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SEM micrographs: (a) array of nano-LEDs with NCs, a transparent Ni/ Au top contact and annealed Ti/Al/Ni/Au bottom contacts. (b) Nanocrystal (NC) positioned in the SiO 2 hole structure. (c) Fully integrated NC/nano-LED structures (green dots as guides to the eye) in the device layout suitable for DC and HF characterization. 69,75 Reproduced with permission from Mikulics et al., Appl. Phys. Lett. 108, 061107 (2016). Copyright 2016 AIP Publishing LLC.
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In this Perspective, we will introduce possible future developments on group III-nitride nano-LEDs, which are based on current achievements in this rapidly arising research-technological field. First, the challenges facing their fabrication and their characteristics will be reported. These developments will be set in a broader context with primary...
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... structure 70 or used for testing and characterization, in which they are integrated into a platform for simultaneous investigations in a bottom-up geometry. Possible applications will be described later in Secs. IV A and IV D. An example of hybrid nanocrystal/III-nitride nano-LEDs fully integrated in an HF device layout is presented in Fig. 9. This device concept can be principally used for future single photon emitters where, e.g., nano-diamond crystals with N-vacancies 71-73 serve as the secondary photon emitters. Furthermore, the technology developed is applicable to a large range of biological, analytical, and communication applications and is suitable for the large ...
Citations
... From the material point of view, a quantum well (QW) that is capable of emitting light is also capable of absorbing, modulating and harvesting light [1][2][3][4][5][6][7]. Since the QW diode has broad electroluminescence (EL) and responsivity spectra, the same QW active region generates an emission-detection overlap phenomenon when the QW diode functions as a light-emitting diode (LED) and a photodiode. ...
A quantum well (QW) diode that is capable of emitting light is also capable of absorbing light. In particular, the QW diode has broad electroluminescence and responsivity spectra and thus, a distinct spectral overlap exists, enabling the establishment of light communication using two identical QW diodes, namely, one as the transmitter and the other as the receiver. Here, we demonstrate a time-division multiplexing (TDM) wireless light communication using two identical green QW diodes that are defined by software as transmitter or receiver to achieve real-time underwater data transmission via the same optical channel. To further exploit this dual emission-detection characteristics, we unite energy conservation, gravitational field and energy diagram theory to arrive the conclusion that the gravitational field may play a key role in the irreversibility between light emission and detection of the QW diode.
... The QW diode has broad electroluminescence (EL) and responsivity spectra, and thus, the diode features an overlapping region between its EL and responsivity spectra, allowing the device to function as both a transmitter and a receiver to set up a light communication link. [1][2][3][4][5][6] Therefore, the diode is able to be modulated to encode information optically at the transmitter end, and consequently, another diode with the same QW structure can be used as the receiver and detect modulated light to decode information. Zhang et al. monolithically integrated QW-based transmitters, modulators, waveguides, splitters, receivers, and monitors into a tiny III-nitride chip to achieve in-plane light communication. ...
Owing to emission-detection spectral overlap, a quantum well (QW) diode can detect shorter-wavelength photons emitted from another diode sharing the same QW active region. Therefore, a wireless light communication system can be established by using identical QW diodes that function separately as transmitters and receivers. Here, we investigate the irreversibility between light emission and detection of the QW diode and present a time-division multiplexing (TDM) visible light communication (VLC) network using five identical blue QW diodes that are defined by software as transmitters or receivers to achieve real-time TDM-integrated interconnection via the same optical paths. These results indicate the great potential of realizing an advanced TDM VLC network for diverse applications.
... Hence, the application of the LMA is advantageous also in the fabrication of the singularly addressable nano-LED architecture, since the precise control of the EL intensity of all the individual devices reduces along the way the overall device power consumption as well as increases their lifetime as it was reported previously [60]. Nevertheless, LMA is not limited only to nano-LED devices, this technique can be applied also to transmistor based devices forming core components for optical computing [63,64]. The conditioning of LED devices plays [60] an important role also in the development of novel correlative characterization techniques as we already presented in our previous studies [60,62]. ...
