Growth of Gallium Nitride and Related Materials at Subatmospheric Pressures

该项目介绍了从熔体中结晶III族氮化物的新方法。活动包括：块状多晶和单晶氮化镓和氮化铟的生长；在衬底上合成厚膜和薄膜GaN和InN；以及晶体的光学、电子和结构表征。其目的是为目前合成块状III族氮化物的高压工艺提供一个有吸引力的替代方法；增加对III族氮化物/氮系统中的相关系的了解；并进一步深入了解合金化、杂质、缺陷和晶界对III族氮化物发光的作用。方法是使用原子氮来产生饱和的镓(或铟)熔体，从中可以结晶出GaN(或InN)。在低压下，如果GaN和InN晶体与氮饱和熔体接触，则GaN和InN分解为元素的过程受到抑制。研究的重点将是通过控制温度和浓度梯度来实现单晶和单晶膜的稳定生长。水平梯度冻结和通过液体薄膜生长(一种形式的液体外延)将是主要的方法。第三种元素，如In和Sn，将被用来降低液相线温度并提高氮的溶解度。将尝试通过在原始液态金属中加入少量受控掺杂剂来进行掺杂研究，例如，镁和硅。综合工作将得到同时进行的电学、光学和结构表征的补充。%该项目解决具有高潜在技术相关性的材料科学主题领域的基础研究问题。这项研究将在基础水平上为电子/光子器件的重要制造方面贡献基础材料科学知识。现在有了新的实验材料科学和光学工具，以实现新的方法，这些方法如果得到更好的理解，就会促进基础科学和技术的进步。从研究中获得的基本知识和理解有望有助于提高用于计算和通信的先进器件和电路的性能。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。

This project addresses new methods for crystallization of the group III nitrides from the melt. Activities include: growth of bulk polycrystalline and single crystal gallium nitride and indium nitride; synthesis of thick and thin film GaN and InN on substrates; and optical, electronic, and structural characterization of the crystals. The aim is to provide an attractive alternative to the current high pressure process for synthesis of bulk group III nitrides; increased understanding of the phase relationships in the group III/nitrogen systems; and further insights into the role of alloying, impurities, defects, and grain boundaries on light emission from the group III nitrides. The approach is to use atomic nitrogen to produce saturated melts of gallium (or indium) from which GaN (or InN) can be crystallized. The decomposition of GaN and InN to the elements is suppressed at low pressures if the crystals are in contact with the nitrogen saturated melt. A main focus of the research will be to achieve stable growth of single crystals and single crystal films through control of temperature and concentration gradients. Horizontal gradient freezing and growth through thin liquid films (a form of liquid phase epitaxy) will be the principal methods employed. Third elements, e.g., In and Sn, will be used to suppress the liquidus temperature and enhance nitrogen solubility. Doping studies will be attempted by including small, controlled amounts of dopants, e.g., Mg and Si, in the original liquid metal. The synthetic work will be complemented by concurrent electrical, optical and structural characterization.%%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important fabrication aspects of electronic/photonic devices. New experimental materials science and optical tools are now available to allow new approaches which when better understood provide advances in fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the perform-ance of advanced devices and circuits for computing and communications. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area.***