| 1. |
- Huang, Yuqing, et al.
(författare)
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Tuneable Nonlinear Spin Response in a Nonmagnetic Semiconductor
- 2023
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Ingår i: Physical Review Applied. - : AMER PHYSICAL SOC. - 2331-7019. ; 19:6
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear effects and dynamics are found in a wide range of research fields. In magnetic materials, nonlinear spin dynamics enables ultrafast manipulation of spin, which promises high-speed nonvolatile information processing and storage for future spintronic applications. However, a nonlinear spin response is not yet demonstrated in a nonmagnetic material that lacks strong magnetic interactions. Dilute nitride III-V materials, e.g., (Ga, N)As, have the ability to amplify the conduction-electron-spin polarization by filtering out minority spins via spin-polarized defect states at room temperature. Here, by employing coupled rate equations, we theoretically demonstrate the emergence of a nonlinear spin response in such a defect-enabled room-temperature spin amplifier. Furthermore, we showcase the proposed spin nonlinearity in a (Ga, N)As-InAs quantum dot (QD) coupled all-semiconductor nanostructure, by measuring the higher-harmonic generation, which converts the modulation of excitation polarization into the second-, third-, and fourth-order harmonic oscillations of the QDs photoluminescence intensity and polarization. The observed spin nonlinearity originates from defect-mediated spin-dependent recombination, which can be conveniently tuned with an external magnetic field and can potentially operate at a speed exceeding 1 GHz. The demonstrated spin nonlinearity could pave the way for nonlinear spintronic and optospintronic device applications based on nonmagnetic semiconductors with simultaneously achievable high operation speed and nonlinear response.
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| 2. |
- Mopoung, Kunpot, et al.
(författare)
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Understanding Antiferromagnetic Coupling in Lead-Free Halide Double Perovskite Semiconductors
- 2024
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 128:12, s. 5313-5320
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Tidskriftsartikel (refereegranskat)abstract
- Solution-processable semiconductors with antiferromagnetic (AFM) order are attractive for future spintronics and information storage technology. Halide perovskites containing magnetic ions have emerged as multifunctional materials, demonstrating a cross-link between structural, optical, electrical, and magnetic properties. However, stable optoelectronic halide perovskites that are antiferromagnetic remain sparse, and the critical design rules to optimize magnetic coupling still must be developed. Here, we combine the complementary magnetometry and electron-spin-resonance experiments, together with first-principles calculations to study the antiferromagnetic coupling in stable Cs-2(Ag:Na)FeCl6 bulk semiconductor alloys grown by the hydrothermal method. We show the importance of nonmagnetic monovalence ions at the B-I site (Na/Ag) in facilitating the superexchange interaction via orbital hybridization, offering the tunability of the Curie-Weiss parameters between -27 and -210 K, with a potential to promote magnetic frustration via alloying the nonmagnetic B-I site (Ag:Na ratio). Combining our experimental evidence with first-principles calculations, we draw a cohesive picture of the material design for B-site-ordered antiferromagnetic halide double perovskites.
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| 3. |
- Stehr, Jan Eric, et al.
(författare)
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Color center in ß-Ga2O3 emitting at the telecom range
- 2024
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 124:4
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal (TM) ions incorporated into a host from a wide bandgap semiconductor are recognized as a promising system for quantum technologies with enormous potential. In this work, we report on a TM color center in beta-Ga2O3 with physical properties attractive for quantum information applications. The center is found to emit at 1.316 mu m and exhibits weak coupling to phonons, with optically addressable higher-lying excited states, beneficial for single-photon emission within the telecom range (O-band). Using magneto-photoluminescence (PL) complemented by time-resolved PL measurements, we identify the monitored emission to be internal E-1 ->(3)A(2) spin-forbidden transitions of a 3d(8) TM ion with a spin-triplet ground state-a possible candidate for a spin qubit. We tentatively attribute this color center to a complex involving a sixfold coordinated Cu3+ ion.
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| 4. |
- Stehr, Jan Eric, 1981-, et al.
(författare)
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Effects of growth temperature and thermal annealing on optical quality of GaNAs nanowires emitting in the near-infrared spectral range
- 2020
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Ingår i: Nanotechnology. - : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 31:6
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Tidskriftsartikel (refereegranskat)abstract
- We report on optimization of growth conditions of GaAs/GaNAs/GaAs core/shell/shell nanowire (NW) structures emitting at ~1 μm, aiming to increase their light emitting efficiency. A slight change in growth temperature is found to critically affect optical quality of the active GaNAs shell and is shown to result from suppressed formation of non-radiative recombination (NRR) centers under the optimum growth temperature. By employing the optically detected magnetic resonance spectroscopy, we identify gallium vacancies and gallium interstitials as being among the dominant NRR defects. The radiative efficiency of the NWs can be further improved by post-growth annealing at 680 °C, which removes the gallium interstitials.
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| 5. |
- Stehr, Jan Eric, et al.
(författare)
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Magneto-optical properties of Cr3+ in beta-Ga2O3
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:5
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Tidskriftsartikel (refereegranskat)abstract
- beta-Ga2O3 is a wide bandgap semiconductor that is attractive for various applications, including power electronics and transparent conductive electrodes. Its properties can be strongly affected by transition metal impurities commonly present during the growth such as Cr. In this Letter, we determine the electronic structure of Cr3+ by performing a correlative study of magneto-photoluminescence (magneto-PL) and electron paramagnetic resonance. We unambiguously prove that the so-called R-1 and R-2 PL lines at around 1.79eV originate from an internal transition between the first excited state (E-2) and the (4)A(2) ground state of Cr3+. The center is concluded to have monoclinic local symmetry and exhibits a large zero-field splitting (similar to 147 mu eV) of the ground state, which can be directly measured from the fine structure of the R1 transition. Furthermore, g-values of the first excited state are accurately determined as g(a) = 1.7, g(b) = 1.5, and g(c*) = 2.1. Our results advance our understanding of the electronic structure of Cr in beta-Ga2O3 and provide a spectroscopic signature of this common residual impurity. (C) 2021 Author(s).
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