Vacancy complexes induce long-range ferromagnetism in GaN

Zhang, Zhenkui; Schwingenschlögl, Udo; Roqan, Iman S.

doi:10.1063/1.4901458

Cited by 37 publications

(12 citation statements)

References 32 publications

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“…Ab Initio Electronic Structure Calculations of Different Phase CsPbX 3 : First principles-based DFT calculations were performed using VASP software package as it is very good tool to obtain the electronic properties and band structures [64,65] and other of the orthorhombic δ-CsPbI 3 (yellow phase), orthorhombic γ-CsPbI 3 (black phase), cubic CsPbI 3 , and cubic CsPbBr 3 . The electron-ion interaction was described by projected augmented wave (PAW) method.…”

Section: Methodsmentioning

confidence: 99%

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Xin

Alaal

Mitra

et al. 2020

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and military devices. Among these applications, medical diagnostics is particularly significant, but it presently requires direct exposure to high doses of radiation, which is harmful to human health, increasing cancer risk, especially in children. [1,2] Hence, X-ray detectors possessing both high sensitivity and high resolution with a low light interface noise [3,4] are required to minimize the radiation exposure during routine medical diagnostics. In the pertinent literature, use of conventional semiconductors for direct X-ray detection has been reported by several groups, including amorphous Se, [5] crystalline Si, [6] Ge, [7] HgI 2 , [8] CdTe, [9,10] and CdZnTe, [9,10] indicating that the most effective materials are indirect bandgap semiconductors [5-10] that exhibit low light interference noise. However, as such devices possess low sensitivity due to the low atomic number values of their materials, [7] as well as they still require expensive fabrication and complex processing methods, there is a high industrial demand for cost-effective highly sensitive X-ray detectors that are more suited for mass production. Ionic perovskite crystals can be processed from solution at low temperatures, in contrast to covalent bond semiconductors, which require a high-temperature crystallization process. Consequently, lead halogen perovskite has emerged as a promising candidate due to its cost-effectiveness, high crystal quality, high absorption cross-section, high illumination, and ability to form High-energy radiation detectors such as X-ray detectors with low light photoresponse characteristics are used for several applications including, space, medical, and military devices. Here, an indirect bandgap inorganic perovskite-based X-ray detector is reported. The indirect bandgap nature of perovskite materials is revealed through optical characterizations, time-resolved photoluminescence (TRPL), and theoretical simulations, demonstrating that the differences in temperature-dependent carrier lifetime related to CsPbX 3 (X = Br, I) perovskite composition are due to the changes in the bandgap structure. TRPL, theoretical analyses, and X-ray radiation measurements reveal that the high response of the UV/visible-blind yellow-phase CsPbI 3 under high-energy X-ray exposure is attributed to the nature of the indirect bandgap structure of CsPbX 3. The yellowphase CsPbI 3-based X-ray detector achieves a relatively high sensitivity of 83.6 μCGy air −1 cm −2 (under 1.7 mGy air s −1 at an electron field of 0.17 V μm −1 used for medical diagnostics) although the active layer is based solely on an ultrathin (≈6.6 μm) CsPbI 3 nanocrystal film, exceeding the values obtained for commercial X-ray detectors, and further confirming good material quality. This CsPbX 3 X-ray detector is sufficient for cost-effective device miniaturization based on a simple design.

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Section: Methodsmentioning

confidence: 99%

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Xin

Alaal

Mitra

et al. 2020

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“…It is well-known that bulk III-nitride compoundssuch as GaN, AlN, InN and their alloysare direct band-gap semiconductors that are used for a vast range of practical and reliable optoelectronic and electronic applications, such as lasers, light-emitting diodes, and transistors, − including devices operating in harsh environments, because of their unique mechanical and structural properties. − Moreover, the heterostructure of GaN nanosheets can potentially be beneficial in solar harvesting applications . Similar to bulk III nitrides, the two-dimensional (2D) GaN alloys have received tremendous research attention because of the possibility of tuning their optical properties, as their band gap can be tuned by generating GaN, AlN, and InN alloys .…”

Section: Introductionmentioning

confidence: 99%

Tuning the Electronic Properties of Hexagonal Two-Dimensional GaN Monolayers via Doping for Enhanced Optoelectronic Applications

Alaal

Roqan

2018

ACS Appl. Nano Mater.

