial SiC Layers Grown by the Atom-Substitution Method on Single-Crystal Silicon Surfaces

Semiconductors - A cycle of experimental investigations is carried out, specifically, the measurements and analysis of field dependences of the static magnetic susceptibility in samples of...     

Photoluminescence Characterization of Boron-doped Si Layers Grown by Molecular Beam Epitaxy

Photoluminescence spectra were used to characterize the boron-doped Si layers grown by molecular beam epitaxy using HBO2 as the doping source. The influence of boron doping concentration on the dislocation-related photoluminescence spectra of molecular beam epitaxy Si layers annealed at 900 ℃ was studied with different doping concentrations and growth temperature. The broad photoluminescence band（from 0.75 eV to 0. 90 eV） including D1 and D2 bands was associated with high boron doping concentration in the samples, while D3 and D4 bands might be related to oxygen precipitates.     

Electron-Microscopy Studies of the Structure of Thin Epitaxial Ge2Sb2Te5 Layers Grown on Si(111) Substrates

Semiconductors - For the creation of memory cells of new generation, structurally perfect epitaxial Ge2Sb2Te5 (GST) layers and multilayered crystalline structures based on GeTe/Sb2Te3 superlattices...     

Postgrowth Annealing of CdTe Layers Grown on Si Substrates by Metalorganic Vapor-Phase Epitaxy

Annealing conditions of CdTe layers grown on Si substrates by metalorganic vapor-phase epitaxy were studied. Typically, 3-μm-thick n-type (211) CdTe layers were annealed for 60 s in flowing hydrogen at atmospheric pressure by covering their surfaces with bulk CdTe wafers. At annealing temperatures above 700°C, improvement of crystal quality was confirmed from full-width at half-maximum values of double-crystal rocking-curve measurements and x-ray diffraction measurements. Photoluminescence measurements revealed no deterioration of electrical properties in the annealed n-CdTe layers. Furthermore, annealing at 900°C improved the performance of radiation detectors with structure of p-like CdTe/n-CdTe/n ⁺-Si substrate.