PVT法同质外延制备大尺寸Al极性氮化铝晶体生长工艺及其表征分析研究

本文基于自主设计的氮化铝生长炉,开展了四组不同工艺条件下Al极性面氮化铝籽晶同质外延生长氮化铝单晶的生长特征及其结晶质量表征研究。研究发现:不同工艺条件下生长的晶体的拉曼图谱E₂(high)特征峰峰位表明,晶体内部均存在较小的拉应力;在坩埚顶部在相对较高温度2 210 ℃、坩埚底部与顶部温差42 ℃的低过饱和度生长条件下,晶体表面光滑,呈现阶梯流生长形貌,并具有典型的氮化铝单晶生长习性面,晶体初始扩张角大于40°,高分辨率X射线衍射(HRXRD)测得0002、1012反射摇摆曲线及拉曼光谱检测结果表明,该条件下生长的氮化铝晶体结晶质量优异,并可实现快速扩径。基于该生长条件,通过外延生长后成功获得尺寸ϕ45~47 mm的氮化铝单晶锭,相关表征结果表明生长的氮化铝晶体具有优越的结晶性能。     

奥趋光电在氮化铝单晶生长领域取得突破性进展

<正>应诺贝尔物理奖获得者天野浩教授为会议主席的组委会邀请,奥趋光电技术(杭州)有限公司在日本横滨4月23～25日举行的LED工业应用国际会议(LEDIA-2019)上,推出了直径60 mm氮化铝单晶及晶圆,该晶圆为迄今为止国内外见诸报道的最大尺寸氮化铝晶圆。检测结果表明,晶片的拉曼半高宽仅为2. 85     

氮化铝晶体的生长惯习面和晶体形态

本文采用氧化铝碳热还原方法制备出了多种形态的氮化铝单晶(晶须).通过透射电子显微镜电子衍射和X射线单晶衍射分析,确定了氮化铝单晶常见的生长惯习面,并分析和讨论了氮化铝晶须形态与氮化铝晶体结构与生长惯习面的关系.具有规则六棱柱锥形的AlN晶须的生长取向为[0001]晶向,而叶片状和四方截面形状的AlN晶须则大多沿〈21-1-3-〉晶向进行生长,细小的薄片状AlN晶须则多以{101-0}面和{101-1}面为生长面.     

改进的升华法制备氮化铝单晶体

采用改进的升华法在氮气环境下制备氮化铝单晶体.通过优化实验条件制备出了六角形的高质量的氮化铝单晶体.实验发现,在坩埚的不同区域得到的氮化铝晶体的大小和形态有所不同.讨论了温度梯度对氮化铝晶体尺寸大小和形态的影响.     

PVT法AlN单晶生长技术研究进展及其面临挑战

氮化铝(AlN)具有超宽禁带宽度(6.2 eV)、高热导率(340 W/(m·℃))、高击穿场强(11.7 MV/cm)、良好的紫外透过率、高化学和热稳定性等优异性能,是氮化镓基(GaN)高温、高频、高功率电子器件以及高Al组分深紫外光电器件的理想衬底材料.物理气相传输(PVT)法是制备大尺寸高质量AlN单晶最有前途的方法.本文介绍了AlN单晶的晶体结构、基本性质及PVT法生长AlN晶体的原理与生长习性.基于AlN单晶PVT生长策略,综述了自发形核工艺、同质外延工艺及异质外延工艺的研究历程,各生长策略的优缺点及其最新进展.最后对PVT法生长AlN单晶的发展趋势及其面临的挑战进行了简要展望.     

三坩埚提拉法生长铽镓石榴石单晶研究

采用三坩埚提拉法生长出高质量铽镓石榴石(Tb3Ga5O12,TGG)单晶,晶体尺寸为φ25 mm×40 mm.通过X射线衍射、双晶衍射分析讨论TGG单晶的晶体结构和单晶性,并采用He-Ne激光费尔德常数测试装置测定TGG单晶的费尔德常数.结果表明:采用三坩埚提拉法生长的TGG单晶具有＜111＞取向、强度高,双晶摇摆曲线半峰宽为17 s;晶体在632.8 nm处的费尔德常数为0.553 min/cm·Oe.     

