Boelter Chair Seminar
10 A.M. (PDT) Wednesday, August 10, 2022
In-person Engineering IV, Room 54-134 (Shannon Room)
Or
Zoom Link
Heteroepitaxy Brings Light To Silicon: Recent Advances Towards A
Si-based Quantum Cascade Laser
Dr. Giovanni Capellini
Full Professor of Experimental Condensed Matter Physics
University of Roma Tre, Italy
Abstract: Nowadays, the field of semiconductor science is seeing an ever-growing intertwining between fundamental
research and applications, which shortens the distance between discoveries in academic laboratories and the creation of
new devices. A clear example is the exploitation of quantum effects in nanoscale devices to improve performances and
add functionalities while reducing their size. In particular, there is steady interest for Ge/Si heterostructures driven by
their peculiar electrical and optical properties and by their compatibility with the Si-based CMOS manufacturing, inspiring
a plethora of novel devices and systems, which could be potentially manufactured at a low cost. Recently, a subset of the
Ge/Si material system, i.e. the high Ge content SiGe/Ge heterostructures, has been in the spotlight for different
applications, ranging from photonics, to quantum computing, and microelectronics. However, their deposition on
technology–relevant silicon substrates presents several challenges, mainly due to the large mismatch of lattice parameters
and of the thermal expansion coefficients between the Ge-rich structures and the substrate. Therefore, it is mandatory to
achieve the highest degree of control over the heteroepitaxial process to enabling any technology based on this material
system. In this work, I discuss the hurdles inherent to the realization of probably one of the most difficult device to achieve:
a Si-based quantum cascade laser (QCL) operating in the THz spectral region. Indeed, the active region of this device must
comprise of a multi-µm thick stack of hundreds of strain-balanced Ge/SiGe quantum wells, whose thickness and
composition must be controlled at the sub-nanometer level. This device could have a significant impact on the long-sought
quest to develop compact, low cost, and powerful sources operating at room temperature (RT) in the entire far-infrared
range of the electromagnetic spectrum, thus enabling a fully integrated THz platform that can be used in e.g. molecular
sensing and beyond 6G telecommunication.
Bio: Giovanni Capellini is a Full Professor in Experimental Condensed Matter Physics at the "Roma Tre" University (Italy)
and Scientist at the Leibniz-Institut Innovations for High Performance Microelectronics (Frankfurt Oder, Germany). He
obtained his M.Sc. in Physics from "La Sapienza" University (1994, Roma, Italy) and his Ph.D. in Condensed Matter Physics
from "Tor Vergata" University (1998, Roma, Ita). He has been Visiting Associate Professor at the California Institute of
Technology (Pasadena, Ca, USA) and senior scientist at Luxtera Inc., developing the silicon nano-photonic platform
(Carlsbad, Ca, USA). He has been Senior Visiting Academic at the Atomic Fabrication Facility of the University of New South
Wales (Sydney, Australia). His main field of interest is the development of innovative materials and devices in the realm
of silicon-based nano-photonics and nano-electronics and bio-sensing systems, with special focus on heterostructures of
elemental semiconductors. He coauthored more than 200 peer-reviewed articles and international patents.