In quantum-confined semiconductor nanostructures, electrons exhibit distinctive behavior compared with that in bulk solids. This enables the design of materials with tunable chemical, physical, electrical, and optical properties. Zero-dimensional semiconductor quantum dots (QDs) offer strong light absorption and bright narrowband emission across the visible and infrared wavelengths and have been engineered to exhibit optical gain and lasing. These properties are of interest for imaging, solar energy harvesting, displays, and communications. Here, we offer an overview of advances in the synthesis and understanding of QD nanomaterials, with a focus on colloidal QDs, and discuss their prospects in technologies such as displays and lighting, lasers, sensing, electronics, solar energy conversion, photocatalysis, and quantum information.

Semiconductor quantum dots: Technological progress and future challenges

This perspective provides an overview of early developments, current status, and remaining challenges of microLED (μLED) technology, which was first reported in Applied Physics Letters in 2000 [S. X. Jin, J. Li, J. Z. Li, J. Y. Lin and H. X. Jiang, "GaN Microdisk Light Emitting Diodes," Appl. Phys. Lett. 76, 631 (2000)]. Today, microLED is recognized as the ultimate display technology and is one of the fastest-growing technologies in the world as technology giants utilize it on a wide range of products from large flat panel displays and televisions, wearable displays, and virtual reality displays to light sources for the neural interface and optogenetics. It is anticipated that the collective R&D efforts worldwide will bring microLED products not only to the mass consumer electronic markets but also to serve the society on the broadest scale by encompassing sectors in medical/health, energy, transportation, communications, and entertainment.

Development of microLED

Biosynthesis for the preparation of antimicrobial silver nanoparticles (Ag NPs) is a green method without the use of cytotoxic reducing and surfactant agents. Herein, shape-controlled and well-dispersed Ag NPs were biosynthesized using yeast extract as reducing and capping agents. The synthesized Ag NPs exhibited a uniform spherical shape and fine size, with an average size of 13.8 nm. The biomolecules of reductive amino acids, alpha-linolenic acid, and carbohydrates in yeast extract have a significant role in the formation of Ag NPs, which was proved by the Fourier transform infrared spectroscopy analysis. In addition, amino acids on the surface of Ag NPs carry net negative charges which maximize the electrostatic repulsion interactions in alkaline solution, providing favorable stability for more than a year without precipitation. The Ag NPs in combination treatment with ampicillin reversed the resistance in ampicillin-resistant E. coli cells. These monodispersed Ag NPs could be a promising alternative for the disinfection of multidrug-resistant bacterial strains, and they showed negligible cytotoxicity and good biocompatibility toward Cos-7 cells.

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Biosynthesis and Antibacterial Activity of Silver Nanoparticles Using Yeast Extract as Reducing and Capping Agents

Yttrium aluminum garnet (YAG) laser operation has been achieved using a single gallium arsenide laser diode as the pump. Repetition rates of 200 pulses per second have been achieved in initial experiments. Compared to flashlamp pumping, semiconductor laser pumping requires less. than 5 percent of the light energy to accomplish YAG lasing. Extraordinary repeatability of laser output, pulse to pulse, has been obtained.

YAG laser operation by semiconductor laser pumping

Photodetectors built from conventional bulk materials such as silicon, III-V or II-VI compound semiconductors are one of the most ubiquitous types of technology in use today. The past decade has witnessed a dramatic increase in interest in emerging photodetectors based on perovskite materials driven by the growing demands for uncooled, low-cost, lightweight, and even flexible photodetection technology. Though perovskite has good electrical and optical properties, perovskite-based photodetectors always suffer from nonideal quantum efficiency and high-power consumption. Joint manipulation of electrons and photons in perovskite photodetectors is a promising strategy to improve detection efficiency. In this review, electrical and optical characteristics of typical types of perovskite photodetectors are first summarized. Electrical manipulations of electrons in perovskite photodetectors are discussed. Then, artificial photonic nanostructures for photon manipulations are detailed to improve light absorption efficiency. By reviewing the manipulation of electrons and photons in perovskite photodetectors, this review aims to provide strategies to achieve high-performance photodetectors.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.202100569

Recent Progress on Electrical and Optical Manipulations of Perovskite Photodetectors.

