PhD - Leuven | More than two weeks ago
Apply a unique monolithic III-V integration approach to different III-V alloys with the aim of realizing new hetero-structures for optoelectronic devices in Silicon Photonics
Nano-Ridge Engineering (NRE)  is a unique monolithic integration approach for III-V devices on Si substrates introduced by imec and Ghent University. This hetero-epitaxial concept is based on selective area growth by metal organic vapor phase epitaxy (MOVPE). The monolithic integration starts with the III-V deposition inside narrow and deep trenches, which were fabricated on Si substrates. The epitaxial growth inside these high aspect ratio trenches leads to an efficient trapping of misfit defects, which are caused by the lattice mismatch between III-V materials and Si, and thus, to an improved III-V crystal quality. Once the trenches are filled, the crystal growth is continued out of the trench and the nano-ridge shape as well as volume can be manipulated by the applied MOVPE growth conditions. The figure below shows how the nano-ridge shape can be engineered by changing the growth parameters. NRE was successfully demonstrated for GaAs, GaSb and InGaAs . First optoelectronic devices, such as lasers and photodetectors , were already demonstrated emphasizing the large potential of this exclusive monolithic integration concept.
So far, NRE was only investigated for a few III-V material systems, hence, the topic of this PhD project is the development of new NRE based hetero-structures exploring different III-V alloys, e.g., GaAsSb, GaPSb, InGaAsSb, with a clear focus towards new optoelectronic devices particularly for the infrared wavelength regime.
This experimental research activity includes the design and execution of MOVPE growth experiments, structural as well as optical characterization of the deposited samples and basic simulations to interpretate the results as well as to design new hetero-layer stacks for optoelectronic applications.
As a PhD researcher, you will be co-responsible for your own deposition tool to gain full insight into MOVPE, which is absolutely necessary to establish NRE with new III-V alloys. Your growing understanding of defect formation, based on a systematic correlation between the applied growth conditions and the properties of the samples, obtained via electron channelling contrast imaging, X-ray diffractometry and luminescence measurements will be key to realize nano-ridges with a high crystal quality. Your progress in understanding NRE exploring different III-V materials will decide what kind of hetero-structure should be further optimized towards new optoelectronic devices, and emission/absorption wavelengths. Your regular interaction with other Silicon Photonic research groups at imec and Ghent University will ensure that your new device concepts meet a clear application.
The epitaxial growth and structural characterization will be done at imec whereas the investigation of the optical properties and potential first device fabrication will be carried out at Ghent University.
 B. Kunert, R. Langer, M. Pantouvaki, J. Van Campenhout, and D. Van Thourhout, “Gaining an edge with nano-ridges,” Compd. Semiconcutor, vol. 24, no. 05, pp. 36–41, 2018.
 D. Van Thourhout et al., “Nano-ridge laser monolithically grown on (001) Si,” in Semiconductors and Semimetals, Future Directions in Silicon Photonics, vol. 101, 2019, pp. 283–304.
 M. Baryshnikova et al., “Nano-Ridge Engineering of GaSb for the Integration of InAs/GaSb Heterostructures on 300 mm (001) Si,” Crystals, vol. 10, no. 4, p. 330, 2020.
 B. Kunert et al., “Application of an Sb Surfactant in InGaAs Nano-ridge Engineering on 300 mm Silicon Substrates,” Cryst. Growth Des., vol. 21, no. 3, pp. 1657–1665, 2021.
 Y. Shi et al., “Loss-coupled DFB nano-ridge laser monolithically grown on a standard 300-mm Si wafer,” Opt. Express, vol. Part F140-, no. 10, pp. 14649–14657, 2019.
 C. I. Ozdemir et al., “Low Dark Current and High Responsivity 1020nm InGaAs/GaAs Nano-Ridge Waveguide Photodetector Monolithically Integrated on a 300-mm Si Wafer,” J. Light. Technol., vol. 39, no. 16, pp. 5263–5269, 2021.
Required background: Physics, material science and engineering or chemical engineering. Willingness to work hands-on with an gas phase deposition tool and in a cross-functional team.
Type of work: 30% sample growth, 50% optical and structural characterization, 10% simulation, 10% literature
Supervisor: Dries Van Thourhout
Co-supervisor: Bernardette Kunert
Daily advisor: Yves Mols
The reference code for this position is 2022-039. Mention this reference code on your application form.