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PhD research proposal H/F : Growth of hexagonal crystal phase SiGe nanowires on m-plane substrates for integration of quantum electronics and photonics

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : vendredi 19 août 2022

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General information

Reference : UMR9001-LAEVIN-001
Workplace : PALAISEAU
Date of publication : Friday, July 29, 2022
Scientific Responsible name : Laetitia Vincent
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2022
Proportion of work : Full time
Remuneration : 2135 € gross salary per months

Description of the thesis topic

The hexagonal crystal phase of GeSi-2H (an allotrope of the standard cubic 3C structure) has emerged as
a revolutionary material which brings forward exciting photonic functionalities to the silicon technology.
SiGe-2H phase exhibits a direct band gap and an excellent light emission capabilities with a tuneable
emission wavelength in the mid infrared between 1.8-4.2 μm by a concentration range of 0-40% of Si.
We have pioneered the growth of Au-catalyzed
Ge-2H branches on wurtzite GaAs nanowires.
We have shown that the Ge branches grow in
the particular <1-100> direction on the (1-100)
sidewalls of the GaAs trunk. They exhibit the
wanted 2H crystal structure keeping an
epitaxial relationship with the GaAs trunk.
We aim at investigating the growth
mechanisms using in-situ and real time TEM
observations at the atomic scale and compare
Vapor-Solid-Solid (VSS) and Vapor-Liquid-Solid
(VLS) growth modes, which can be tuned by
the substrate temperature. It is important to
understand nucleation of this new material
system with the specific <1-100> orientation
and analyse the growth interface between the
branch and the catalyst. We will study the
crystal structure and defect formation as well as the formation of the cubic phase lateral overgrowth on
the (0001) sidewalls of the branches. This fundamental study will support the fabrication of axial Si/Ge
heterostructures along the unconventional <1-100> axis.
For scalable integration, nanowires must be grown on adequate hexagonal substrates with the specific
m-plane {1-100} surface. In a first attempt, we will use commercially available m-plane CdS substrates.
We will study the catalyst (Au and Sn) dewetting on CdS substrates and validate the possible growth of
GeSi-2H nanowires on CdS or on GaAs/CdS.
This study is part of ONCHIPS project funded by the EU Horizon-CL4-2021. In the global project we aim at
combining electronic and photonic qubits in the nanowires. We propose to grow enriched Ge quantum
dots acting as light emitting diode (LED) in Si-rich hexagonal GeSi nanowire. To this end we will grow
heterostructured GeSi-2H nanowires, control doping (p- & n-type), form junctions and embed
heterostructure quantum dots in Si shell to facilitate conversion of carrier spin into photon polarization

Work Context

Objectives and work plan
The position is available at C2N/departement Matériaux SEEDs team

The PhD student is expected to contribute to :
- in situ TEM observations and video processing
- modelling growth mechanisms
- sample preparation and growth of nanowires on m-plane substrates
- optimisation of growth with axial abrupt heterostructures and control doping
- characterisation of structural and physical properties of the synthesized structures

Additional Information

ONCHIPs project Horizon Europe

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