Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

Hosung Seo,Marco Govoni,Giulia Galli

doi:10.1038/srep20803

Abstract

Spin defects in wide-band gap semiconductors are promising systems for the realization of quantum bits, or qubits, in solid-state environments. To date, defect qubits have only been realized in materials with strong covalent bonds. Here, we introduce a strain-driven scheme to rationally design defect spins in functional ionic crystals, which may operate as potential qubits. In particular, using a combination of state-of-the-art ab-initio calculations based on hybrid density functional and many-body perturbation theory, we predicted that the negatively charged nitrogen vacancy center in piezoelectric aluminum nitride exhibits spin-triplet ground states under realistic uni- and bi-axial strain conditions; such states may be harnessed for the realization of qubits. The strain-driven strategy adopted here can be readily extended to a wide range of point defects in other wide-band gap semiconductors, paving the way to controlling the spin properties of defects in ionic systems for potential spintronic technologies.

Highlights

PBE (a) and formation energy of VN and oxygen impurities (ON) computed within PBE0 (b)
We proposed a strain-driven defect design scheme to obtain point defects with localized spin-triplet ground states for implementation of spin qubits in piezoelectric aluminum nitride
We found that negatively charged nitrogen vacancies exhibit localized spin-triplet states in n-type aluminum nitride under realistic strain conditions

Summary

Introduction

The lowest-energy effective spin for a given charge state is shown. The inset of (b) is a schematic representation of the defect-molecule model of VN. The nearest neighbor Al atoms (numbered spheres) around the vacancy site and the Al sp[3] dangling bonds are shown for clarity. The Jahn-Teller distortions for the S = 0 and the S = 1 states are described by the e and a1+ e symmetrized displacements, respectively, as schematically shown next to the defect level diagrams. We found that by applying moderate uni- and bi-axial strain to the host lattice in the presence of negatively charged N vacancies, we could stabilize spin-triplet states, which are well-localized within the fundamental gap of n-type w-AlN.

Methods

Results

Conclusion