LIGHT EMITTING DEVICES Nano-LED could support multi-Gbit/s on chip traffic PBy Julien Happich hotonics is a hot topic when it comes to increasing inter-chip and on-chip traffic between different processor or memory blocks. So far, microwaveguides, light modulator, outcoupling gratings and photodetectors have been successfully integrated, but designing suitable micro-scale light sources has proved to be challenging. In a paper titled “Waveguidecoupled nanopillar metal-cavity light-emitting diodes on silicon” just published in Nature Communications, researchers from the Eindhoven University of Technology demonstrated a nanoscale III–V LED layer stack bonded to a silicon substrate and coupled to an InP-membrane waveguide leading to a grating coupler. Taking the shape of a sub-micron sized nano-pillar, the nano- LED was characterized to be 1000 times more efficient than its predecessors, with an output power in the order of a few nW at room temperature, compared to outputs in pW reported in literature. According to the paper, the device showed a relatively high on-chip external quantum efficiency (10−4 to 10−2 for roomtemperature and 9.5 K, respectively). At low temperature, the researchers reported a power level above 50nW, corresponding to over 400 photons per bit at 1Gb/s, “far above the shot-noise limited sensitivity of an ideal receiver”, they wrote. Working at telecommunications wavelengths (1.55 μm), the device was successfully modulated using a pulse pattern generator at frequencies up to 5GHz. “With the expected low loss of short-distance interconnects and continuous progress in integrated receivers, this power level may enable intrachip data communications with an ultracompact source”, they note. The researchers have also developed a surface passivation method that could further boost the efficiency of the nano-LED 100-fold, while energy consumption could be further reduced by improving the ohmic contacts. The reality The new ¸RTO Meet demanding challenges with the ¸RTO2000 (600 MHz to 6 GHz): ❙ Quickly find signal faults with 1 Million waveforms/s ❙ Zone trigger easily isolates events in time or frequency domain ❙ Multi-channel spectrum analysis for correlated analysis ❙ Fast operation with SmartGrid and capacitive touch Multi Domain Visit us at Embedded World in Nuremberg March 14 to 16 Hall 4, Booth 4-218 For more information: www.scope-of-the-art.com/ad/rto Turn your signals into success. www.electronics-eetimes.com Electronic Engineering Times Europe March 2017 15 15351.052_RTO2000_EETimesEurope-März17_91x277_e_page2.indd 1 15.02.17 9:21 Uhr A SEM-picture of the new nano-LED showing the fabricated device structure before metallization. The nanopillar LED lies on top of a waveguide connected to a grating coupler. Schematic representation of the nanopillar LED on a silicon substrate. The layer stack from top to bottom is: n-InGaAs(100 nm)/n-InP(350 nm)/ InGaAs(350 nm)/p-InP(600 nm)/pnGaAsP( 200 nm)/InP(250 nm)/SiO2/BCB/ SiO2/Si.
EETE MAR 2017
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