The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ∼ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

Lasing is experimentally demonstrated in a direct bandgap GeSn alloy, grown directly onto Si(001). The authors observe a clear lasing threshold as well as linewidth narrowing at low temperatures.

/pdf/lasing-in-direct-bandgap-gesn-alloy-grown-on-si-515b98x7i8.pdf

Lasing in direct-bandgap GeSn alloy grown on Si

Near-infrared (NIR) solid-state micro/nanolasers are important building blocks for true integration of optoelectronic circuitry.1 Although significant progress has been made in III–V nanowire lasers with achieving NIR lasing at room temperature,2−4 challenges remain including low quantum efficiencies and high Auger losses. Importantly, the obstacles toward integrating one-dimensional nanowires on the planar ubiquitous Si platform need to be effectively tackled. Here we demonstrate a new family of planar room-temperature NIR nanolasers based on organic–inorganic perovskite CH3NH3PbI3-aXa (X = I, Br, Cl) nanoplatelets. Their large exciton binding energies, long diffusion lengths, and naturally formed high-quality planar whispering-gallery mode cavities ensure adequate gain and efficient optical feedback for low-threshold optically pumped in-plane lasing. We show that these remarkable wavelength tunable whispering-gallery nanolasers can be easily integrated onto conductive platforms (Si, Au, indium tin oxide...

Room-temperature near-infrared high-Q perovskite whispering-gallery planar nanolasers.

Optical communications and computing require on-chip nonreciprocal light propagation to isolate and stabilize different chip-scale optical components. We have designed and fabricated a metallic-silicon waveguide system in which the optical potential is modulated along the length of the waveguide such that nonreciprocal light propagation is obtained on a silicon photonic chip. Nonreciprocal light transport and one-way photonic mode conversion are demonstrated at the wavelength of 1.55 micrometers in both simulations and experiments. Our system is compatible with conventional complementary metal-oxide-semiconductor processing, providing a way to chip-scale optical isolators for optical communications and computing.

http://science.sciencemag.org/content/sci/333/6043/729.full.pdf

Nonreciprocal Light Propagation in a Silicon Photonic Circuit

Near-infrared lasers are important for optical data communication, spectroscopy and medical diagnosis. Semiconductor nanowires offer the possibility of reducing the footprint of devices for three-dimensional device integration and hence are being extensively studied in the context of optoelectronic devices1, 2. Although visible and ultraviolet nanowire lasers have been demonstrated widely3, 4, 5, 6, 7, 8, 9, 10, 11, progress towards room-temperature infrared nanowire lasers has been limited because of material quality issues and Auger recombination12, 13. (Al)GaAs is an important material system for infrared lasers that is extensively used for conventional lasers. GaAs has a very large surface recombination velocity, which is a serious issue for nanowire devices because of their large surface-to-volume ratio14, 15. Here, we demonstrate room-temperature lasing in core–shell–cap GaAs/AlGaAs/GaAs nanowires by properly designing the Fabry–Perot cavity, optimizing the material quality and minimizing surface recombination. Our demonstration is a major step towards incorporating (Al)GaAs nanowire lasers into the design of nanoscale optoelectronic devices operating at near-infrared wavelengths.

Optically pumped room-temperature GaAs nanowire lasers

Based on a CMOS-compatible growth process, researchers successfully demonstrate the bottom-up integration of InGaAs nanopillar lasers onto silicon chips. The resulting nanolaser offers tiny footprints and scalability, making it particularly suited to high-density optoelectronics.

Nanolasers grown on silicon

We report the use of highly ordered, dense, and regular arrays of in-plane GaAs nanowires as building blocks to produce antiphase-domain-free GaAs thin films on exact (001) silicon. High quality GaAs nanowires were grown on V-grooved Si (001) substrates using the selective aspect ratio trapping concept. The 4.1% lattice mismatch has been accommodated by the initial GaAs, a few nanometer-thick with high density stacking faults. The bulk of the GaAs wires exhibited smooth facets and a low defect density. An unusual defect trapping mechanism by a “tiara”-like structure formed by Si undercuts was discovered. As a result, we were able to grow large-area antiphase-domain-free GaAs thin films out of the nanowires without using SiO2 sidewalls for defect termination. Analysis from XRD ω-rocking curves yielded full-width-at-half-maximum values of 238 and 154 arc sec from 900 to 2000 nm GaAs thin films, respectively, indicating high crystalline quality. The growth scheme in this work offers a promising path towards ...

/pdf/growing-antiphase-domain-free-gaas-thin-films-out-of-highly-176sfgo7bq.pdf

Growing antiphase-domain-free GaAs thin films out of highly ordered planar nanowire arrays on exact (001) silicon

Monolithic integration of III−V compound semiconductor devices with silicon CMOS integrated circuits has been hindered by large lattice mismatches and incompatible processing due to high III−V epitaxy temperatures. We report the first GaAs-based avalanche photodiodes (APDs) and light emitting diodes, directly grown on silicon at a very low, CMOS-compatible temperature and fabricated using conventional microfabrication techniques. The APDs exhibit an extraordinarily large multiplication factor at low voltage resulting from the unique needle shape and growth mode.

GaAs-Based Nanoneedle Light Emitting Diode and Avalanche Photodiode Monolithically Integrated on a Silicon Substrate

High performance NiO/ $\beta $ -Ga2O3 heterojunction pn diodes were realized by applying a sputtered p-type NiO film onto a lightly doped n-type $\beta $ -Ga2O3 epitaxial layer. Taking advantage of the high barrier height against carriers within the pn heterojunction, the demonstrated device exhibited a high breakdown voltage ( ${V}_{B}{)}$ of 1059 V without optimized electric field management techniques, and before breakdown the reverse leakage current density remained below $1~\mu \text{A}$ /cm2. Simultaneously, a relatively low specific on-resistance ( $R_{\text {on, sp}}{)}$ of 3.5 $\text{m}\Omega \cdot \text {cm}^{{2}}$ was achieved. The built-in potential of the heterojunction that determined by a capacitance-voltage ( ${C}$ - ${V}$ ) measurement was around 2.4 eV. As discussed in terms of the energy band diagram of a type-II heterojunction, the conduction band and valence band offsets at the NiO/ $\beta $ -Ga2O3 hetero-interface were estimated to be 1.2 and 2.3 eV, respectively.

1-kV Sputtered p-NiO/n-Ga 2 O 3 Heterojunction Diodes With an Ultra-Low Leakage Current Below $1~\mu$ A/cm 2

The integration of photonic components on silicon chips creates the challenge of achieving a uniform and efficient architecture. Here, the authors demonstrate on-chip light-emitters, photodetectors, photovoltaic power supply and optical data link, all based on InGaAs nanoresonators grown on silicon.

/pdf/nanophotonic-integrated-circuits-from-nanoresonators-grown-5cotoq22cv.pdf

Kar Wei Ng

Papers

Nanolasers grown on silicon

Growing antiphase-domain-free GaAs thin films out of highly ordered planar nanowire arrays on exact (001) silicon

GaAs-Based Nanoneedle Light Emitting Diode and Avalanche Photodiode Monolithically Integrated on a Silicon Substrate

1-kV Sputtered p-NiO/n-Ga 2 O 3 Heterojunction Diodes With an Ultra-Low Leakage Current Below $1~\mu$ A/cm 2

Nanophotonic integrated circuits from nanoresonators grown on silicon