Development of Diamond-Based Materials Systems for High-Power RF Electronics: Third-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, Tony Ivanov, Nicholas R Jankowski, A Glen Birdwell, Bradford B Pate, Mahesh Neupane, 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 third-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 ultrawide bandgap electronic devices, with performances far exceeding existing diamond devices and other wide bandgap materials-based devices. The Rice team focuses on the growth of high-quality single crystal diamond substrates and heterostructures of diamond and boron nitride (BN), and ARL is building high-performance electronic devices based on diamond, specifically using transfer doping of hydrogenated diamond surfaces. Rice has established a world-class facility to grow single crystal diamonds and heterostructures. First- and second-year work have included growth and transfer of BN on commercially available diamond substrates; doping using ion implantation; deposition of BN structures on the diamond; development of unique metrology tools to characterize diamond surfaces, heterostructures, and devices; surface modification using hydrogenation and oxygenation; and theoretical models to understand growth, adhesion energy, and surface characteristics of diamond and diamond/BN heterostructures. During the third year, polycrystalline and single crystalline diamond wafer growth are attempted in-house, and optimized growth protocols for varied thicknesses of epilayers and growth rates at desired substrates. When it comes to BN growth, exploration of the phase diagram for different phases of BN (hexagonal, cubic, turbo-static, wurtzite) is being attempted. Metrology is improving for the resolution in microscopy and spectroscopy aspects of the grown single crystal structures and epitaxially grown heterostructures. Surface functionalization approaches are being performed to improve the functionalities of diamond surfaces and are being understood by theoretical and computational modeling. In addition, low-energy ion implantation experiments are being performed to n-dope diamond wafers. The synergy between the two institutions establishes a close working relationship, leading to the synthesis of controlled diamond materials and their use in high-power devices.