Single Photon Emission from Vanadium Defects in Silicon Carbide
Brandon Demory | 21-FS-001
Reliable qubit generation is one of the biggest focus areas in quantum computing, sensing, and communications. An ideal single photon source (SPS) is a prime candidate for qubit generation as it can generate on-demand, indistinguishable photons with high brightness and fidelity. Vanadium in crystalline silicon carbide (SiC) has been studied extensively and demonstrates the properties of an ideal SPS emitting in the telecom band near 1300nm, with the potential for room temperature operation. However, crystalline SiC suffers from integration challenges with conventional silicon photonics, which limits the coupling efficiency and brightness of the sources, lowering its overall effectiveness as a SPS host material. To address these challenges, we chose a new host material for the Vanadium (V) ion emitter: amorphous silicon carbide (a-SiC), that is a great host material because it is scalable, compatible with silicon CMOS processing, builds upon existing SiC processes, and possesses excellent substrate compatibility due to its amorphous nature. In this work, we explored the feasibility of a-SiC as a Vanadium ion host to generate single photons and how this compares to the well-studied crystalline counterpart.
The Vanadium doped a-SiC study involved material growth and ion implantation optimization, via modeling of Vanadium incorporation into the a-SiC, and photoluminescence optical characterization, to build up the Vanadium SPS system. First, we optimized the a-SiC deposition parameters, to retain the favorable optical properties of crystalline SiC, (refractive index, density, bandgap, and transparency), while leveraging the lower growth temperature of the amorphous film. Next, V ion implantation was simulated to verify ion implantation conditions. To spatially separate the emitters, lower V ion density was achieved using a metal masking method. After material implantation was successfully completed, zero phonon line (ZPL) emission from the V ion was demonstrated at the cryogenic temperature of 24 Kelvin using photoluminescence spectroscopy, nearly identical to the ZPL emission of 4H polytype crystalline SiC with V incorporated during growth. Modeling of V defects in a-SiC illustrate that Vanadium incorporates into the vacancies of the amorphous film and thus emits, while, by comparison, V implanted silicon dioxide and silicon nitride samples did not present V ZPL emission, further corroborating our results. These results are significant as this is the first demonstration to our knowledge in literature of this emitter and host combination. This result serves as the building block for future integrated SPSs in SiC.
The purpose of this work is to develop the quantum source material in a-SiC, which will act as the foundation for future photonic integrated quantum devices. Current methods of single photon and qubit generation have pitfalls that limit their ability for integration, high fidelity, and security. The SiC source has the ideal properties to surpass the current state of the art of single photon generation in those categories. Development of this a-SiC source leverages compatibility with silicon photonics while enabling new communication capability, sensing capability, and foundations for future quantum computing architecture, which expands the toolset and capabilities necessary to meet future national security challenges. This work has expanded the collaboration of Lawrence Livermore National Laboratory with University of California Berkeley and local semiconductor companies. There is an abundance of external funding associated with quantum sources since many organizations, including Argonne National Laboratory, are looking for the best solution to the problem of qubit generation and entanglement for highly sought quantum repeaters and interconnects.
Publications, Presentations, and Patents
Based on the initial results, a Record of Invention has been filed for this work (IL-13711).