Photodetection Properties of Nonpolar a‐Plane GaN Grown by Three Approaches Using Plasma‐Assisted Molecular Beam Epitaxy
TL;DR: In this article, a-plane GaN thin films are grown on r-plane sapphire using three different growth approaches by plasma-assisted molecular beam epitaxy (PAMBE) and in situ reflection high-energy electron diffraction (RHEED) analysis is performed during and after the growth to monitor the growth mode.
Abstract: Present work focuses on improving the quality of nonpolar a-plane GaN thin films by introducing unconventional new efficient growth conditions without compromising their UV photodetection properties. These epitaxial thin films are grown on r-plane sapphire using three different growth approaches by plasma-assisted molecular beam epitaxy (PAMBE). In situ reflection high-energy electron diffraction (RHEED) analysis is performed during and after the growth to monitor the growth mode, and it is found that the films assumed desired 2D mode during the growth. The crystalline quality and the phase purity of the films are assessed with the help of high-resolution X-ray diffraction and Raman spectroscopy. All the films are found to contain compressive stress, which indicate that all the films are strained and epitaxial. The temporal response is carried out in all the three batches, which is very stable. Sensitivity, responsivity, transit time, and gain values are estimated. Highest responsivity and the corresponding gain are found to be around 25 AW(-1), 86.47 at 1 V bias, respectively. These are the highest reported values so far for a-plane GaN at such low voltages.
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19 Mar 2020
TL;DR: By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized as mentioned in this paper, which is a self-powered and ultrafast approach.
Abstract: By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here, we report a self-powered and ultrafast pho...
36 citations
21 Feb 2020
TL;DR: In this paper, a-GaN was grown on r-sapphire and interdigitated electro-electromagnetic (EM) electrodes. But the properties of nonpolar a-plane GaN are superior along the [0002] azimuth direction compared to other azimath directions.
Abstract: Optoelectronic properties of nonpolar a-plane GaN are superior along the [0002] azimuth direction compared to other azimuth directions. We have grown a-GaN on r-sapphire, and interdigitated electro...
27 citations
TL;DR: In this article, the authors focus on the advancements in III-nitride-based photodetectors and their promising potentials for self-powered, broadband, and ultrafast photodetsectors using hybrid III-nodes/2D interfaces.
Abstract: Energy consumption is one of the most important aspects of any electronic device which needs further improvements in order to achieve a better sustainable future. This is equally true for commercially available photodetectors, which consume a lot of energy by using huge external bias voltage. So far, thin films have been widely used for photodetection of various bands of electromagnetic radiation. The only property which holds them back is the slower performance and lower responsivity compared to nanostructure-based devices. However, the disadvantage associated with nanostructure-based photodetectors is that they lack scalability for mass production or commercialization, due to the complex and expensive device fabrication steps. One of the plausible solutions for this limitation could be the use of hybrid structures, which are the combination of high-quality crystal materials such as ZnO, (Al, Ga, In)N, and GaAs with 2D materials consisting of MoS2, graphene, WSe2, and SnS2. This would provide extensive control over bandgap engineering, which could be used for scalable modular device fabrication. These approaches promise the development of photodetectors with relatively higher responsivities as well as self-powered photodetection. The current perspective focuses on the advancements in III-nitride-based photodetectors and their promising potentials for self-powered, broadband, and ultrafast photodetectors using hybrid III-nitride/2D interfaces.
24 citations
TL;DR: A nonpolar GaN metal–semiconductor–metal (MSM) photodetector (PD) with an ultrahigh responsivity and an ultrafast response speed in the ultraviolet spectral region is reported, which was fabricated on nonp polar GaN stripe arrays with a major improvement in crystal quality grown on patterned silicon substrates by means of using the two-step processes.
Abstract: This article reports a nonpolar GaN metal-semiconductor-metal (MSM) photodetector (PD) with an ultrahigh responsivity and an ultrafast response speed in the ultraviolet spectral region, which was fabricated on nonpolar (1120) GaN stripe arrays with a major improvement in crystal quality grown on patterned (110) silicon substrates by means of using our two-step processes. Our nonpolar GaN MSM-PD exhibits a responsivity of 695.3 A/W at 1 V bias and 12628.3 A/W at 5 V bias, both under 360 nm ultraviolet illumination, which are more than 20 times higher and 4 orders of magnitude higher compared to the current state-of-the-art photodetector, respectively. The nonpolar GaN MSM-PD displays a rise time and a fall time of 66 and 43 μs, respectively, which are 3 orders of magnitude faster compared to the current state-of-the-art photodetector.
16 citations
TL;DR: In this paper, the authors report the band discontinuities at the MoS2/III-nitride (InN, GaN, and AlN) heterointerfaces.
