Modeling Formation and Stability of Fluorescent Defects in Wide-Bandgap Semiconductors

Abstract

Point defects in wide-bandgap semiconductors can be used to implement qubits that exploit spin-dependent fluorescence from electronic transitions. These qubits are the quantum mechanical analog of classical bits in that they leverage quantum mechanical properties such as superposition and entanglement and a spin-dependent fluorescence implies the ability to read out the qubit state optically. Fluorescent defects in wide-bandgap semiconductors such as diamond have long been studied, but an electronic spin coherence time exceeding one second at room temperature for the NV−, a defect in diamond comprised of a substitutional nitrogen atom adjacent to a carbon vacancy with a single negative charge, has only relatively recently been demonstrated. The demonstration of long-lived spin memory coupled with the fact that the NV− exhibits spin-dependent fluorescence spurred research on other point defects in diamond and in related materials such as silicon carbide for applications in quantum computing and quantum information as well as in magnetometry. However, maximizing the yield of point defects from the various techniques for creating them such as ion implantation or chemical vapor deposition is still not perfectly understood. Using density functional theory and kinetic Monte Carlo and molecular dynamics simulations, we provide an understanding of the thermodynamics and kinetics of point defect formation and migration that can be used to predict the annealing regimes that should lead to high yields and we provide a general framework that can be used to explain relative yields for various Fermi level regimes.