BEGIN:VCALENDAR
VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:69d1ef604f3ca
DTSTART:20230123T090000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:ICFO Auditorium and Online (Teams)
SUMMARY:ICFO | HITESH AGARWAL
CLASS:PUBLIC
DESCRIPTION:Despite the extensive research in the semiconductor industry\, 
 Moore&rsquo\;s law is finally slowing down due to increased complexity. He
 nce\, intense efforts are being carried out to explore hybrid solutions by
  adding additional functionalities to the existing silicon plat- form to k
 eep up with the growing demand. It is colloquially called as &rsquo\;Beyon
 d Moore&rsquo\; phase. This thesis is a humble attempt to propose graphene
 \, a single atomic sheet of carbon\, as an excellent candidate for the &rs
 quo\;Beyond Moore&rsquo\; phase optoelectronic applications. In particular
 \, we demonstrate graphene-based optical interconnects: photodetectors and
  modulators for data communication applications and broadband infrared sen
 sors for hyperspectral space astronomy.\nGraphene has the highest room tem
 perature mobility known to us\, is complementary metal-oxide semiconductor
  (CMOS) compatible\, and has rich electronic and optoelectronic properties
 . In the first part of this thesis\, we used graphene as an active element
  with a passive silicon waveguide platform to demonstrate electro-absorpti
 on modulators and photodetectors. We developed a novel dielectric combinat
 ion by integrating 2D material with 3D oxides\, which enabled us to build 
 a high-quality clean interface with graphene and high-&kappa\; properties.
  This helped us to overcome fundamental limitations and demonstrate a high
  modulation efficiency (&sim\; 2.2 dB/V) and high speed (39 GHz) in the sa
 me device\, surpassing other CMOS-based modulators. In the case of the pho
 todetector\, we demonstrated a photo thermoelectric effect (PTE) based det
 ector with high responsivity (55 mA/W) and a set up limited bandwidth of 4
 0 GHz.\nIn the second part of the thesis\, we address the perpetual issue 
 of limited light absorption in graphene by demonstrating the first 3D phot
 oconductor based on decoupled bilayer graphene layers with 2D-like propert
 ies. Due to the asymmetric environment experienced by our decoupled bilaye
 r graphene layers\, they perceive a strong internal crystal field\, which 
 results in an intrinsic bandgap opening. We exploited this bandgap to obse
 rve a giant photoconductive photoresponse in a broad wavelength range from
  2 to 150 &mu\;m. This is the first reported alternative to slow and expen
 sive thermal detectors for broadband operation and could be instrumental f
 or hyperspectral imaging and infrared astronomy\, bringing us one step clo
 ser to unveiling the secrets of the universe. Finally\, we reported a stro
 ng photoresponse in the out-of-equilibrium criticality state in graphene s
 uperlattices at high bias. We found that the criticality state shifts with
  a change in temperature or light\, resulting in a photoresponse\, imperso
 nating transition-edge behaviour\, which can be potentially interesting fo
 r THz single-photon detection in future.\n&nbsp\;\nThesis Director: Prof D
 r. Frank Koppens
DTSTAMP:20260405T051304Z
END:VEVENT
END:VCALENDAR