| 1. |
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| 2. |
- Anderson, Christopher P., et al.
(författare)
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Electrical and optical control of single spins integrated in scalable semiconductor devices
- 2019
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 366:6470, s. 1225-
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Tidskriftsartikel (refereegranskat)abstract
- Spin defects in silicon carbide have the advantage of exceptional electron spin coherence combined with a near-infrared spin-photon interface, all in a material amenable to modern semiconductor fabrication. Leveraging these advantages, we integrated highly coherent single neutral divacancy spins in commercially available p-i-n structures and fabricated diodes to modulate the local electrical environment of the defects. These devices enable deterministic charge-state control and broad Stark-shift tuning exceeding 850 gigahertz. We show that charge depletion results in a narrowing of the optical linewidths by more than 50-fold, approaching the lifetime limit. These results demonstrate a method for mitigating the ubiquitous problem of spectral diffusion in solid-state emitters by engineering the electrical environment while using classical semiconductor devices to control scalable, spin-based quantum systems.
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| 3. |
- Christle, David J., et al.
(författare)
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Isolated electron spins in silicon carbide with millisecond coherence times
- 2015
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 14:2, s. 160-163
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Tidskriftsartikel (refereegranskat)abstract
- The elimination of defects from SiC has facilitated its move to the forefront of the optoelectronics and power-electronics industries(1). Nonetheless, because certain SiC defects have electronic states with sharp optical and spin transitions, they are increasingly recognized as a platform for quantum information and nanoscale sensing(2-16). Here, we show that individual electron spins in high-purity monocrystalline 4H-SiC can be isolated and coherently controlled. Bound to neutral divacancy defects(2,3), these states exhibit exceptionally long ensemble Hahn-echo spin coherence times, exceeding 1 ms. Coherent control of single spins in a material amenable to advanced growth and microfabrication techniques is an exciting route towards wafer-scale quantum technologies.
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| 4. |
- Christle, David J., et al.
(författare)
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Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface
- 2017
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Ingår i: Physical Review X. - : AMER PHYSICAL SOC. - 2160-3308. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- The divacancies in SiC are a family of paramagnetic defects that show promise for quantum communication technologies due to their long-lived electron spin coherence and their optical addressability at near-telecom wavelengths. Nonetheless, a high-fidelity spin-photon interface, which is a crucial prerequisite for such technologies, has not yet been demonstrated. Here, we demonstrate that such an interface exists in isolated divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that divacancies in 4H-SiC have minimal undesirable spin mixing, and that the optical linewidths in our current sample are already similar to those of recent remote entanglement demonstrations in other systems. Moreover, we find that 3C-SiC divacancies have a millisecond Hahn-echo spin coherence time, which is among the longest measured in a naturally isotopic solid. The presence of defects with these properties in a commercial semiconductor that can be heteroepitaxially grown as a thin film on Si shows promise for future quantum networks based on SiC defects.
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| 5. |
- Davidsson, Joel, et al.
(författare)
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Identification of divacancy and silicon vacancy qubits in 6H-SiC
- 2019
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 114:11
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Tidskriftsartikel (refereegranskat)abstract
- Point defects in semiconductors are relevant for use in quantum technologies as room temperature qubits and single photon emitters. Among suggested defects for these applications are the negatively charged silicon vacancy and the neutral divacancy in SiC. The possible nonequivalent configurations of these defects have been identified in 4H-SiC, but for 6H-SiC, the work is still in progress. In this paper, we identify the different configurations of the silicon vacancy and the divacancy defects to each of the V1-V3 and the QL1-QL6 color centers in 6H-SiC, respectively. We accomplish this by comparing the results from ab initio calculations with experimental measurements for the zero-phonon line, hyperfine tensor, and zero-field splitting. Published under license by AIP Publishing.
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| 6. |
- de las Casas, Charles F., et al.
(författare)
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Stark tuning and electrical charge state control of single divacancies in silicon carbide
- 2017
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Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 111:26
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Tidskriftsartikel (refereegranskat)abstract
- Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color centers whose long coherence times and near-telecom operating wavelengths make them promising for scalable quantum communication technologies compatible with existing fiber optic networks. However, local strain inhomogeneity can randomly perturb their optical transition frequencies, which degrades the indistinguishability of photons emitted from separate defects and hinders their coupling to optical cavities. Here, we show that electric fields can be used to tune the optical transition frequencies of single neutral divacancy defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same technique can also control the charge state of the defect on microsecond timescales, which we use to stabilize unstable or non-neutral divacancies into their neutral charge state. Using fluorescence-based charge state detection, we show that both 975 nm and 1130 nm excitation can prepare their neutral charge state with near unity efficiency. (C) 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons. org/licenses/by/4.0/).