LED devices are increasingly gaining importance in lithography approaches due to the fact that they can be used flexibly for mask-less patterning. In this study, we briefly report on developments in mask-free lithography approaches based on nano-LED devices and summarize our current achievements in the different building blocks needed for its application. Individually addressable nano-LED structures can form the basis for an unprecedented fast and flexible patterning, on demand, in photo-chemically sensitive films. We introduce a driving scheme for nano-LEDs in arrays serving for a singularly addressable approach. Furthermore, we discuss the challenges facing nano-LED fabrication and possibilities to improve their performance. Additionally, we introduce LED structures based on a hybrid nanocrystal/nano-LED approach. Lastly, we provide an outlook how this approach could further develop for next generation lithography systems. This technique has a huge potential to revolutionize the field and to contribute significantly to energy and resources saving device nanomanufacturing.
... High-resolution and high-luminance AR and VR display applications require LED chip sizes on the order of micrometers or submicrometers. Accordingly, significant efforts have been put into developing micro/nano-LED arrays consisting of tiny pixels in the submicrometer size regime [19][20][21][22][23]. The development of GaN-based nanorod LEDs is expected to provide a significant advancement in display technology, offering unparalleled brightness, resolution, and miniaturization. ...
We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions.
... From the material point of view, a quantum well (QW) that is capable of emitting light is also capable of absorbing, modulating and harvesting light [1][2][3][4][5][6][7]. Since the QW diode has broad electroluminescence (EL) and responsivity spectra, the same QW active region generates an emission-detection overlap phenomenon when the QW diode functions as a light-emitting diode (LED) and a photodiode. ...
A quantum well (QW) diode that is capable of emitting light is also capable of absorbing light. In particular, the QW diode has broad electroluminescence and responsivity spectra and thus, a distinct spectral overlap exists, enabling the establishment of light communication using two identical QW diodes, namely, one as the transmitter and the other as the receiver. Here, we demonstrate a time-division multiplexing (TDM) wireless light communication using two identical green QW diodes that are defined by software as transmitter or receiver to achieve real-time underwater data transmission via the same optical channel. To further exploit this dual emission-detection characteristics, we unite energy conservation, gravitational field and energy diagram theory to arrive the conclusion that the gravitational field may play a key role in the irreversibility between light emission and detection of the QW diode.
... [1][2][3][4][5] Many conventional mechanical sensors tend to be bulky and entail complex data acquisition processes, spurring significant research efforts in this domain. 6 Wang et al. realized a compact and robust gas sensor by integrating InGaN/GaN based blue LEDs. 7 Cho et al. presented a more advanced monolithic photoactivated gas sensor based on a nanowatt-level, ultra-low-power blue μLED platform (μLP). ...
The quantum well diode (QWD) performs a dual role, functioning both as an emitter and a detector due to its unique feature of spectral overlap between emission and detection spectra. This dual functionality positions QWDs as promising candidates in the realm of multifunctional sensors. Furthermore, the well-established maturity of optical fiber communication, grounded in its intrinsic property of total reflection, makes it an ideal transmission medium for QWD sensing signals. Leveraging the coexisting emission and detection capabilities of QWDs, we have constructed a sensing system in this article. This system utilizes a QWD, which is stimulated to emit light, with the emitted light traveling through a specified length of optical fiber. A specialized load-bearing film, featuring an aluminum membrane on its rear to act as a mirror and an object of known weight on its front, induces deformation in the film, thereby altering the characteristics of the reflected light. This modulated light is subsequently captured by the QWD via the optical fiber, enabling the computation of the weight of the object. In this article, the QWD's emission peak is around 522 nm, and its detection range extends from 370 to 530 nm. Furthermore, by employing the appropriate approach, integrating QWD with optical fibers can be extended to sensing and measuring various physical quantities such as temperature, solution concentration, wind speed, and more. The advantages of QWDs include cost-effectiveness, multifunctionality, portability, and environmental friendliness. This technology represents a promising avenue for sensor control in the era of the Internet of Things.
... 17 The emerging GaN-on-silicon platform has the potential to realize photonic integration owing to the excellent photoelectric and electrical performance of GaN-based materials. [18][19][20][21][22][23][24][25] Similar to the InP-based approach, photonics integration based on a GaN-on-silicon platform can provide complete active-passive optical devices. Due to the availability of large-sized silicon wafers and good substrate thermal conductivity, low cost and high power density can be expected. ...