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We explore structural, electronic and magnetic properties of two-dimensional (2D) gallium nitride (GaN) monolayer (ML) doped with different elements belonging to the groups III−VI, using density-functionaltheory (DFT) with the Perdew-Burke-Ernzerhof (PBE) functional and the screened hybrid functional (HSE06) approaches as well as molecular dynamics (MD) simulations. Dopant interactions in Ga-and Nrich environments are investigated by varying their concentrations from 1.38% to 5.5%. Our calculations reveal that oxygen and aluminium impurities are the most preferred candidates under Ga-and N-rich conditions, respectively. The electronic structure studies indicate that dopants containing an even number of valence electrons introduce magnetic behavior with spin-polarized properties, or n-type conductivity with nonmagnetic features, depending on the stoichiometric III/V ratio during growth. Dopants with an odd number of valence electrons modify the GaN ML band structure from indirect to direct bandgap at the Γ point, depending on dopant types at different III/V ratios as well as substitutional site. The calculated charge transfer explains the dopants' influence on the band structure and bond nature. The HSE calculations of doped g-GaN MLs show a 0.23−1.48 eV increase in the band gaps including the spin polarized band structures when compared with their PBE values. MD calculations suggest high structural stability at high growth temperatures. Such dopant-induced modifications in structural and physical properties of 2D GaN ML could potentially allow use of this material in diverse electronic, optoelectronic and spintronic applications.

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“…Such a superior performance obtained in this study can be due to several factors. (1) Both n-QD and p-micro-pyramid layers are WBG materials with a good band alignment and provide a greater surface-to-volume ratio compared to epitaxial films. ,,, (2) The inherent junction barrier within the QD network that can be modified by photogenerated carrier density increases the material conductance under DUV illumination as the junction barrier between QDs decreases with illumination, easing the carrier transient. ,,,,,, (3) As QDs are deposited on the micro-pyramids using the simple spray-coating method, the interface defects that are formed due to lattice mismatch during film heterostructure deposition of multi-layer devices are absent …”

Section: Resultsmentioning

confidence: 99%

Enhanced-Performance Self-Powered Solar-Blind UV-C Photodetector Based on n-ZnO Quantum Dots Functionalized by p-CuO Micro-pyramids

Alwadai

Mitra

Hedhili

et al. 2021

ACS Appl. Mater. Interfaces

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Smart solar-blind UV-C band photodetectors suffer from low responsivity in a self-powered mode. Here, we address this issue by fabricating a novel enhanced solar-blind UV-C photodetector array based on solution-processed n-ZnO quantum dots (QDs) functionalized by p-CuO micro-pyramids. Self-assembled catalyst-free p-CuO micro-pyramid arrays are fabricated on a pre-ablated Si substrate by pulsed laser deposition without a need for a catalyst layer or seeding, while the solution-processed n-ZnO QDs are synthesized by the femtosecond-laser ablation in liquid technique. The photodetector is fabricated by spray-coating ZnO QDs on a CuO micro-pyramid array. The photodetector performance is optimized via a p–n junction structure as both p-ZnO QDs and p-CuO micro-pyramid layers are characterized by wide band gap energies. Two photodetectors (with and without CuO micro-pyramids) are fabricated to show the role of p-CuO in enhancing the device performance. The n-ZnO QD/p-CuO micro-pyramid/Si photodetector is characterized by a superior photo-responsivity of ∼956 mA/W at 244 nm with a faster photoresponse (<80 ms) and 260 nm cut-off compared to ZnO QDs/Si photodetectors, confirming that the p-CuO micro-pyramids enhance the device performance. The self-powered photoresponse with a high photo-responsivity of ∼29 mA/W is demonstrated. These high-responsivity solar-bind UV-C photodetector arrays can be used for a wide range of applications.

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Vacancy complexes induce long-range ferromagnetism in GaN

Cited by 37 publications

References 32 publications

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Tuning the Electronic Properties of Hexagonal Two-Dimensional GaN Monolayers via Doping for Enhanced Optoelectronic Applications

Enhanced-Performance Self-Powered Solar-Blind UV-C Photodetector Based on n-ZnO Quantum Dots Functionalized by p-CuO Micro-pyramids

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Vacancy complexes induce long-range ferromagnetism in GaN

Cited by 37 publications

References 32 publications

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX3 Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX3 Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Tuning the Electronic Properties of Hexagonal Two-Dimensional GaN Monolayers via Doping for Enhanced Optoelectronic Applications

Enhanced-Performance Self-Powered Solar-Blind UV-C Photodetector Based on n-ZnO Quantum Dots Functionalized by p-CuO Micro-pyramids

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Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors

Identifying Carrier Behavior in Ultrathin Indirect‐Bandgap CsPbX₃ Nanocrystal Films for Use in UV/Visible‐Blind High‐Energy Detectors