GOALI: Strained Layer Heterostructures for GaN-on-Si Epitaxy

非技术描述：氮化镓是一种重要的半导体，因为它在固态照明和电力电子中有广泛的应用。宾夕法尼亚州立大学和高效电力转换(EPC)公司在这个目标项目中合作，开发材料生长技术，将氮化镓薄膜与用于集成电路制造的标准衬底硅片集成在一起。直接结合这两种材料的能力将允许针对各种应用的电路设计的灵活性。然而，氮化镓的六方晶体结构与(100)硅的立方晶体结构不相容。这个项目试图通过故意在硅中引入应变来改变硅的表面结构，从而减少晶体失配，从而克服这些限制。晶片曲率的实时测量被用来直接测量硅衬底中的应变，并研究氮化镓沉积过程中薄膜应力的动态变化。生长后结构表征被用来解释应力产生和松弛的机制。该项目支持宾夕法尼亚州立大学两名研究生的博士论文工作，他们通过与EPC的合作，接触到与全球半导体代工厂的工艺扩大和制造相关的问题。来自宾夕法尼亚州代表性不足群体和经济困难地区的本科生和高中生通过宾夕法尼亚州州立大学的暑期项目参与了这项研究。技术描述：该项目是关于在轴向(100)硅衬底上外延生长用于混合电力电子电路的AlGaN/GaN异质结。应变Si/SiGe虚拟衬底被认为是控制(100)Si表面的主导重构，从而减少AlN核的面内旋转错位的一种途径。利用原位晶片曲率测量来监测SiGe层中的应力松弛，测量生长温度下硅层中的拉伸应变，并研究其对GaN/AlN异质外延的影响。还研究了n型掺杂化学对GaN应力演化的影响。该项目试图从根本上理解硅表面应变在GaN/AlN外延中的作用，从而可以用来在功率器件的(100)Si上发展AlGaN/GaN二维电子气异质结。该项目团队在第三类氮化物异质外延硅衬底(宾夕法尼亚州立大学)和功率场效应管(EPC)用硅上氮化镓(GaN-on-Si)的工艺放大和商业化方面拥有互补的专业知识。此外，EPC处于有利地位，可以利用本项目中开发的GaN on(100)Si生长技术实现的混合电路设计。

Non-technical Description: Gallium nitride is an important semiconductor due to its wide ranging applications in solid-state lighting and power electronics. Pennsylvania State University and Efficient Power Conversion (EPC) Corporation are partnering in this GOALI project to develop materials growth technology to integrate gallium nitride thin films with silicon wafers, which are the standard substrates used for integrated circuit fabrication. The ability to directly combine these two materials would allow flexibility in circuit design for a variety of applications. However, the hexagonal crystal structure of gallium nitride is incompatible with the cubic crystal structure of (100) silicon. This project seeks to overcome these limitations by intentionally introducing strain into the silicon to alter the surface structure and thereby reduce the crystal mismatch. Real-time wafer curvature measurements are used to directly measure strain in the silicon substrate and study dynamic changes in film stress during gallium nitride deposition. Post-growth structural characterization is used to elucidate mechanisms of stress generation and relaxation. The project supports the Ph.D. thesis work of two graduate students at Penn State University who are exposed to issues relevant to process scale-up and manufacturing in a global semiconductor foundry through the collaboration with EPC. Undergraduates and high-school students from underrepresented groups and economically challenged regions of Pennsylvania are participating in the research through summer programs at Penn State University. Technical Description: This GOALI project is on the epitaxial growth of AlGaN/GaN heterostructures on on-axis (100) Si substrates for hybrid power electronics circuits. Strained Si/SiGe virtual substrates are being explored as a route to control the dominant reconstruction of the (100) Si surface and thereby reduce the in-plane rotational misalignment of AlN nuclei. In-situ wafer curvature measurements are used to monitor stress relaxation in the SiGe layers and measure tensile strain in the Si layer at the growth temperature and study its impact on GaN/AlN heteroepitaxy. The effects of n-type dopant chemistry on stress evolution in GaN are also being examined. The project seeks a fundamental understanding of the role of Si surface strain on GaN/AlN epitaxy, which can then be exploited to develop AlGaN/GaN two-dimensional electron gas heterostructures on (100) Si for power devices. The project team has complementary expertise in group III-nitride heteroepitaxy on Si substrates (Penn State University) and process scale-up and commercialization of GaN-on-Si for power field-effect transistors (EPC). In addition, EPC is well positioned to capitalize on hybrid circuit designs that will be enabled by the GaN on (100) Si growth technology developed in this project.