大尺寸单晶炉勾形磁场的优化设计

本文在分析cusp磁场抑制对流原理的基础上,采用有限元法对大尺寸单晶炉cusp磁场进行了建模.利用模型分析了磁场结构尺寸对磁场强度的影响,优化了磁场结构;分析了线圈规格对磁场功率的影响,优化了磁场功率;并通过实验验证了建模方法的有效性.实验结果表明:该模拟方法可用于大尺寸单晶炉cusp磁场的实际设计.     

奥趋光电实现2英寸氮化铝单晶衬底小批量量产

正奧趋光电技术(杭州)有限公司(以下简称"奥趋光电")日前发布了重磅产品——2英寸(Φ50.8 mm)高质量氮化铝单晶衬底,并正式启动小批量量产。随着2英寸氮化铝单晶衬底的小批量量产,高功率深紫外LED、紫外LD、紫外探测器、紫外预警及高功率、高频、高温电子器件等领域迎来了其最佳衬底材料及解决方案。     

提拉法制备铜单晶研究

采用提拉法生长出大尺寸(111)铜单晶,晶体尺寸为ф(12～19)mm×85 mm.通过XRD、金相显微分析讨论了铜单晶的晶体结构与生长缺陷,并采用双臂电桥测定(111)铜单晶的电阻率.结果表明:晶体具有(111)取向、强度高,表明晶体取向良好;蚀坑呈典型三角锥形,位错密度在105～106 cm-2之间;在室温下,(111)铜单晶电阻率为1.289×10-8Ω·m.     

大尺寸单晶金刚石制备的研究进展

单晶金刚石在电学,光学方面有着良好的应用前景,已经成为金刚石领域的研究焦点之一.本文论述了大尺寸单晶金刚石的制备方法、生长条件、研究现状以及存在的缺陷,概述了制备单晶金刚石过程中出现的问题并针对部分问题提出改善措施.     

坩埚预处理技术在氮化铝晶体生长工艺中的应用

在氮化铝晶体生长工艺中,坩埚的使用寿命是主要技术难点之一.实验发现,在钨坩埚体和盖之间放置内径和外径与坩埚相同的石墨环,在氮气环境下进行一次高温处理,使钨坩埚体与盖接触的部位形成碳化钨保护层,可以有效地解决高温下钨坩埚体与盖相粘结的问题,大大提高了坩埚的使用寿命.使用经过预处理的钨坩埚,用物理气相法生长出φ0.8mm×1.5mm氮化铝单晶体和φ36mm×5mm氮化铝多晶片.     

Numerical study of radial temperature distribution in the AlN sublimation growth system

A large radial temperature gradient in the AlN sublimation growth system would lead to non‐uniform growth rate along the radial direction and introduce thermal stress in the as grown crystal. In this paper, we have numerically studied the radial thermal uniformity in the crucible of a AlN sublimation growth system. The temperature difference on the source top surface is insignificant while the radial temperature gradient on the lid surface is too large to be neglected. The simulation results showed that the crucible material with a large thermal conductivity is beneficial to obtain a uniform temperature distribution on the lid surface. Moreover, it was found that the temperature gradient on the lid surface decreases with increased lid thickness and decreased top window size.     

Effect of the seed crystallographic orientation on AlN bulk crystal growth by PVT method

The growth of AlN crystals by PVT method was investigated using TaC crucible in the temperature range of 2250‐2350 °C. AlN boules with 30 mm in diameter were successfully grown on the crucible lid by self‐seeded growth. The AlN boules consist of the spontaneously nucleated AlN single crystal grains with the {1010} natural crystalline face. The fast growth rate of more than 1 mm/h was achieved. AlN crystals grown on (11 0)‐, (10 0)‐, and (0001)‐face AlN seeds were investigated. Different experimental phenomena have been observed under particular condition. The crystal grown on (11 0)‐face seed has different natural crystalline face from the seed. For the crystal grown on (10 0) or (0001) seed, the crystal natural crystalline face is same as the crystallographic orientation of the seed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

