Direct Gap related Optical Properties of Ge/SiGe Multiple Quantum Wells (GOsPEL)
JCJC – SIMI 3 (2011-2014)


Le projet Gospel a reçu le prix de l’impact sociétal de l’ANR lors des rencontres du numériques de l’ANR les 16 et 17 novembre 2016 !


Silicon photonics has generated an increasing interest in the recent years. The integration of optics and electronics on a same chip would allow the enhancement of integrated circuit performances, and optical telecommunications can benefit from the development of low cost and high performance solutions for high-speed optical links. Silicon based-optoelectronic devices are the key building blocks for the development of silicon photonics. Despite the demonstration of high performance silicon modulator, germanium photodetectors, and the achievement of optical sources using III-V material bonded on silicon, the integration of these different elements on an electronic chip is highly challenging due to the different materials and technologies for each building block. In addition, wideband silicon modulators require active regions longer than 1 mm which makes their integration on electronic chips difficult.
The real development of silicon photonics needs to solve these challenging points, and this will be possible only by using innovative breaking concepts. In this context, GOSPEL project propose to study direct gap-related optical properties of Ge/SiGe multiple quantum wells (MQW). Indeed, in 2005, photocurrent spectroscopy has been used to demonstrate that Quantum Confined Stark Effect (QCSE) can be obtained in Ge/SiGe quantum wells (QW), which is an important breakthrough as it was the first demonstration of using direct gap related effect in indirect bandgap materials. This demonstration has paved the way for a lot exciting works related to a good understanding of the mechanisms in these Ge/SiGe QW structures and for the achievement of innovative optoelectronic devices based on these mechanisms.
In this context the goal of GOSPEL project is to study physical, optical and optoelectronic properties of Ge/SiGe multiple quantum wells to go towards photonic devices. The structures are grown by low energy plasma enhanced chemical vapour deposition (LEPECVD), in L-Ness lab (Como – Politecnico di Milano, Italy) thanks to collaboration with Giovanni Isella’s group. Due to the large lattice mismatch between Si and Ge, a graded SiGe buffer is used, with Ge concentration of SiGe layer grown from zero to the final concentration with a continuous change to obtain a relaxed Ge-rich SiGe layer, where high quality Ge/SiGe quantum wells can be grown. Indeed the preliminary results allowed us to demonstrate QCSE at room temperature for light incident perpendicular and for the first time parallel to the QW planes, which is directly related to integrated photonic applications.

In GOSPEL project, material properties (energy and intensity of excitonic peaks, carrier dynamics and transport) and optoelectronic properties (influence of external electric field, luminescence) of Ge/SiGe MQW structures will be compared to theoretical results, in order to improve the understanding of physical properties in these structures. Devices based on these new effects will be designed and fabricated in order to experimentally observe light modulation, detection, and emitting properties of the Ge/SiGe MQW structures. GOSPEL project will then give answers on the possibilities and opportunities to develop a new and innovative Ge/SiGe photonics platform.



Project highlights:

– Demonstration of a compact optical modulator (< 100 µm) with a low power consumption (~100 fJ/bit) : an extinction rate up to 10 dB has been obtained with optical losses of only 5 dB, operating at 20GHz.

– First demonstration of room temperature electroluminescence in Ge/SiGe waveguides

– Demonstration of the possibility to tune the band-edge wavelength and the Quantum Confiend Stark Effect by strain and design enginnering. Operation at the standard wavelength of 1.3 µm has been demonstrated.

First demonstration of eleectrorefraction in Ge/SiGe QW structures, opening the route towards phase modulators, needed for example to modulate optical signals with advanced modulation formats. (QPSK).

– Proposal for a new integration scheme of Ge/SiGe QW structures in silicon photonics circuits and demonstration of an integrated optical link including a modulator, a waveguide and a photodetector on the same silicon photonics circuit



    Articles in Journals

    1. P. Chaisakul, D. Marris-Morini, G. Isella, D. Chrastina, N. Izard, X. Le Roux, S. Edmond, J-R Coudevylle, L. Vivien,
      Room temperature direct gap electroluminescence from Ge/Si0.15Ge0.85 multiple quantum well edge emitting diode
      Applied Physics Letters, 99, 141106, (2011).

