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14. Heteroepitaxial β‐Ga2O3 on Conductive Ceramic Templates: Toward Ultrahigh Gain Deep‐Ultraviolet Photodetection.

Author

Alfaraj, Nasir, Li, Kuang‐Hui, Alawein, Meshal, Kang, Chun Hong, Braic, Laurentiu, Zoita, Nicolae Catalin, Kiss, Adrian Emil, Ng, Tien Khee, and Ooi, Boon S.

Subjects
*ACTION spectrum, *DECAY constants, *TITANIUM nitride, *CERAMICS, *SINGLE crystals, *NITRIDES, *TIN
Abstract

This article investigates the ultrahigh sensitivity and DUV photodetection capability of a hybrid oxide‐nitride stack comprising β‐Ga2O3 layers grown heterogeneously on a conductive ceramic crystal. The ceramic crystal, namely a TiN interlayer, which acts as a lattice template, was heteroepitaxially grown on bulk MgO. Because β‐Ga2O3 is a monoclinic phase crystal, it is conjectured that its nucleation and growth process on cubic phase TiN is entropic in nature, whereby the two unit cell configurations of the β‐Ga2O3 crystal, exhibiting rotational twin domains, grew alternately side by side in a semiperiodic manner on TiN while maintaining a single crystal phase. This film formation mechanism contributed to the introduction of additional defects in the β‐Ga2O3 lattice (Taylor's dislocations in addition to growth‐induced vacancies). The fabricated DUV photodetectors based on the resulting metal‐semiconductor junction heterodiodes exhibited an average peak spectral responsivity of 276.72 A W−1 and fast decay constants in the order of 500 ms in the ultraviolet‐C regime, with true solar‐blind characteristics manifested by ultraviolet‐to‐visible rejection ratios of up to 2 × 103 and illuminating power density of around 70 μW cm−2. The crystallographic orientation relationships between the TiN and β‐Ga2O3 crystals, as well as the lattice fit and dislocation types, are revealed and examined. [ABSTRACT FROM AUTHOR]

Published
2021
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15. Deep-Ultraviolet Optoelectronic Devices Enabled by the Hybrid Integration of Next-Generation Semiconductors and Emerging Device Platforms

Author

Alfaraj, Nasir

Abstract

In this dissertation, the design and fabrication of deep-ultraviolet photodetectors were investigated based on gallium oxide and its alloys, through the heterogeneous integration with metallic and other inorganic materials. The crystallographic properties of oxide films grown directly and indirectly on silicon, magnesium oxide, and sapphire are examined, and the challenges that hinder the realization of efficient and reliable deep-ultraviolet photodetectors are described. In recent years, single-crystalline heterojunction photodiodes employing beta-polymorph gallium oxide thin films as the main absorption layers have been studied. However, reports in the literature generally lack a thorough examination of epitaxial growth processes of high-quality single-crystalline beta-polymorph gallium oxide thin films on metals, such as transition metal nitrides. My research was initiated by demonstrating an ultraviolet-C photodetector based on an amorphous aluminum gallium oxide photoconductive layer grown directly on (100)-oriented silicon. The solar-blind photodetector exhibited a peak spectral responsivity of 1.17 A/W. This is the first reported gallium oxide-based photodetector to have been grown and fabricated directly on silicon. The growth of high-quality monoclinic crystals on cubic silicon is a challenging process, which is largely due to the large lattice mismatch that compromises the crystal quality of the oxide layer, and leads to the degradation of device performance. This issue was addressed by growing the material on substrates with metal nitride templates, which resulted in improvements to the oxide crystal quality. Consequently, high optical gain ultraviolet-C photodetectors were fabricated based on a beta-polymorph gallium oxide photoconductive layer grown on magnesium oxide and silicon substrates with titanium nitride templates. The enhanced solar-blind photodetectors exhibited peak spectral responsivity levels as high as 276 A/W. Moreover, thin polymorphic gallium oxide films were grown on c-plane sapphire using pulsed laser deposition for the first time. The stacked thin films, namely epsilon- and beta-polymorph gallium oxide, were sequentially grown under the same conditions. X-ray diffraction measurements and transmission electron microscopy micrographs confirmed a heteroepitaxially grown beta-polymorph gallium oxide on a heterogeneously nucleated epsilon-polymorph gallium oxide polymorphic heterostructure on c-plane sapphire, which had rocking-curve widths of 1.4° (β-Ga2O3 (−603)) and 0.6° (ε-Ga2O3 (006)).

