Controlling AlInGaN/Silicon Interface Kinetics

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Nontechnical Description: The focus of this project is to develop an increased understanding of the synthesis of nitride-based materials on silicon, combining the two most widely available semiconductors - Silicon and Nitrides. In spite of their importance in a variety of devices such as light-emitting diodes (LEDs), power transistors, and high-efficiency solar cells, much remains unknown about the crystalline growth processes occurring at the interface between these important materials. In order to achieve the integration of these materials for next generation devices, an improved understanding of the interface chemistry, growth mechanisms, metallurgical reactions, and resulting defect formation at this important interface is needed. This project utilizes a recently developed low temperature crystal growth process, capable of achieving commercially advantageous, high-throughput rates with various analyses to study the complex interfacial phenomena and extend the use of III-Nitrides to include the elusive material AlGaInN. A mechanism to control these phenomena, possibly reducing defects and enabling future applications is also targeted. This project provides graduate students access to cutting-edge technology and resources at the intersection of physics, materials science, and nanoelectronics. The resulting device platform has the potential to lead to innovations in energy saving devices, communications, solar cells, and medical device technologies. Social and academic outreach programs are expanded to include demonstrations for elementary to high school students. This research provides new opportunities for the dissemination and publication of detailed methods for achieving (AlGaIn)-Nitride and Silicon device integration. Technical Description: This project explores the development of heterostructures composed of quaternary III-Nitrides (AlGaInN) and Silicon for electronic and optoelectronic device integration. While AlN on Silicon is largely commercialized, all other commonly available III-Nitride alloys including GaN, InN, AlGaN and InGaN are substantially not implemented directly on Silicon substrates. Furthermore, the daunting challenge of growing quaternaries of AlGaInN has not been mastered, especially not on silicon substrates. Early attempts to control the naturally occurring growth phenomena at III-Nitride/Si interfaces were limited to the case where an insulating aluminum nitride interlayer was acceptable, as in lateral transistors like high-electron mobility transistors (HEMTs). For those cases where insulating barriers are not acceptable, as in future vertical conduction devices, e.g. transistors, LEDs, solar cells, and power devices, limited scientific understanding and no existing commercial success has been demonstrated. The recent demonstration of low temperature, rapid growth methods such as Metal Modulated Epitaxy (MME) with growth rates up to 9.8 microns/hr is providing new possibilities to "freeze in" new phases thought previously too challenging. Since MME is performed at extremely low temperatures (300 degrees C for indium nitride and ~500-600 degrees C for gallium nitride), the ability to control the interface diffusion, elimination of eutectic driven substrate etching, and control of interface planarity, all by using kinetically limited diffusion is viable. Furthermore, having already been proven to overcome phase separation challenges of InGaN, MME is viable for overcoming the same challenges of quaternary AlGaInN as well. The goal of this basic research effort is to better understand and control the interface kinetics of III-Nitride/Silicon heterojunctions, provide high quality quaternary III-Nitride materials and identify a better solution for vertical conduction devices integrated on silicon that eliminates the insulating AlN interlayer commonly used in silicon/nitride electronics today. The successful execution of this project has the potential to lead to a detailed understanding of the chemical and metallurgical interactions between III-Nitrides and Silicon including quantification of diffusion and reaction coefficients. This is the foundation required for next generation vertical power transistors on silicon that integrate smart CMOS devices with the enhanced power handling capabilities of III-Nitrides and LEDs for solid-state lighting grown on low-cost (even removable/disposable) large area silicon substrates.