Oxide and Nitride Films for Tunable Capacitors and HEMTs

Overview

The document is the final report for ONR Grant N00014-05-1-0238, titled "Multifunctional Oxide Films for Advanced Multifunction RF Systems," compiled by Dr. Volker D. Heydemann from the Penn State Electro-Optics Center. The reporting period spans from February 15, 2005, to March 31, 2007, and it addresses the challenges faced by the U.S. Navy in adapting to new technological demands for information superiority and situational awareness.

The report outlines the transition from separate RF systems for radar, communication, and electronic warfare to integrated multifunction RF systems. This integration aims to overcome limitations such as tracking stealth targets and ensuring interoperability among platforms. The development of new materials and device technologies is essential for the next generation of these systems, particularly for high-power amplifiers operating at or beyond X-band frequencies.

A significant focus of the research is on the development of tunable capacitors with a wide tunability range and high power operation capabilities. The report discusses the exploration of high-k dielectric materials, such as barium-strontium titanate (Ba-xSrxTiO3) and strontium titanate (SrTiO3), which are promising for enhancing the performance of passive components in RF systems.

The document also details the establishment of a custom molecular beam epitaxy (MBE) system designed for the growth of oxide and nitride thin films. This system includes a multi-beam optical stress sensor (MOSS) for monitoring substrate stress and curvature during the growth process. The report emphasizes the importance of achieving atomically flat substrate surfaces for successful MBE epitaxy, which is facilitated by a hydrogen etching system developed for this purpose.

Additionally, the report addresses the need to control and customize the interfaces between silicon carbide (SiC) or III-nitride and oxide films to minimize defect generation and leakage currents, which are critical for optimizing varactor performance.

In summary, the report presents a comprehensive overview of the research conducted on multifunctional oxide films, highlighting the innovative approaches taken to meet the evolving needs of RF systems in military applications. The findings contribute to the advancement of materials and technologies necessary for the development of integrated multifunction RF systems.