May 18, 2024

Quantum Well Nanowire Array Micro-LEDs: The Future of On-chip Optical Communication

Secret to on-chip optical networks are miniaturized lights such as micro-/ light-emitting diodes or nano-scale lasers (LEDs). The majority of developments on micro-/ nano-LEDs are based on III-nitride material systems at noticeable wavelengths. There have actually been restricted reports on high-speed infrared micro-LEDs at telecommunication wavelengths, indispensable for the future development of Li-Fi innovation, photonic integrated circuits (PICs), and biological applications.
Epitaxial grown In( Ga) As( P)/ InP nanowires hold great prospective for miniaturized LEDs and lasers at telecommunication wavelength range, as their wide bandgap tunability might make it possible for monolithic combination of multi-wavelength lights on a single chip through a single epitaxial growth, which might increase the information transmission capacity by wavelength department multiplexing and multiple-input multiple-output innovations.
(a) Schematic of p-i-n InGaAs/InP single QW nanowire LED structure with vertical and lateral cross-sections. (b) 30 ° slanted view SEM image of the nanowire range with a pitch of 800 nm. (c) Cross-sectional HAADF-STEM image of a nanowire showing the hexagonal shape and radial QW under various magnifications.
Research study Demonstrations and findings
The authors of this short article show the selective-area growth and fabrication of extremely uniform p-i-n core-shell InGaAs/InP single quantum well (QW) nanowire variety LEDs. Figure 1 (a, b) reveals the schematic of the QW LED structure in a single nanowire and a scanning electron microscopic lense (SEM) picture of a nanowire selection with highly consistent morphology, respectively. The in-depth QW structure in the radial direction is further exposed by the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image in Figure 1( c). To penetrate the product composition of the QW, the energy dispersive X-ray spectroscopy analysis in Figure 1( d) was also performed, clearly revealing that the InGaAs QW area is gallium- and arsenic-rich compared to the InP barrier region.
Figure 2. (a) Schematic of produced nanowire array LED. (b) L-I and I-V curves of a representative nanowire selection LED. (c) Voltage-dependent EL spectra at space temperature. (d) Normalized voltage-dependent EL spectra from (c). (e) Simulated voltage-dependent spontaneous emission spectra. (f) Simulated emission spectrum at the bias of 1.2 V, revealing the decoupled contribution from radial and axial quantum wells. Credit: OES
The QW nanowire LEDs displayed strong bias-dependent electroluminescence (EL), shown in Figure 2 (c, d), covering telecommunication wavelengths (1.35 ~ 1.6 μm). 2 popular EL peaks can be identified from the spectra revealed in Figure 2( d), consisting of a long wavelength peak at ~ 1.5 μm originating from the radial QW and a brief wavelength peak at ~ 1.35 μm due to a combined emission from axial and radial QWs.
Figure 3: (a) Representative PL spectra determined from the top of the nanowire selections with different pitch sizes. (b) EL spectra determined at a forward bias of 1.5 V from nanowire range LED with different pitch sizes. (c) Peak wavelength of the bias-dependent EL spectra from nanowire selection LED with different pitch sizes.
Tunability and Applications
The multi-wavelength tunability of the QW nanowire range has actually been further shown through the monolithic growth of nanowire varieties with various pitch sizes (i.e., the center-to-center distance in between surrounding nanowires in a range) on the exact same substrate.
Figure 3 (a) shows the representative photoluminescence (PL) spectra collected from nanowire selections with various pitch sizes, revealing longer wavelength PL emission from larger pitch nanowire selections due to the increased QW density or indium incorporation into the QW.
The nanowire variety LEDs with pitch sizes of 0.8, 1.0, and 2.0 μm were then produced on the very same substrate, with the corresponding electroluminescence (EL) spectra at a predisposition of 1.5 V as revealed in Figure 3 (b), showing a constant pattern as in the PL spectra. The EL emission from bigger pitch nanowire variety LED was observed at a longer wavelength, with the peak wavelength of the bias-dependent EL spectra extended from ~ 1.57 μm (pitch 0.8 μm variety) to ~ 1.67 um (pitch 2.0 μm range), which covers the telecommunication C band.
