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1. Electric field induced migration of native point defects in Ga2O3 devices

   https://doi.org/10.1063/5.0124543  

   Haseman, Micah S.; Ramdin, Daram N.; Li, Wenshen; Nomoto, Kazuki; Jena, Debdeep; Xing, Huili Grace; Brillson, Leonard J. (January 2023, Journal of Applied Physics)

   While the properties of β-Ga2O3 continue to be extensively studied for high-power applications, the effects of strong electric fields on the Ga2O3 microstructure and, in particular, the impact of electrically active native point defects have been relatively unexplored. We used cathodoluminescence point spectra and hyperspectral imaging to explore possible nanoscale movements of electrically charged defects in Ga2O3 vertical trench power diodes and observed the spatial rearrangement of optically active defects under strong reverse bias. These observations suggest an unequal migration of donor-related defects in β-Ga2O3 due to the applied electric field. The atomic rearrangement and possible local doping changes under extreme electric fields in β-Ga2O3 demonstrate the potential impact of nanoscale device geometry in other high-power semiconductor devices. 

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2. Electrical and optical control of single spins integrated in scalable semiconductor devices

   https://doi.org/10.1126/science.aax9406  

   Anderson, Christopher P.; Bourassa, Alexandre; Miao, Kevin C.; Wolfowicz, Gary; Mintun, Peter J.; Crook, Alexander L.; Abe, Hiroshi; Ul Hassan, Jawad; Son, Nguyen T.; Ohshima, Takeshi; et al (December 2019, Science)

   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. Native Point Defect Measurement and Manipulation in ZnO Nanostructures

   https://doi.org/https://doi.org/10.3390/ma12142242  

   L.J. Brillson, J. W. (January 2019, Materials)

   This review presents recent research advances in measuring native point defects in ZnO nanostructures, establishing how these defects aect nanoscale electronic properties, and developing new techniques to manipulate these defects to control nano- and micro- wire electronic properties.From spatially-resolved cathodoluminescence spectroscopy, we now know that electrically-active native point defects are present inside, as well as at the surfaces of, ZnO and other semiconductor nanostructures. These defects within nanowires and at their metal interfaces can dominate electrical contact properties, yet they are sensitive to manipulation by chemical interactions, energy beams, as well as applied electrical fields. Non-uniform defect distributions are common among semiconductors, and their eects are magnified in semiconductor nanostructures so that their electronic eects are significant. The ability to measure native point defects directly on a nanoscale and manipulate their spatial distributions by multiple techniques presents exciting possibilities for future ZnO nanoscale electronics. 

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4. Local well‐posedness of the higher‐order nonlinear Schrödinger equation on the half‐line: Single‐boundary condition case

   https://doi.org/10.1111/sapm.12642  

   Alkın, Aykut; Mantzavinos, Dionyssios; Özsarı, Türker (January 2024, Studies in Applied Mathematics)

   Abstract We establish local well‐posedness in the sense of Hadamard for a certain third‐order nonlinear Schrödinger equation with a multiterm linear part and a general power nonlinearity, known as higher‐order nonlinear Schrödinger equation, formulated on the half‐line . We consider the scenario of associated coefficients such that only one boundary condition is required and hence assume a general nonhomogeneous boundary datum of Dirichlet type at . Our functional framework centers around fractional Sobolev spaces with respect to the spatial variable. We treat both high regularity () and low regularity () solutions: in the former setting, the relevant nonlinearity can be handled via the Banach algebra property; in the latter setting, however, this is no longer the case and, instead, delicate Strichartz estimates must be established. This task is especially challenging in the framework of nonhomogeneous initial‐boundary value problems, as it involves proving boundary‐type Strichartz estimates that are not common in the study of Cauchy (initial value) problems. The linear analysis, which forms the core of this work, crucially relies on a weak solution formulation defined through the novel solution formulae obtained via the Fokas method (also known as the unified transform) for the associated forced linear problem. In this connection, we note that the higher‐order Schrödinger equation comes with an increased level of difficulty due to the presence of more than one spatial derivatives in the linear part of the equation. This feature manifests itself via several complications throughout the analysis, including (i) analyticity issues related to complex square roots, which require careful treatment of branch cuts and deformations of integration contours; (ii) singularities that emerge upon changes of variables in the Fourier analysis arguments; and (iii) complicated oscillatory kernels in the weak solution formula for the linear initial‐boundary value problem, which require a subtle analysis of the dispersion in terms of the regularity of the boundary data. The present work provides a first, complete treatment via the Fokas method of a nonhomogeneous initial‐boundary value problem for a partial differential equation associated with a multiterm linear differential operator. 

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5. Spin-defect qubits in two-dimensional transition metal dichalcogenides operating at telecom wavelengths

   https://doi.org/10.1038/s41467-022-35048-0  

   Lee, Yeonghun; Hu, Yaoqiao; Lang, Xiuyao; Kim, Dongwook; Li, Kejun; Ping, Yuan; Fu, Kai-Mei C.; Cho, Kyeongjae (December 2022, Nature Communications)

   Abstract Solid state quantum defects are promising candidates for scalable quantum information systems which can be seamlessly integrated with the conventional semiconductor electronic devices within the 3D monolithically integrated hybrid classical-quantum devices. Diamond nitrogen-vacancy (NV) center defects are the representative examples, but the controlled positioning of an NV center within bulk diamond is an outstanding challenge. Furthermore, quantum defect properties may not be easily tuned for bulk crystalline quantum defects. In comparison, 2D semiconductors, such as transition metal dichalcogenides (TMDs), are promising solid platform to host a quantum defect with tunable properties and a possibility of position control. Here, we computationally discover a promising defect family for spin qubit realization in 2D TMDs. The defects consist of transition metal atoms substituted at chalcogen sites with desirable spin-triplet ground state, zero-field splitting in the tens of GHz, and strong zero-phonon coupling to optical transitions in the highly desirable telecom band. 

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