GaN/AlGaN multiple quantum wells grown on transparent and conductive (-201)-oriented β-Ga2O3 substrate for UV vertical light emitting devices

ACS Appl. Mater. Interfaces

et al. 2019

Self Cite

All-inorganic lead halide perovskites are promising materials for many optoelectronic applications. However, two issues that arise during device fabrication hinder their practical use, namely inadequate continuity of coated inorganic perovskite films across large areas and inability to integrate these films with traditional photolithography due to poor adhesion to wafers. Herein, for the first time, to address these issues, we show a room-temperature synthesis process employed to produce of CsPbBr 3 perovskite nanocrystals with twodimensional (2D) nanosheet features. Due to the unique properties of these 2D nanocrystals, including the "self-assembly" characteristic, and "double solvent evaporation inducing selfpatterning" strategy are used to generate high-quality patterned thin films in selected areas automatically after-drop-casting, enabling fabrication of high-performance devices without using complex and expensive fabrication processing techniques. The films are free from

Section: Resultssupporting

confidence: 91%

Self-Patterned CsPbBr₃ Nanocrystals for High-Performance Optoelectronics

Xin

Pak

ACS Appl. Mater. Interfaces

et al. 2019

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“…TRPL results indicated that the total lifetime was dominated by the slow decay component, which is indicative of highquality materials. Based on the available literature, the fast decay component is dominant in materials characterized by low crystal quality, [53,54] as it has been attributed to hot carrier−phonon interactions and optical phonon decay.…”

Section: Advanced Optical Analysis and The Band Structurementioning

confidence: 99%

“…To understand such carrier lifetime behavior in both materials, radiative and non-radiative components were analyzed, [51,54,55] and the results are reported in Figure 3e,f. As shown in Figure 3d, the lifetime of CsPbBr 3 at RT was dominated by radiative recombination (as it is in the same ns range of the total lifetime).…”

Section: Advanced Optical Analysis and The Band Structurementioning

confidence: 99%

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

Xin

Alaal

et al. 2020

Small

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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.

“…Further advances in the field of DUV optoelectronics are hindered by other issues, such as the difficulty in developing new cost‐effective material production and fabrication methods that could replace the expensive and high vacuum‐based technologies presently in use. Thus, as DUV‐WBGS based devices tend to be prohibitively expensive, they are difficult to produce on a large scale . Moreover, the defects in the interface between layers, such as lattice mismatch and dislocation defects, significantly hinder the performance of DUV devices .…”

mentioning

confidence: 99%

Novel P‐Type Wide Bandgap Manganese Oxide Quantum Dots Operating at Deep UV Range for Optoelectronic Devices

Advanced Optical Materials

Pak

Alaal

et al. 2019

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in a wide range of industrial applications, such as homeland security, medical diagnostics, food curing, sanitation, chemical and biological threat detection, space-tospace communications, missile detection, military surveillance, target detection and acquisition, transparent thin-film transistors, solar cells, white lighting, sterilization, medical treatment, and touch display panels. [1][2][3][4][5][6][7] For example, the most commercial DUV photodetectors are produced using UV-enhanced narrow bandgap semiconductors, mainly Si-based photodetector. [8,9] However, the narrow bandgap materials are ineffective in rejecting signals in the UV−vis−IR spectral region, making them unsuitable for DUV applications. Thus, high-quality DUV WBGSs are still needed to produce high-performance DUV optoelectronic devices. In each of the aforementioned fields, scientists and industry practitioners are looking to overcome different challenges. There is a growing demand for both p-type and n-type WBGSs that possess good stability and conductivity. The main obstacle to the achievement of this goal stems from the lack of p-type wide bandgap materials operating in the DUV range below 300 nm (i.e., >4.1 eV) that exhibit good p-type stability. Currently, the p-type materials having bandgap in the UV-A range (such as p-type GaN, Cu 2 O, and SnO) are utilized in DUV optoelectronics, which severely downgrade device performance, as their bandgaps are limited to the UV-A-to-visible spectral region (320-400 nm). [10,11] Moreover, though n-type WBGSs (e.g., ZnO, Ga 2 O 3 , and AlGaN) with good conductivity and stability can operate in the UV and DUV range (280−390 nm), it is not possible to convert them to a p-type material with good stability and conductivity due to their intrinsic electronic properties. [2,6,[11][12][13][14][15][16] Consequently, no highly stable conductive p-type DUV WBGS operating in both UV-B and UV-C region presently exists. [17] Further advances in the field of DUV optoelectronics are hindered by other issues, such as the difficulty in developing new cost-effective material production and fabrication methods that could replace the expensive and high vacuum-based technologies presently in use. Thus, as DUV-WBGS based devices tend Wide bandgap semiconductor (WBGS)-based deep UV (DUV) devices lag behind those operating in the visible and IR range, as no stable p-type WBGS that operates in the DUV region (<300 nm) presently exists. Here, solutionprocessed p-type manganese oxide WBGS quantum dots (MnO QDs) are explored. Highly crystalline MnO QDs are synthesized via femtosecond-laser ablation in liquid. The p-type nature of these QDs is demonstrated by Kelvin probe and field effect transistor measurements, along with density functional theory calculations. As proof of concept, a high-performance, self-powered, and solar-blind Schottky DUV photodetector based on such QDs is fabricated, which is capable of detecting under ambient conditions. The carrier collection efficiency is enhanced by asymmetric electrode structure, leadi...