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| 7. |
- Duc Tran, Thien, et al.
(författare)
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Deep levels in as-grown and electron-irradiated n-type GaN studied by deep level transient spectroscopy and minority carrier transient spectroscopy
- 2016
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 119:9
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Tidskriftsartikel (refereegranskat)abstract
- By minority carrier transient spectroscopy on as-grown n-type bulk GaN produced by halide vapor phase epitaxy (HVPE) one hole trap labelled H1 (EV + 0.34 eV) has been detected. After 2 MeV-energy electron irradiation, the concentration of H1 increases and at fluences higher than 5×1014 cm-2, a second hole trap labelled H2 is observed. Simultaneously, the concentration of two electron traps, labelled T1 (EC - 0.12 eV) and T2 (EC - 0.23 eV) increases. By studying the increase of the concentration versus electron irradiation fluences, the introduction rate of T1 and T2 using 2 MeV-energy electrons was determined to 7X10-3 cm-1 and 0.9 cm-1, respectively. Due to the low introduction rate of T1 and the low threading dislocation density in the HVPE bulk GaN material, it is suggested that the defect is associated with a primary defect decorating extended structural defects. The high introduction rate of the trap H1 suggests that the H1 defect is associated with a primary intrinsic defect or a complex.
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| 8. |
- Duc Tran, Thien, et al.
(författare)
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Electronic properties of defects in high-fluence electron irradiated bulk GaN
- 2016
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Ingår i: Physica status solidi. B, Basic research. - : John Wiley & Sons. - 0370-1972 .- 1521-3951. ; 253:3, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- Using deep level transient spectroscopy, deep levels and capture cross sections of defects introduced by high-fluence electron irradiation of thick halide vapour phase epitaxy grown GaN has been studied. After irradiation with 2 MeV electrons to a high-fluence of 5×1016 cm-2, four deep trap levels, labelled T1 (EC – 0.13 eV), T2 (EC – 0.18 eV), T3 (EC – 0.26 eV) T4 and a broad band of peaks consisting of at least two levels could be observed. These defects, except T1 and T3, were annealed out after annealing at 650 K for 2 hours. The capture cross section is found to be temperature independent for T2 and T3, while T1 shows an decresing capture cross section with increasing temperature, suggesting that electron capturing to this deep level is governed by a cascade capturing process.
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| 9. |
- Duc Tran, Thien, et al.
(författare)
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Thermal behavior of irradiation-induced-deep levels in bulk GaN
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bulk GaN grown by halide vapor phase epitaxy and irradiated by 2 MeV electrons at a fluence of 5×1016 cm-2 were studied by deep level transient spectroscopy. After irradiation, two new peaks labelled D0 (EC – 0.18 eV) and D1 (EC – 0.13 eV) are observed. From isochronal annealing studies in the temperature range of 350 - 600 K, it is observed that peak D0 is completely annealed out already at 550 K while the broad peak D1 has a more complex annealing behavior. The concentration of D1 is decreasing during annealing and its peak position is shifted to higher temperatures, until a relatively stable peak labelled D2 (EC – 0.24 eV) is formed. From an isothermal annealing study of D2, it is concluded that the annealing process can be described by a first order annealing process with an activation energy and prefactor of 1.2 eV and 6.6 × 105 s-1, respectively. From the large pre-factor it is concluded that the annihilation of D2 is governed by a long-range migration process. From its annealing behavior, it is suggested that trap D2 may be related to the VGa.
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| 10. |
- Ivády, Viktor, et al.
(författare)
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Identification of Si-vacancy related room-temperature qubits in 4H silicon carbide
- 2017
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 96:16
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Tidskriftsartikel (refereegranskat)abstract
- The identification of a microscopic configuration of point defects acting as quantum bits is a key step in the advance of quantum information processing and sensing. Among the numerous candidates, silicon-vacancy related centers in silicon carbide (SiC) have shown remarkable properties owing to their particular spin-3/2 ground and excited states. Although, these centers were observed decades ago, two competing models, the isolated negatively charged silicon vacancy and the complex of negatively charged silicon vacancy and neutral carbon vacancy [Phys. Rev. Lett. 115, 247602 (2015)], are still argued as an origin. By means of high-precision first-principles calculations and high-resolution electron spin resonance measurements, we here unambiguously identify the Si-vacancy related qubits in hexagonal SiC as isolated negatively charged silicon vacancies. Moreover, we identify the Si-vacancy qubit configurations that provide room-temperature optical readout.
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