Abstract: Heterojunction band offset parameters are critical for designing and fabricating junction-based devices as these parameters play a crucial role in determining the optical and electronic properties of a device. Herein, we report the band discontinuities at the MoS2/III-nitride (InN, GaN, and AlN) heterointerfaces. Few-layer MoS2 thin films are deposited by pulsed laser deposition on III-nitrides/c-sapphire substrates. Band offsets [valence band offset (VBO) and conduction band offset (CBO)] at the heterojunctions are determined by high-resolution x-ray photoelectron spectroscopy. The estimated band alignments are found to be type-I (VBO: 2.34 eV, CBO: 2.59 eV), type-II (VBO: 2.38 eV, CBO: 0.32 eV), and type-III (VBO: 2.23 eV, CBO: 2.87 eV) for MoS2/AlN, MoS2/GaN, and MoS2/InN, respectively. Such determination of the band offsets of 2D/3D heterojunctions paves a way to understand and design the futuristic photonic and electronic devices using these material systems.
14 citations
References
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TL;DR: Developing UV-protective approaches based on a detailed understanding of molecular events that occur after UV exposure, focusing particularly on epidermal melanization and the role of the MC1R in genome maintenance are targeted.
Abstract: UV radiation (UV) is classified as a "complete carcinogen" because it is both a mutagen and a non-specific damaging agent and has properties of both a tumor initiator and a tumor promoter. In environmental abundance, UV is the most important modifiable risk factor for skin cancer and many other environmentally-influenced skin disorders. However, UV also benefits human health by mediating natural synthesis of vitamin D and endorphins in the skin, therefore UV has complex and mixed effects on human health. Nonetheless, excessive exposure to UV carries profound health risks, including atrophy, pigmentary changes, wrinkling and malignancy. UV is epidemiologically and molecularly linked to the three most common types of skin cancer, basal cell carcinoma, squamous cell carcinoma and malignant melanoma, which together affect more than a million Americans annually. Genetic factors also influence risk of UV-mediated skin disease. Polymorphisms of the melanocortin 1 receptor (MC1R) gene, in particular, correlate with fairness of skin, UV sensitivity, and enhanced cancer risk. We are interested in developing UV-protective approaches based on a detailed understanding of molecular events that occur after UV exposure, focusing particularly on epidermal melanization and the role of the MC1R in genome maintenance.
1,240 citations
TL;DR: In the clinic, artificial lamps emitting UVB and UVA radiation in combination with chemical drugs are used in the therapy of many skin diseases including psoriasis and vitiligo, and although such therapy is beneficial, it is accompanied with undesirable side effects.
1,045 citations
TL;DR: In this paper, a GaN multi-quantum well-structure laser diodes with Al0.14Ga0.86N/GaN modulation doped strained-layer superlattice cladding layers grown on an epitaxially laterally overgrown GaN (ELOG) substrate was demonstrated to have a lifetime of more than 1150 h under room-temperature continuous-wave operation.
Abstract: InGaN multi-quantum-well-structure laser diodes with Al0.14Ga0.86N/GaN modulation doped strained-layer superlattice cladding layers grown on an epitaxially laterally overgrown GaN (ELOG) substrate was demonstrated to have a lifetime of more than 1150 h under room-temperature continuous-wave operation. After 4 μm etching of the ELOG substrate, the etch pit density was about 2×108 cm2 in the region of the 4-μm-wide stripe window, but almost zero in the region of the 7-μm-wide SiO2 stripe.
797 citations
TL;DR: A comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field are provided.
Abstract: Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of high responsivity, high thermal stability, robust radiation hardness and high response speed. On the other hand, one-dimensional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga2O3, GaN, ZnO, or other metal-oxide nanostructures, also show their potential for high-efficiency UV photodetection. In some cases such as flame detection, high-temperature thermally stable detectors with high performance are required. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field. A special focus is given on the thermal stability of the developed devices, which is one of the key characteristics for the real applications.
650 citations
TL;DR: It is shown that the tip of an atomic force microscope can be used to pattern polarization domains in a thin film of lead zirconate titanate in high electric fields similar to those for field emission tips.
Abstract: We demonstrate a highly reproducible control of local electron transport through a ferroelectric oxide via its spontaneous polarization. Electrons are injected from the tip of an atomic force microscope into a thin film of lead-zirconate titanate, Pb(Zr0.2Ti0.8)O3, in the regime of electron tunneling assisted by a high electric field (Fowler-Nordheim tunneling). The tunneling current exhibits a pronounced hysteresis with abrupt switching events that coincide, within experimental resolution, with the local switching of ferroelectric polarization. The large spontaneous polarization of the PZT film results in up to 500-fold amplification of the tunneling current upon ferroelectric switching. The magnitude of the effect is subject to electrostatic control via ferroelectric switching, suggesting possible applications in ultrahigh-density data storage and spintronics.
451 citations