Light emission in crystalline silicon is the fundamental goal for the development of an all-silicon device showing efficient infrared emission at room temperature. The exploitation of optically active structural defects that generates sub-bandgap luminescence is the strategy explored here to make silicon an efficient infrared emitter around 1.5 μm.

1. Room temperature μ-PL
Room-temperature emission at telecom wavelengths from
silicon photonic crystal nanocavities
R. Lo Savio, S. L. Portalupi, D. Gerace, L. C. Andreani, M. Galli
Dipartimento di Fisica "A. Volta", Università di Pavia, 27100 Pavia, Italy
A. Shakoor, T. F. Krauss, L. O'Faolain
School of Physics and Astronomy, University of St. Andrews, Fife KY16 9SS, United Kingdom
Perfect agreement between
calculation and experiment
Light emission in crystalline silicon is the fundamental goal for the development of an all-silicon device showing efficient infrared emission at
room temperature that would entail enormous benefits for the realization of on-chip integrated photonic devices. The exploitation of optically
active structural defects that generates sub-bandgap luminescence is one of the strategies explored to make silicon an efficient infrared emitter around 1.5 μm.
Motivation
Far-field optimized L3 PhC nanocavities
PhC parameters: a = 420 nm, r/a = 0.29
Tool for broadband spectroscopic
characterization of Si PhC nanocavities
Conclusions
T-dependence
 Same EA for both on- and off-resonance PL.
Unexpected room-T PL in all-Si L3 PhC cavities at telecom wavelengths
Broadband PL emission (1.3 – 1.6 μm range) in SOI, due to
unintentional defects created during manufacturing process;
Quick and easy tools for spectroscopic characterization;
Purcell enhancement, estimated FP ≈ 10 – 12;
Persistance of on-resonance PL at room temperature.
Far-field patterns
Δr = -18 nm
(far-field optimized cavity)
Δr = 0 nm
(unmodified cavity)
 Unexpected PL emission
 Sharp and intense PL peaks
 PL is enhanced in far-field
optimized cavities
Fundamental cavity modes
Akahane et al., Nature 425, 944 (2003)
Tran et al., Phys. Rev. B 79, 041101(R) (2009)
Portalupi et al., Opt. Expr. 18, 16064 (2010)
Calculated
band structure
Purcell factor estimation
ηM  Calculated from setup geometry
ηC  Calculated from FDTD simulations
α  Measured from μ-PL spectra
Among the highest FP values ever
reported for a PhC nanocavity at
room temperature!
α≈300
α≈60
α≈250
Strong PL enhancement (α)
Extraction efficiency (ηC/ηM)
Purcell effect (FP)
Origin of PL emission
from Si PhC
nanocavities
Optically active defects
unintetionally created by
H+ implantation during
SOI fabrication process
Δr ηC/ηM α
-18 nm 22 250
0 nm 6 60
+18 nm 25 300
Onset of
nonradiative
processes
70°
0°
 Weaker thermal quenching of on-resonance PL.
Yellow holes radii modified
by Δr = ±18 nm
far-field coupling
optimization
 All-Si PhC cavities
 No optically active
internal sources
Electric field profile is higher at normal emission Fundamental for EMITTING
PHOTONIC NANOSTRUCTURES, in
which high Q-factors and good in-
and out-coupling efficiencies are
simultaneously required.
 Q-factor decrease
 RS efficiency (i.e.
vertical coupling)
increase
Persistance of on-resonance PL at
room-T implies an higher radiative
decay rate of on-resonance PL
Strong coupling in the vertical direction
Hauke et al., New J. Phys. 12, 05305 (2010)
Another evidence of
Purcell effect
 Broadband PL in Si-
membrane (on SOI);
 No PL emission in
reference Cz-Si.
‘’Room-temperature emission at telecom wavelengths from silicon
photonic crystal nanocavities’’, Applied Physics Letters 98, 201106 (2011)
ΓRAD  Radiative decay rate
ΓnonRAD  Non-radiative decay rate
T > 100 K Arrhenius plot
Three level model
Δr = +18 nm
cavity