low frequency (380 kHz) excitation plasma that enable intense bombardment of hydrogen, all seem to provide a combined active role in the passivation mechanism of the pillars by reducing the surface states.As a result, we observe up to a 29-fold increase of the photoluminescence (PL) integrated intensity for the best samples as compared to untreated nanopillars. X-ray photoelectron spectroscopy analysis confirms the best treatments show remarkable removal of gallium and arsenic native oxides. Time-resolved micro-PL measurements display nanosecond lifetimes resulting in a record-low surface recombination velocity of ~1.1×10 4 cm s -1 for dry etched GaAs nanopillars. We achieve robust, stable and long-term passivated nanopillar surfaces which creates expectations for remarkable high internal quantum efficiency (IQE>0.5) in GaAs nanoscale light-emitting diodes. The enhanced performance paves the way to many other nanostructures and devices such as miniature resonators, lasers, photodetectors and solar cells opening remarkable prospects for GaAs active nanophotonic devices.ultralow output powers (in the nW or even pW range), 3,10,11 which makes nanoLEDs challenging for practical optical systems. Taking the example of III-V nanopillars, and neglecting losses related with metallic structures in metal-dielectric or plasmonic nanocavites, the main reasons for the extremely low EQEs are two-fold. Firstly, coupling the light output efficiently to a nanowaveguide, 11 or a plasmonic waveguide, 3 remains a challenge when the area of the light source is reduced to the deep sub-µm. 2 Secondly, at these small scales non-radiative effects in III-V materials, specifically surface-related properties, become more important as the surface-to-volume ratio increases substantially. In this work, we devote our attention to the role of the non-radiative effects in the performance of III-V gallium arsenide (GaAs) light-emitting subwavelength devices.Among the wide range of III-V materials available for active nanophotonic devices, the GaAs/Al-GaAs is one of the most studied and a key compound material for photonics, 4,15-18 providing optical emission and absorption in a wide range of wavelengths spanning from the visible to near-infrared (NIR).GaAs has recently been notable in many photonic applications such as 3D sensing using GaAs-based lasers, NIR-LEDs and visible red-orange-yellow LEDs for displays. However, the surface of GaAs-based materials and their interfaces with dielectrics tend to host large densities of electronically active defects (or dangling bonds). 19 As a result, at ambient conditions, an oxide layer is formed on the surface of the GaAs (e.g. Ga2O3 and As2O3), which leads to charge trapping. 20 Importantly, when semiconductors are nanostructured, namely using top-down dry etching, the plasma reactive etching process can induce additional surface damages, 21 such as surface roughness due to ion bombardment, surface contamination due to polymer deposition, or surface stoichiometry change due to preferential etching. Overall...
Event-activated biological-inspired subwavelength (sub-λ) optical neural networks are of paramount importance for energy-efficient and high-bandwidth artificial intelligence (AI) systems. Despite the significant advances to build active optical artificial neurons using for example phase-change materials, lasers, photodetectors, and modulators, miniaturized integrated sources and detectors suited for few-photon spike-based operation and of interest for neuromorphic optical computing are still lacking. In this invited paper we outline the main challenges, opportunities, and recent results towards the development of interconnected neuromorphic nanoscale light-emitting diodes (nanoLEDs) as key-enabling artificial spiking neuron circuits in photonic neural networks. This method of spike generation in neuromorphic nanoLEDs paves the way for sub-λ incoherent neural circuits for fast and efficient asynchronous brain-inspired computation.
We report the first observation of pronounced light emission (~806 nm) from the active AlAs/GaAs/AlAs double barrier quantum well of unipolar (electron-transporting) microLEDs. This paves the way for a new class of n-type optoelectronic micro-nanodevices.
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