... 74 Another approach to pushing past this limit using LEDs is emerging as the size of the microLEDs decreases toward nanoLEDs. [90][91][92] The sub-micron dimensions of nanoLEDs allow them to serve as spatially resolved light sources and pave the way for Nano Illumination Microscopy (NIM). 93,94 In this technique, spatially resolved light sources are used to scan a sample by sequentially illuminating the nanoLED array and recording the optical signal through the sample on highly sensitive image sensors. ...
MicroLEDs offer an extraordinary combination of high luminance, high energy efficiency, low cost, and long lifetime. These characteristics are highly desirable in various applications, but their usage has, to date, been primarily focused toward next-generation display technologies. Applications of microLEDs in other technologies, such as projector systems, computational imaging, communication systems, or neural stimulation, have been limited. In non-display applications which use microLEDs as light sources, modifications in key electrical and optical characteristics such as external efficiency, output beam shape, modulation bandwidth, light output power, and emission wavelengths are often needed for optimum performance. A number of advanced fabrication and processing techniques have been used to achieve these electro-optical characteristics in microLEDs. In this article, we review the non-display application areas of the microLEDs, the distinct opto-electrical characteristics required for these applications, and techniques that integrate the optical and electrical components on the microLEDs to improve system-level efficacy and performance.
... Recently, other optical devices, such as detectors and waveguides, have been proposed to be integrated on the same quantum well (QW) diode platform and implemented for applications such as on-chip visible light communication [15,16]. QW-based micro-and nano-light-emitting diodes (LEDs) have attracted great interest due to their excellent optoelectronic performance and have been studied extensively for various applications [17][18][19][20][21]. Oh et al. reported a dual heterojunction nanorod device that allows simultaneous light emission and detection [22]. ...
When an AlGaInP quantum well (QW) diode is biased with a forward voltage and illuminated with an external shorter-wavelength light beam, the diode is in a superposition state of both light emission and detection. The two different states take place simultaneously, and both the injected current and the generated photocurrent begin to mix. Here, we make use of this intriguing effect and integrate an AlGaInP QW diode with a programmed circuit. The AlGaInP QW diode with the dominant emission peak wavelength centered around 629.5 nm is excited by a 620-nm red-light source. The photocurrent is then extracted as a feedback signal to regulate the light emission of the QW diode in real time without an external or monolithically integrated photodetector, paving a feasible way to autonomously adjust the brightness of the QW diode for intelligent illumination in response to changes in the environmental light condition.
... Downscaling of Si-based devices was shown to be decisive to increase performance, expand functionalities and decrease production costs [1]. Along the same line, miniaturization of GaN three-dimensional structures like wires and fins has today become relevant for both electronic and photonic applications in order to profit from the wide-bandgap, the high electron mobility and the excellent thermal stability of the nitride semiconductors in nanoscale devices [2][3][4][5][6][7]. Specifically, ultrathin GaN nanowires (NWs) with diameters 20 nm are beneficial for achieving ultrafast switching in field-effect transistors [8,9], they can elastically relax large amounts of epitaxial strain [10][11][12][13], and they host dielectrically confined excitons up to room temperature [14]. ...
We introduce a facile route for the top-down fabrication of ordered arrays of GaN nanowires with aspect ratios exceeding 10 and diameters below 20 nm. Highly uniform thin GaN nanowires are first obtained by lithographic patterning a bilayer Ni/SiNxhard mask, followed by a combination of dry and wet etching in KOH. The SiNxis found to work as an etch stop during wet etching, which eases reproducibility. Arrays with nanowire diameters down to (33 ± 5) nm can be achieved with a uniformity suitable for photonic applications. Next, a scheme for digital etching is demonstrated to further reduce the nanowire diameter down to 5 nm. However, nanowire breaking or bundling is observed for diameters below ≈ 20 nm, an effect that is associated to capillary forces acting on the nanowires during sample drying in air. Explicit calculations of the nanowire buckling states under capillary forces indicate that nanowire breaking is favored by the incomplete wetting of water on the substrate surface during drying. The observation of intense nanowire photoluminescence at room-temperature indicates good compatibility of the fabrication route with optoelectronic applications. The process can be principally applied to any GaN/SiNxnanostructures and allows regrowth after removal of the SiNxmask.