AlN bulk single crystal growth on 6H-SiC substrates by sublimation method

Large and thick AlN bulk single crystals up to 43 mm in diameter and 10 mm in thickness have been successfully grown on 6H-SiC (0 0 0 1) substrates by the sublimation method using a TaC crucible. Raman spectrum indicates that the polytype of the grown AlN single crystals is a Wurtzite-2H type structure, and the crystals do not include any impurity phases. The quality at the top of the crystal improves as crystal thickness increases along the 〈0 0 0 1〉 direction during growth: a low etch pit density (7×10⁴ cm⁻²) and a small full width at half maximum for a 0002 X-ray rocking curve (58 arcsec) have been achieved at a thickness of ∼8 mm. The possible mechanism behind the improvement in the AlN crystal quality is also discussed.     

PVT法SiC单晶生长传热分析

研究了PVT法生长SiC过程中的传热行为,以优化生长条件、获得高质量单晶.该研究是针对坩埚盖(籽晶粘附于坩埚盖上)和炉盖之间的传热行为进行的.研究认为,坩埚盖上部石墨毡开孔形状和大小对坩埚盖的径向温度场有很大影响.采用本文简化的模型可以估算坩埚在不同位置下、不同的石墨毡开孔形状和大小时坩埚盖和炉盖之间总的辐射热阻和传热量.对影响坩埚盖和炉盖之间传热的因素进行了讨论.另外,讨论了在生长过程中动态调整坩埚盖散热条件的可行性.     

Numerical simulation of a new SiC growth system by the dual-directional sublimation method

A new SiC growth system using the dual-directional sublimation method was investigated in this study. Induction heating and thermal conditions were computed and analyzed by using a global simulation model, and then the values of growth rate and shear stress in a growing crystal were calculated and compared with those in a conventional system. The results showed that the growth rate of SiC single crystals can be increased by twofold by using the dual-directional sublimation method with little increase in electrical power consumption and that thermal stresses can be reduced due to no constraint of the crucible lid and low temperature gradient in crystals.     

自发形核生长的AlN单晶湿法腐蚀研究

采用湿法腐蚀工艺,使用熔融态KOH和NaOH作为腐蚀剂,对一种物理气相传输(PVT)自发形核新工艺在2100~2250 ℃条件下生长的AlN单晶进行了腐蚀实验.通过实验及扫描电子显微镜(SEM)结果分析,得到了典型的AlN单晶c面、r系列面及m面最佳的腐蚀工艺参数及腐蚀形貌.另外,基于腐蚀形貌分析,发现了采用该自发形核新工艺生长的AlN晶体某些独特习性并计算出AlN单晶腐蚀坑密度(EPD).     

The impact of pressure and temperature on growth rate and layer uniformity in the sublimation growth of AlN crystals

To effectively design a large furnace for producing large-size AlN crystals, a fully coupled compressible flow solver was developed to study the sublimation and mass transport processes in AlN crystal growth. Compressible effect, buoyancy effects, flow coupling between aluminum gas and nitrogen gas, and Stefan effect are included. Two sets of experimental data were used to validate the present solver. Simulation results showed that the distributions of Al and N₂ partial pressures are opposite along the axial direction due to constant total pressure and Stefan effect, with the Al and nitrogen partial pressures being highest at the source and seed crystals positions, respectively. The distributions of species inside the growth chamber are obviously two-dimensional, which can curve a flat crystal surface. Simulation results also showed that AlN crystal growth rate can be increased by reducing total pressure or by increasing seed temperature or by increasing source-seed temperature difference. High nitrogen pressure causes decrease in growth rate, but it is beneficial for obtaining uniform growth rate in the radial direction. Results of simulation also showed that there is an optimized temperature difference (40 °C) in the present furnace for obtaining good homogeneity of growth rate.