Figure 3 (c) summarizes the bias-dependent (from 1 to 4 V) EL peak wavelength for all pitch sizes with more than 100 nm blueshift obtained for each case, indicating a broad emission wavelength tunability across the telecommunication wavelength regime.
The array-based QW nanowire LEDs also provide fantastic potential for more boosting the communication capacity by integrating multiple multi-wavelength LEDs with much-reduced sizes on the exact same chip to attain wavelength division multiplexing. As a proof of concept, multiple small-size micro-LED selections with pixel sizes less than 5 µm set up to the letters of “ANU” were grown under the same conditions used for big variety growth revealed in Figure 3( e). Several infrared cam pictures of several micro-LED varieties producing under different predispositions are presented in Figure 3( f), highlighting the pledge of integrating multiple multi-wavelength micro-LEDs on the same chip.
To conclude, the authors have actually shown selective area development and fabrication of highly consistent p-i-n core-shell InGaAs/InP single QW nanowire range micro-LEDs, with axial and radial QWs adding to the electroluminescence at wavelengths of ~ 1.35 and 1.5 μm, respectively. The electroluminescence spectra of the nanowire variety LED showed strong bias-dependent spectral shift due to the band-filling result, suggesting a voltage-controlled multi-wavelength (1.35– 1.6 μm) operation covering telecommunication wavelengths.
The fantastic compatibility of the nanowire variety LEDs with wavelength-division-multiplexing and multiple-input multiple-output technologies for high-speed interaction was additional shown by the monolithic growth and fabrication of nanowire range LEDs with various pitch sizes and much-reduced variety sizes (< < 5 μm in width) on the exact same substrate, as well as GHz-level modulation. This work provides a promising path for establishing nanoscale on-chip light sources for next-generation incorporated optical communication systems. Referral: "High-speed multiwavelength InGaAs/InP quantum well nanowire range micro-LEDs for next generation optical interactions" by Fanlu Zhang, Zhicheng Su, Zhe Li, Yi Zhu, Nikita Gagrani, Ziyuan Li, Mark Lockrey, Li Li, Igor Aharonovich, Yuerui Lu, Hark Hoe Tan, Chennupati Jagadish and Lan Fu, 26 June 2023, Opto-Electronic Science.DOI: 10.29026/ oes.2023.230003. Scientists have actually highlighted the capacity of on-chip nanophotonic systems as an option to the obstacles provided by conventional electrical networks. These systems use light for data transmission, providing increased bandwidth and speed. A new publication from Opto-Electronic Science summaries multiwavelength high-speed quantum well nanowire array micro-LED for next-generation on-chip optical communication. As the variety of cores in a processor continues to grow, so too does the obstacle of connecting them all together. Conventional electrical networks fall short due to latency, restricted bandwidth, and high power usage. Researchers have long sought a much better alternative, and on-chip nanophotonic systems have actually become a promising alternative to standard electrical networks. On-chip optical networks utilize light for information transmission, offering terrific benefits over electrical signals. Light, being faster than electrical power, can carry bigger amounts of information through multiplexing innovations. The authors of this article show the selective-area development and fabrication of extremely consistent p-i-n core-shell InGaAs/InP single quantum well (QW) nanowire array LEDs. Figure 1 (a, b) shows the schematic of the QW LED structure in a single nanowire and a scanning electron microscopic lense (SEM) image of a nanowire range with extremely uniform morphology, respectively. Figure 3: (a) Representative PL spectra determined from the top of the nanowire ranges with different pitch sizes. (b) EL spectra measured at a forward bias of 1.5 V from nanowire variety LED with various pitch sizes. (c) Peak wavelength of the bias-dependent EL spectra from nanowire variety LED with different pitch sizes.