Si-CMOS compatible nano column LED can make photonic 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.

A low magnification SEM diagram with a position controllable InP nanorod array growing at 460 degrees. The scale in all images corresponds to 10 m and 1 m, 4 m and 40 mu m respectively (spacing)

The researchers started with a clean silicon wafer (111) and deposited two of the 140nm oxide at a temperature of about 320nm at a temperature of about 1 nm at 350 DEG C to locate the nucleation site of the nanorods at distances of between M and m-40. After chemically roughening the surface of the silicon, the researchers grew InP nanostructures in the MOCVD cavity at temperatures between 450 and 460 degrees celsius. The researchers found that the cone angle of the nanorods was significantly affected by the growth temperature, resulting in nano needles at 450 degrees Celsius, while the column structure was almost vertical at 460 degrees centigrade.

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 component

Because of the growth mode of the core shell, the nano column grows out of its nucleation site and extends beyond the oxide opening to achieve a final diameter of about 1 m. Thus, when the N doped core of the nano column is in direct contact 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.

Nano columnar LED was characterized at 1510nm and at a quantum efficiency of about 30%. Although the footprint of the nano column LED is small, it can output 4 W of power, and the researchers claim it is the highest light output recorded from the nano column / nanostructure LED. Under this setup, as the collection efficiency is only 5%, the available light output is reduced to 200nW.

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

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