Defects in SiC for Quantum Computing
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.301
Defects in SiC for Quantum Computing Renu Choudhary,1 Rana Biswas,1,2 Bicai Pan,3 Durga Paudyal1 1
Ames Laboratory, Iowa State University, Ames IA, USA 50011
2
Departments of Physics and Astronomy, Electrical and Computer Engineering, and Microelectronics Research Center, Iowa State University, Ames, Iowa 50011, USA
3
Department of Physics, University of Science and Technology of China, Hefei, China.
Abstract Many novel materials are being actively considered for quantum information science and for realizing high-performance qubit operation at room temperature. It is known that deep defects in wide-band gap semiconductors can have spin states and long coherence times suitable for qubit operation. We theoretically investigate from ab-initio density functional theory (DFT) that the defect states in the hexagonal silicon carbide (4H-SiC) are potential qubit materials. The DFT supercell calculations were performed with the local-orbital and pseudopotential methods including hybrid exchange-correlation functionals. Di-vacancies in SiC supercells yielded defect levels in the gap consisting of closely spaced doublet just above the valence band edge, and higher levels in the band gap. The divacancy with a spin state of 1 is charge neutral. The divacancy is characterized by C-dangling bonds and a Si-dangling bonds. Jahnteller distortions and formation energies as a function of the Fermi level and single photon interactions with these defect levels will be discussed. In contrast, the anti-site defects where C, Si are interchanged have high formation energies of 5.4 eV and have just a single shallow defect level close to the valence band edge, with no spin. We will compare results including the defect levels from both the electronic structure approaches.
INTRODUCTION The field of quantum information science has been rapidly expanding exploring new materials suitable for realizing quantum bits (qubits). [1] Qubits are the basic construct of quantum information and consist of a spin in a solid that is largely decoupled from its environment. The qubit is an intrinsically quantum object, that can be utilized to store and process information. [1] Many materials have been considered for realizing qubits. Wide band gap semiconductors are particularly attractive for qubits [1,2,3], since
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they are well known to have point defects, that have deep defect levels within the band gap. Many of this point defects can have high spin states depending on the position of the Fermi level. Moreover, since these defect levels are separated in energy from the band edges in wide band gap semiconductors, the electronic states of these defects are well localized and are not appreciably extended into the host semiconductor. Such isolate
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