High-Field EPR/ENDOR of N/Be Centers for Defect Engineering in 6H-SiC

Research Overview

Silicon carbide (SiC) is a leading candidate for quantum technologies due to its wide bandgap and the ability to host stable, addressable spin defects. While nitrogen is a well-characterized donor in SiC, beryllium acts as an acceptor, offering a pathway to create p-n junctions and complex electronic structures. This study investigates the microscopic spin properties of nitrogen and beryllium co-doped 6H-SiC to understand how these impurities interact with the crystal lattice and each other.

Experimental Approach

The researchers utilized a combination of continuous-wave and pulsed electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. By performing measurements in the W-band (94 GHz, 3.4 T), the team achieved significantly higher spectral resolution than standard X-band experiments. This high-field approach was critical for separating overlapping signals from different lattice sites and resolving the hyperfine structures associated with the 9Be isotope (nuclear spin I = 3/2).

Key Findings

The high-field EPR data allowed the researchers to distinguish between nitrogen donors and beryllium acceptors in various crystallographic environments. Specifically, the study identified that beryllium occupies both hexagonal (h) and quasi-cubic (k1, k2) sites. The hexagonal site exhibits a stable, axial configuration, while the quasi-cubic sites show evidence of a dynamic Jahn-Teller effect, where rapid hopping between local energy minima partially averages the electronic wave function. Furthermore, the team measured phase coherence (T2) and spin-lattice relaxation (T1) times, finding that nitrogen and beryllium centers exhibit distinct relaxation signatures. These results confirm that dual-impurity doping is feasible in 6H-SiC without compromising the structural integrity of the crystal, providing a foundation for integrating quantum spin centers with conventional semiconductor electronics.

Understanding the local environment and spin dynamics of dopants is essential for designing scalable quantum devices. By mapping the spin density and identifying the specific lattice configurations of nitrogen and beryllium, this work provides the necessary parameters to optimize coherence times and control spin states in SiC-based quantum platforms.