Compatible with Si-CMOS nano column LED allows photon integration more accurate

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.

The position of the InP nanorod arrays can be controlled at 460 DEG C growth in the low magnification SEM image of all images in the scale corresponding to a of 10 m and 1 m, 4 m and a growth period of M (spacing)

The researchers first start from a clean silicon wafer (111), the M-40 of the oxidation of the 140nm to the nanometer diameter of about 320nm in diameter at 350 degrees Celsius, with a spacing of 1 mu m to locate the nucleation site of the nano column. In order to make the silicon crystal surface become rough after chemical method, the InP nano structure is grown in the MOCVD cavity at the temperature of 450 DEG C to 460 DEG C. The researchers found that the cone angle of the nano column was obviously affected by the growth temperature, and the nano needle was produced at 450 DEG C, and it was almost vertical columnar structure at the temperature of 460 degrees celsius.

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 column MQW LED assembly

Due to the growth pattern of the core shell, the nanorods grow out of their nucleation sites and extend beyond the oxide opening, reaching the final diameter of about 1 m. Therefore, when the N doped core of the nanorods is directly contacted with the n-Si substrate, the P doped shell grows on the oxide shield, eliminating the shunt path from the P doped shell and the n-Si substrate. 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.

For the characterization of the nano columnar LED, the quantum efficiency of 1510nm and about 30% was carried out. Although the footprint of the nano column LED is small, it can output 4 W power, the researchers claimed that this is the highest output from the nano / nano LED can be achieved. In this build, due to the collection efficiency of only 5%, the available light output fell to 200nW.

Another interesting aspect of this study is that the component can produce optical gain with an electrical bias, and show a strong response in the reverse injection, which helps to achieve photonic integration on the chip.

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