| AVS 65th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Tuesday Sessions |
| Session EM+2D+AN+MI+MP+NS-TuA |
| Session: | Solar/Energy Harvesting and Quantum Materials and Applications |
| Presenter: | Rachael Myers-Ward, U.S. Naval Research Laboratory |
| Authors: | R.L. Myers-Ward, U.S. Naval Research Laboratory K. Hobart, U.S. Naval Research Laboratory K.M. Daniels, U.S. Naval Research Laboratory A.J. Giles, U.S. Naval Research Laboratory M.J. Tadjer, U.S. Naval Research Laboratory L.E. Luna, U.S. Naval Research Laboratory F.J. Kub, U.S. Naval Research Laboratory S.P. Pavunny, U.S. Naval Research Laboratory S.G. Carter, U.S. Naval Research Laboratory H.B. Banks, U.S. Naval Research Laboratory E.R. Glaser, U.S. Naval Research Laboratory P.B. Klein, Sotera Defense Solutions K. Qiao, Massachusetts Institute of Technology Y. Kim, Massachusetts Institute of Technology J. Kim, Massachusetts Institute of Technology D.K. Gaskill, U.S. Naval Research Laboratory |
| Correspondent: | Click to Email |
Silicon carbide is a material of interest for quantum computing and sensing applications owing to deep point defect centers with long spin coherence times (which characterizes the lifetime of the qubit), specifically the VSi [1], divacancies [2] and nitrogen-vacancy centers [3]. These spin qubits have been isolated and coherently controlled, where VSi have T2 coherence times up to 100 µs [4] and divacancies to 1 ms [2], making these two defects of most interest to date. While the current spin coherence times have been shown to be as long as 1 ms, further improvements are needed to fully realize the potential of SiC for quantum applications. In this work, we create VSi in epitaxial SiC and investigate fabricating the layers into microstructures suitable for using the VSi photoluminescence (PL) emission. We have found 4H-SiC epitaxial layers grown under standard growth conditions and with varying doping densities from 1014 to 1018 cm-3 have no measureable VSi present, as determined by confocal PL. To introduce VSi, we used 2 MeV electron irradiation in doses ranging from 0.75 to 75 kGy. This results in VSi PL ranging from single to ensemble emission within the confocal volume. Hence, we are able to tune the vacancy concentration.
In order to improve the indistinguishable photons from the VSi and/or divacancies for real applications, photonic crystal cavities (PCC) are used to tune the emission energy [4]. Our PCC design consists of a planar array of cylindrical holes approximately 220 nm wide in a slab of SiC, ~300-500 nm thin having an area 50 x 50 µm2, similar to [4]. To maximize the PCC quality factor, the slab should have a large index of refraction difference on the top and bottom; i.e., an air gap is desired under the slab. To achieve this goal, we have identified four fabrication methods to create the PCC. One of these techniques is to use remote epitaxy as an innovative approach which entails growing epitaxial graphene on a SiC substrate by means of Si sublimation. Silicon carbide is then grown on a monolayer of graphene to the desired film thickness [5]. This thin SiC layer is then transferred, facilitated by the weak van der Waal forces at the graphene/SiC substrate interface, to a substrate more amenable to cavity fabrication. All four fabrication methods will be presented in detail.
[1] J.R. Weber, et al. Proc. Natl. Acad. Sci. USA 107 8513 (2010).
[2] D.J. Christle, et al., Nat. Mater. 14 160 (2015).
[3] H.J. von Bardeleben, J.L. Cantin, E. Rauls, and U. Gerstmann, Phys. Rev. B 92 064104 (2015).
[4] D.O. Bracher, X. Zhang and E.L. Hu, Proc, Natl. Acad. Sci. USA 114 4060 (2017).
[5] Y. Kim, et al., Nat. 544 340 (2017).