This paper presents the performance characteristics of InP-based p-i-n photodiodes with strain-compensated and lattice-matched InGaAs/GaAsSb type-II multiple quantum well (MQW) absorption regions. The results show that photodiodes with strain-compensated and lattice-matched absorption regions have optical response out to 3.4 and 2.8 μm with dark current densities of 9.7 and 1.66 mA cm-2,respectively, at 290 K under -0.5 V reverse bias. The carrier transport mechanism responsible for the difference in responsivity and detectivity between strain-compensated and lattice-matched InGaAs/GaAsSb MQWs is discussed.

SWIR/MWIR InP-Based p-i-n Photodiodes With InGaAs/GaAsSb Type-II Quantum Wells

Current optical communication systems operating at the 1.55 μm wavelength band may not be able to continually satisfy the growing demand on data capacity within the next few years. Opening a new spectral window around the 2 μm wavelength with recently developed hollow-core photonic bandgap fiber and a thulium-doped fiber amplifier is a promising solution to increase transmission capacity due to the low-loss and wide-bandwidth properties of these components at this wavelength band. However, as a key component, the performance of current high-speed photodetectors at the 2 μm wavelength is still not comparable with those at the 1.55 μm wavelength band, which chokes the feasibility of the new spectral window. In this work, we demonstrate, for the first time to our knowledge, a high-speed uni-traveling carrier photodiode for 2 μm applications with InGaAs/GaAsSb type-II multiple quantum wells as the absorption region, which is lattice-matched to InP. The devices have the responsivity of 0.07 A/W at 2 μm wavelength, and the device with a 10 μm diameter shows a 3 dB bandwidth of 25 GHz at −3  V bias voltage. To the best of our knowledge, this device is the fastest photodiode among all group III-V and group IV photodetectors working in the 2 μm wavelength range.

High-speed uni-traveling carrier photodiode for 2 μm wavelength application

An InP-based p-i-n photodiode with optical response out to 3.4 μm was designed and grown by molecular beam epitaxy (MBE). One hundred pairs of 7-nm In0.34Ga0.66As/5-nm GaAs0.25Sb0.75 quantum wells strain compensated to InP were used as the absorption region. The device showed a dark current density of 9.6 mA/cm2 under -0.5-V reverse bias, a responsivity of 0.03 A/W, and a detectivity of 2.0 × 108 cm·Hz1/2·W-1 at 3 μm at 290 K.

Demonstration of a Room-Temperature InP-Based Photodetector Operating Beyond 3 $\mu$ m

In this paper, the transition wavelength and wave function overlap of type-II InxGa1-xAs/GaAs1-ySby quantum wells are numerically calculated using a 4-band k · p Hamiltonian model The simulation results indicate that absorption wavelength from 2 to 4 μm can be achieved with a strain compensated quantum well structure The transition wavelength and wave function overlap can be optimized by properly selecting the thicknesses and composition of the quantum well layers

Design of strain compensated InGaAs/GaAsSb type-II quantum well structures for mid-infrared photodiodes

Avalanche photodiodes (APDs) on Si operating at optical communication wavelength band are crucial for the Si-based transceiver application. In this paper, we report the first O-band InAs quantum dot (QD) waveguide APDs monolithically grown on Si with a low dark current of 0.1 nA at unit gain and a responsivity of 0.234 A/W at 1.310 μm at unit gain (−5 V). In the linear gain mode, the APDs have a maximum gain of 198 and show a clear eye diagram up to 8 Gbit/s. These QD-based APDs enjoy the benefit of sharing the same epitaxial layers and processing flow as QD lasers, which could potentially facilitate the integration with laser sources on a Si platform.

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Baile Chen

Papers

SWIR/MWIR InP-Based p-i-n Photodiodes With InGaAs/GaAsSb Type-II Quantum Wells

High-speed uni-traveling carrier photodiode for 2 μm wavelength application

Demonstration of a Room-Temperature InP-Based Photodetector Operating Beyond 3 $\mu$ m

Design of strain compensated InGaAs/GaAsSb type-II quantum well structures for mid-infrared photodiodes

Low Dark Current High Gain InAs Quantum Dot Avalanche Photodiodes Monolithically Grown on Si