LED Si-CMOS compatible nano column allows more accurate photonic integration

University of California at Berkeley (UC Berkeley) the researchers demonstrate the use of Si-CMOS compatible optical lithography technology 35 (III-V) and nano LED column design, but also control the effective integration of photonic nano LED precise growth position - it is in the CMOS circuit, so as to realize the key elements of fast chip optical interconnect.

Researchers in the "ACS Photonics" published "to the telecom wavelength in a bright electroluminescence from silicon to achieve Chaowei type position control InP nano column LED" (Ultracompact Position-Controlled InP Nanopillar LEDs on Silicon with Bright Electroluminescence at Telecommunication Wavelengths) pointed out in an article, control the yield growth position reaches as high as 90%. Can realize the uniform indium phosphide on silicon (InP) nanorods array grown on CMOS compatible conditions: low temperature and without catalyst.

InP nanorod array position can be controlled at 460 DEG C when the growth of low magnification SEM all images in the scale corresponding to 10 m and 1 m, 4 m and 40 m growth cycle (spacing)

Researchers from the first silicon wafer clean (111), nano aperture 140nm at 350 DEG C to two oxidation deposition about 320nm in diameter, the nucleation site spacing 1 M-40 nano positioning column M. The researchers chemically make the silicon surface becomes rough, and then to 450 to 460 DEG C temperature in the MOCVD cavity growth of InP nanostructures. The researchers found that nano column cone angle is obviously affected by the growth temperature, produce nano needle at 450 DEG C, and under the temperature of 460 DEG C is almost perpendicular to the columnar structure.

The researchers based on the nano column, through the center of the core - the same shell (core-shell) growth of five in the active area of PN incorporated into the indium gallium arsenide diode in quantum well (InGaAs), n-InP/InGaAs MQW/p-InP/p-InGaAs LED nano electric drive.

Schematic diagram of nano MQW column LED component

The growth pattern of core - shell, nano column by its nucleation and growth position, and extended to the oxide aperture outside, final diameter reaches about 1 m. Therefore, when direct contact nano column n doped core and n-Si substrate, P doped oxide shell in shielding on growth, eliminated from the diversion path shell and n-Si substrate of P doped. 20/200nm Ti/Au by electron beam evaporation inclined to high P doped InGaAs contact layer, the completion of the assembly to form the electrical contacts, including nano column small area exposed, and no metal as a LED light output window.

Nano columnar LED characterization, was shot in the quantum efficiency of 1510nm and about 30% of the. Although the nano column LED occupying small space, but can output 4 W power, the researchers claim that this is from the highest light output records / nano structure of LED nanorods can be realized. In this implementation, the collection efficiency is only 5%, the light output available to 200nW.

Another interesting feature of the study is that the component can produce optical gain by electrical bias, and show a strong response in the reverse injection, which is helpful to the realization of photonic integration on a chip.

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