Development of Diamond-Based Materials Systems for High-Power RF Electronics: Fourth-Year Report

Author(s):

Pulickel M. Ajayan, Robert Vajtai, Xiang Zhang, Anand B. Puthirath, Abhijit Biswas, Eliezer Oliveira, Chenxi Li, Harikishan Kannan, Tia Gray, Jacob Elkins, Tim Pieshkov, Jishnu Murukeshan, Tony Ivanov, Nicholas R. Jankowski, A. Glen Birdwell, Mahesh Neupane, Bradford B. Pate, Elias Garratt, Sergey Rudin, Dmitry Ruzmetov, Pankaj Shah, James Weil, Leonard De La Cruz, Derwin Washington, Stephen B. Kelley, and Brittany Kaufmann

Abstract:

This report details the fourth-year research effort that is part of the cooperative agreement between Rice University and the DEVCOM Army Research Laboratory (ARL). The project aims to develop diamond and diamond-based heterostructures for the next-generation of ultra-wide bandgap electronic devices, with performances far exceeding those of wide bandgap materials-based devices. The Rice University team is primarily focused on cultivating high-quality single-crystal diamond (SCD) substrates and heterostructures, involving diamond and boron nitride (BN). Simultaneously, ARL is constructing high-performance electronic devices based on diamond. Rice has established a world-class facility dedicated to growing SCDs and heterostructures. The work in the first, second, and third years encompassed activities such as BN growth and transfer on commercially available diamond substrates, ion implantation for doping, BN structure deposition on diamond, development of unique metrology tools for characterizing diamond surfaces and heterostructures, surface modification through hydrogenation and oxygenation, theoretical modeling to comprehend growth, and surface characteristics of diamond and diamond/BN heterostructures. In the fourth year, attempts were made to grow single-crystal diamond wafers, and growth protocols were optimized for various thicknesses of epilayers and growth rates on desired substrates. For BN nitride growth, there is an ongoing exploration of the phase diagram for different BN phases (hexagonal, cubic, turbo-static, wurtzite). Improvements in metrology aspects, enhancing resolution in microscopy and spectroscopy and THz spectroscopy for grown single-crystal structures and epitaxially grown heterostructures, are optimized. Surface functionalization approaches are being employed to enhance the functionalities of diamond surfaces, and these are being comprehended through theoretical and computational modeling. Also, reactive ion etching is being employed for clean and low-roughness diamond wafers. Additionally, experiments involving low-energy ion implantation are being conducted to n-dope diamond wafers and produce color centers. The synergy between the two institutions fosters a close working relationship, leading to the synthesis of controlled diamond materials and their use in high-power devices.