Published
2019
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22. Functional integrity and stable high-temperature operation of planarized ultraviolet-A AlxGa1−xN/AlyGa1−yN multiple-quantum-disk nanowire LEDs with charge-conduction promoting interlayer

Author

Alhamoud, Abdullah A., primary, Alfaraj, Nasir, additional, Priante, Davide, additional, Janjua, Bilal, additional, Alatawi, Abdullah A., additional, Albadri, Abdulrahman M., additional, Alyamani, Ahmed Y., additional, Ng, Tien Khee, additional, and Ooi, Boon S., additional

Published
2019
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26. Enhanced electro-optic performance of surface-treated nanowires: origin and mechanism of nanoscale current injection for reliable ultraviolet light-emitting diodes

Author

Priante, Davide, primary, Tangi, Malleswararao, additional, Min, Jung-Wook, additional, Alfaraj, Nasir, additional, Liang, Jian Wei, additional, Sun, Haiding, additional, Alhashim, Hala H., additional, Li, Xiaohang, additional, Albadri, Abdulrahman M., additional, Alyamani, Ahmed Y., additional, Ng, Tien Khee, additional, and Ooi, Boon S., additional

Published
2018
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39. Thermodynamic photoinduced disorder in AlGaN nanowires

Author

Alfaraj, Nasir, primary, Muhammed, Mufasila Mumthaz, additional, Li, Kuang-Hui, additional, Janjua, Bilal, additional, Aljefri, Renad A., additional, Sun, Haiding, additional, Ng, Tien Khee, additional, Ooi, Boon S., additional, Roqan, Iman S., additional, and Li, Xiaohang, additional

Published
2017
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41. Influence of TMAl preflow on AlN epitaxy on sapphire

Author

Sun, Haiding, primary, Wu, Feng, additional, Park, Young Jae, additional, Al tahtamouni, T. M., additional, Li, Kuang-Hui, additional, Alfaraj, Nasir, additional, Detchprohm, Theeradetch, additional, Dupuis, Russell D., additional, and Li, Xiaohang, additional

Published
2017
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42. Photoinduced entropy of InGaN/GaN p-i-n double-heterostructure nanowires

Author

Alfaraj, Nasir, primary, Mitra, Somak, additional, Wu, Feng, additional, Ajia, Idris A., additional, Janjua, Bilal, additional, Prabaswara, Aditya, additional, Aljefri, Renad A., additional, Sun, Haiding, additional, Khee Ng, Tien, additional, Ooi, Boon S., additional, Roqan, Iman S., additional, and Li, Xiaohang, additional

Published
2017
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47. Reversibly Bistable Flexible Electronics

Author

Alfaraj, Nasir

Subjects
Hardware_INTEGRATEDCIRCUITS
Abstract

Introducing the notion of transformational silicon electronics has paved the way for integrating various applications with silicon-based, modern, high-performance electronic circuits that are mechanically flexible and optically semitransparent. While maintaining large-scale production and prototyping rapidity, this flexible and translucent scheme demonstrates the potential to transform conventionally stiff electronic devices into thin and foldable ones without compromising long-term performance and reliability. In this work, we report on the fabrication and characterization of reversibly bistable flexible electronic switches that utilize flexible n-channel metal-oxide-semiconductor field-effect transistors. The transistors are fabricated initially on rigid (100) silicon substrates before they are peeled off. They can be used to control flexible batches of light-emitting diodes, demonstrating both the relative ease of scaling at minimum cost and maximum reliability and the feasibility of integration. The peeled-off silicon fabric is about 25 µm thick. The fabricated devices are transferred to a reversibly bistable flexible platform through which, for example, a flexible smartphone can be wrapped around a user’s wrist and can also be set back to its original mechanical position. Buckling and cyclic bending of such host platforms brings a completely new dimension to the development of flexible electronics, especially rollable displays.

Published
2015
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