    2. P. Chaisakul, D. Marris-Morini, M-S. Rouifed, G. Isella, D. Chrastina, J. Frigerio, X. Le Roux, S. Edmond, J-R. Coudevylle, L. Vivien
      23 GHz Ge/SiGe multiple quantum well electro-absorption modulator
      Optics Express, 20 (3), 3219-3225, (2012)

    3. Rouifed M-S., Chaisakul P., Marris-Morini D., Frigerio J., Isella G., Chrastina D., Edmond S., Le Roux X. , Coudevylle J-R., Vivien L.,
      Quantum-confined Stark effect at 1.3 μm in Ge/Si0.35Ge0.65 quantum-well structure,
      Optics Letters 37, 3960 (2012).

    4. J. Frigerio, P. Chaisakul, D. Marris-Morini, S. Cecchi, M. S Rouifed, G. Isella, L. Vivien,
      Electro-refractive effect in Ge/SiGe multiple quantum wells,
      Applied physics letters 102 , 061102 (2013).

    5. P. Chaisakul, D. Marris-Morini, G. Isella, D. Chrastina, M-S Rouifed, J. Frigerio, L. Vivien
      Ge quantum well optoelectronic devices for light modulation, detection, and emission
      Solid state electronics 83, 92 (2013)

    6. P. Chaisakul, D. Marris-Morini, M. S. Rouifed, J. Frigerio, G. Isella, D. Chrastina, J.-R. Coudevylle, X. Le Roux, S. Edmond, D. Bouville, L. Vivien
      Strong quantum-confined Stark effect from light hole related direct-gap transitions in Ge quantum wells
      Applied Physics Letters 102, 191107 (2013)

    7. D. Marris-Morini, P. Chaisakul, M-S Rouifed, J. Frigerio, D. Chrastina, G. Isella, S. Edmond, X. Le Roux, J-R. Coudevylle, L. Vivien,
      Towards low energy consumption integrated photonic circuits based on Ge/SiGe quantum wells
      DOI: 10.1515/nanoph-2013-0018, (2013),
      Nanophotonics Volume 2, Issue 4, 279-288,
      invited review paper

    8. P. Chaisakul, D. Marris-Morini, M-S Rouifed, J. Frigerio, D. Chrastina, J-R. Coudevylle, X. Le Roux, S. Edmond, G. Isella, L. Vivien,
      Recent progress in GeSi electro-absorption modulators,
      Science and Technology of Advanced Materials, 15, 014601 (2014)
      invited review paper.

    9. M-S. Rouifed, D. Marris-Morini, P. Chaisakul, J. Frigerio, G. Isella, D. Chrastina, S. Edmond, X. Le Roux, J-R. Coudevylle, D. Bouville, L. Vivien,
      Advances Toward Ge/SiGe Quantum-Well Waveguide Modulators at 1.3μm
      DOI : 10.1109/JSTQE.2013.2294456
      IEEE Journal of Selected topics in quantum electronics, 20, 4, 3400207 (2014).

    10. P. Chaisakul, D. Marris-Morini, J. Frigerio, D. Chrastina, M-S Rouifed, S. Cecchi, P. Crozat, G. Isella, and L. Vivien,
      Integrated germanium optical interconnects on silicon substrates,
      Nature Photonics 8, 482-488 (2014)

    11. P. Chaisakul, J. Frigerio, D. Marris-Morini, V. Vakarin, D. Chrastina, G. Isella, and L. Vivien,
      O-band quantum-confined Stark effect optical modulator from Ge/Si0.15Ge0.85 quantum wells by well thickness tuning,
      Journal of Applied Physics, 116 , 193103 (2014)