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The growing demand for ever-increasing optical communications capacity directly dictates the development of new generations of high-speed transmitters (50-100GBaud). In particular, for applications such as data centers and optical access networks, significant performance must be achieved while reducing production costs [1]. The strategy chosen by our 'Nokia Bell Labs France' teams, located at the III-V Lab in Palaiseau, is to produce very high-speed transmitters based on InP photonic integrated circuits (PICs). 

To achieve this performance, while increasing the manufacturing yield of optoelectronic components, the III-V Lab is equipped with several latest-generation MOVPE (Metal Organic Vapor Phase Epitaxy) growth reactors, with capacities ranging from 6x2“ to 5x4”, and in-situ optical characterization tools. This epitaxial growth technique is applied to the production of (Al)GaInAs(P)-based multi-quantum-well (MQW) heterostructures, which are at the heart of our optoelectronic components: Lasers (DFB), Amplifiers (SOA) & Modulators (EAM).

 

The aim of the internship is to exploit these optical signals to extract as much nanoscale material data as possible [2]. These results will also be compared with other types of ex-situ characterization used in routine mode, such as X-ray Diffraction and Photoluminescence. A database and calibration charts can be produced.

The candidate is expected to have:

A good knowledge of semiconductors; an understanding of the physical principles of optical measurements applied to materials A taste for experimental work in order to master different tools (epitaxy, cleanroom processes, characterization); data processing/handling skillsThe ability to adapt in order to interact closely with other teams, as well as with the manufacturer of the in-situ tool “LayTec” [3] A good level in English and FrenchFirst year of Master (Bac+4)

[1]        E. Harstead, D. Van Veen, V. Houtsma, and P. Dom, “Technology Roadmap for Time-Division Multiplexed Passive Optical Networks ( TDM PONs ),” vol. 37, no. 2, pp. 657–664, 2019.

[2]        Peter Wolfram, E. Steimetz, Willi Ebert, J. T. Zettler, Norbert Grote "Routine growth of InP based device structures using process calibration with optical in-situ techniques", Journal of Crystal Growth, vol. 272, no. 118-124, pp. 118-124, December 2004

[3]          https://www.laytec.de/epicurve

Thanks to the new optical tools available on MOVPE reactors, it is possible to extract maximum information from each layer of a heterostructure (between 30 and 180) in real time and non-destructively during growth. Optimizing the epitaxy process through rigorous optical control is the most effective way of reducing manufacturing costs while improving fine material quality.

Because reflectometry probes structures with different optical index layers, it reveals periodic Fabry-Perot-type undulations. The thickness and composition of each layer can be measured individually. Pyrometric measurements, corrected for emissivity by reflectometry, give an absolute value of surface temperature. Finally, very fine measurements of surface curvature can be used to measure the stresses involved and thus quantify alloy stoichiometry.