25 Gbps low-voltage hetero-structured silicon-
germanium waveguide pin photodetectors for
monolithic on-chip nanophotonic architectures
DANIEL BENEDIKOVIC,
1,
*LÉOPOLD VIROT,
2
GUY AUBIN,
1
FARAH AMAR,
1
BERTRAND SZELAG,
2
BAYRAM KARAKUS,
2
JEAN-MICHEL HARTMANN,
2
CARLOS ALONSO-RAMOS,
1
XAVIER LE ROUX,
1
PAUL CROZAT,
1
ERIC CASSAN,
1
DELPHINE MARRIS-MORINI,
1
CHARLES BAUDOT,
3
FRÉDÉRIC BOEUF,
3
JEAN-MARC FÉDÉLI,
2
CHRISTOPHE KOPP,
2
AND LAURENT VIVIEN
1
1
Centre de Nanosciences et de Nanotechnologies, CNRS, University of Paris-Sud, Université Paris-Saclay, C2N–Palaiseau,
91120 Palaiseau, France
2
University Grenoble Alpes and CEA, LETI, Minatec Campus, F-38054 Grenoble, Grenoble Cedex, France
3
Technology R&D, STMicroelectronics SAS, 850 rue Jean Monnet–38920 Crolles, France
*Corresponding author: daniel.benedikovic@c2n.upsaclay.fr
Received 30 November 2018; revised 24 January 2019; accepted 31 January 2019; posted 6 February 2019 (Doc. ID 353308);
published 15 March 2019
Near-infrared germanium (Ge) photodetectors monolithically integrated on top of silicon-on-insulator substrates
are universally regarded as key enablers towards chip-scale nanop hotonics, with applications ranging from sensing
and health monitoring to object recognition and optical communications. In this work, we report on the high-
data-rate performance pin waveguide photodetectors made of a lateral hetero-structured silicon-Ge-silicon
(Si-Ge-Si) junction operating under low reverse bias at 1.55 μm. The pin photodetector integration scheme con-
siderably eases device manufacturing and is fully compatible with complementary metal-oxide-semiconductor
technology. In particular, the hetero-structured Si-Ge-Si photodetectors show efficiency-b andwidth products of
∼9GHzat −1Vand ∼30 GHz at −3V, with a leakage dark current as low as ∼150 nA, allowing superior signal
detection of high-speed data traffic. A bit-error rate of 10
−9
is achieved for conventional 10 Gbps, 20 Gbps, and
25 Gbps data rates, yielding optical power sensitivities of −13.85 dBm, −12.70 dBm, and − 11.25 dBm, respec-
tively. This demonstration opens up new horizons towards cost-effective Ge pin waveguide photodetectors that
combine fast device operation at low voltages with standard semiconductor fabrication processes, as desired for
reliable on-chip architectures in next-generation nanophotonics integrated circuits.
© 2019 Chinese Laser Press
https://doi.org/10.1364/PRJ.7.000437
1. INTRODUCTION
In order to meet the in creasing demands of an information-
driven society, various levels of communication systems call
upon components able to handle dense data streams. Indeed,
recently adopted copper-based interconnects, with their
inferior electronic and thermal properties, cannot fully satisfy
future data traffic requirements of cloud and data center indus-
tries in terms of bandwidth, speed, energy consumption, and
cost [1–5].
Silicon nanophotonics, notably on silicon-on-insulator
(SOI) substrates [5–8], has emerged as a promising platform
to overcome deficient data traffic flows in on-chip intercon-
nects [9–11]. In this field, optical photodetectors integrated
on an accessible SOI technology are inevitable for myriad
applications ranging from optical communications, sensing, or
health monitoring to object recognition. However, silicon (Si),
an indirect band-gap semiconductor with a cutoff wav elength
of ∼1.1 μm, is not a reliable material for photodetection at
near-infrared (near-IR) wavelengths, i.e., the 1.3–1.55 μm
spectral range historically harnessed by optical communication
windows of low fiber attenuation and dispersion. To address
this deficiency, rather expens ive III–V compound semiconduc-
tors integrated on SOI wafers via flip-chip bonding or direct
heteroexpitaxy can be used [11–13]. However, such integration
typically comes with added fabrication complexity and possibly
some contamination of the Si complementary metal-oxide-
semiconductor (CMOS) pilot lines.
As an alternative, ge rmanium (Ge) has appeared as a prime
choice for near-IR light detection [14–34]. Ge’s appeal comes
from high optical absorption, good crystalline quality, and most
importantly, a low-cost integration scheme that leverages proc-
esses and tools of Si CMOS foundries. Good quality Ge-based
Research Art icle
Vol. 7, No. 4 / April 2019 / Photonics Research 437
2327-9125/19/040437-08 Journal © 2019 Chinese Laser Press