Progress in Quantum Electronics最新文献

Improving the energy efficiency of electronics is one of the grand challenges of semiconductor device physics, as global energy consumption by electronics grows in tandem with society’s growing reliance on information technology. Computationally intensive applications such as artificial intelligence further incentivizes the improvement of energy efficiency of electronics. At the corpuscular level of the transistor, the challenge is to reduce the operating voltage of the electronic switch while maintaining a sufficient on/off current ratio for reliable circuit operation. Monolayer graphene is a light material with low elastic modulus for flexure and low adhesion energy, ideal for the development of electromechanical switches with low-voltage operation. Critically, monolayer graphene has an elastic modulus lower than that of any other membrane due to its atomic thinness, which in turn enables deflection with less force than any other membrane. In this article, we review recent progress in the development of low-voltage graphene electromechanical switches. We present a general overview of the motivation for low-voltage switches, thermodynamic limits, and the scaling of on/off current ratio with voltage. A summary of the theory of suspended graphene monolayer switches follows. Simple theoretical models for the scaling of pull-in voltage, actuation energy and adhesion energy with device dimensions are reviewed. Experimental work over the past decade towards the realization of suspended graphene switches in both two-terminal and three-terminal configurations is summarized. Our review concludes with an outlook on the continued development of low-voltage graphene switches.

The paper is a review of gas lasers pumped by runaway electrons preionized diffuse discharge (REP DD). The various conditions under which the discharge occurs are described. It is shown that in the presence of the highly non-uniform electric field strength distribution in a gap filled with dense gases, a stable diffuse discharge is ignited without the use of additional sources of ionizing radiation. This, in turn, is achieved by using discharge gaps, in which at least one of the electrodes has a small radius of curvature (e.g., “point-plane”, “blade-blade” and so on), and high-voltage (10s–100s ​kV) pulses with a (sub)nanosecond rise time. With this method of forming the discharge the runaway electrons can produce X-ray quanta in the gap and, together with them, provide preionization of the laser gas mixture. The dense nonequilibrium low-temperature plasma of this discharge can remain diffuse during the entire excitation time, including single pulse excitation and repetitive mode at the voltage pulse repetition rate up to several kHz. The properties and parameters of REP DD plasma are considered. Experimental and simulated characteristics of stimulated emission of REP DD plasma in various gaseous media are presented.

As a newest family member of the III-nitrides, BN is considered amongst the remaining frontiers in wide energy bandgap semiconductors with potentials for technologically significant applications in deep UV (DUV) optoelectronics, solid-state neutron detectors, electron emitters, single photon emitters, switching/memory devices, and super-capacitors. It was shown that it is possible to produce h-BN epilayers with high hexagonal phase purity, UV transparency, and film stoichiometry by employing nitrogen-rich growth conditions. The quasi-2D nature of h-BN supports unusually strong optical transitions near the band edge and a large exciton binding energy on the order of 0.7 ​eV. Due to the fact that the isotope of B-10 has a large capture cross-section for thermal neutrons, h-BN is an ideal material for the fabrication of solid-state neutron detectors for special nuclear materials detection, well and geothermal logging, and medical imaging applications. Freestanding B-10 enriched h-BN (h-¹⁰BN) epilayers with varying thicknesses up to 200 ​μm have been successfully synthesized by metal organic chemical vapor deposition (MOCVD) as of this writing. By utilizing the conductivity anisotropy nature of h-BN, 1 ​cm² lateral detectors fabricated from 100 ​μm thick h-¹⁰BN epilayers have demonstrated a detection efficiency of 59% for thermal neutrons, which is the highest on record among all solid-state neutron detectors as of today. It was noted that high growth temperatures, long growth times and the use of sapphire substrate tend to incorporate oxygen related impurities into h-¹⁰BN epilayers, which strongly impacted the carrier mobility-lifetime (μτ) products and charge collection efficiencies of h-¹⁰BN neutron detectors. As the h-BN material technology further develops, improved carrier mobilities and μτ products will allow the fabrication of h-BN devices with enhanced performance.

III-V semiconductor materials are the basis of photonic devices due to their unique optical properties. There is an increasing demand for fabricating these devices on unconventional substrates for various applications, such as silicon photonic integrated circuits, flexible optoelectronic devices, and ultralow-profile photonics. However, the III-V semiconductor epitaxy often encounters problems from the lattice, thermal, and polarity mismatches with foreign substrates. In recent years, the epitaxial growth of defect-free group–III–V materials through two-dimensional materials has exploded as an attractive area of research. The nonconventional epitaxy way demonstrates potential advantages over conventional ones, including high quality and freedom of using diverse substrates, making them viable candidates for emerging applications. Herein, we offer a complete review of the recent achievements made in this field. We summarize the growth conditions and mechanisms involved in fabricating these structures through different two-dimensional materials. The unique optical properties of the epitaxy correlating with their growth conditions are discussed, along with their respective applications in optics and nanophotonics, including light-emitting diodes, photodetectors, and solar cells. Finally, we detail the remaining obstacles and challenges to exploit the potential for such practical applications fully.

We present a review of selective area epitaxy and its history in the evolution of semiconductor lasers, with a focus on its application at the nanoscale level in the development of quantum dot and nanopore lasers. Recent applications will be discussed including applications to integrated photonics and quantum photonics, such as patterned single-photon sources.

Selective area epitaxial (SAE) growth of III-V materials and devices by metalorganic chemical vapor deposition is selectively reviewed to illustrate the concepts employed in this technology and its most relevant applications. Special focus on the use of SAE use for photonic integration, heterogeneous integration of materials relevant to photonic integration, and nanostructure integration is made. Throughout, the pioneering work led by Professor James J. Coleman is used to illustrate the value of using selective growth for various applications.

With the advent of the Internet of Things, energy- and bandwidth-related issues are becoming increasingly prominent in the context of supporting the massive connectivity of various smart devices. To this end, we propose that solar cells with the dual functions of energy harvesting and signal acquisition are critical for alleviating energy-related issues and enabling optical wireless communication (OWC) across the satellite–air–ground–ocean (SAGO) boundaries. Moreover, we present the first comprehensive survey on solar cell-based OWC technology. First, the historical evolution of this technology is summarized, from its beginnings to recent advances, to provide the relative merits of a variety of solar cells for simultaneous energy harvesting and OWC in different application scenarios. Second, the performance metrics, circuit design, and architectural design for energy-autonomous solar cell receivers are provided to help understand the basic principles of this technology. Finally, with a view to its future application to SAGO communication networks, we note the challenges and future trends of research related to this technology in terms of channel characterization, light source development, photodetector development, modulation and multiplexing techniques, and network implementations.

Lasers based on erbium ions using ⁴I_11/2 ​→ ​⁴I_13/2 transition can generate laser radiation in the spectral range from 2.7 ​μm to 3 ​μm. Since the strong absorption peak of water is located at 3 ​μm, there has been an effort to develop a suitable laser source for various medical applications, e.g. dentistry, dermatology, urology, or surgery. Laser radiation from this wavelength range can also be used in spectroscopy, as a pumping source for optical parametric oscillators, or for further mid-infrared conversion.

This paper represents an overview of the erbium-doped active media (e.g. Er:YAG, Er:YAP, Er:GGG, Er:SrF₂, Er:YLF, Er:Y₂O₃, Er:KYW, etc.) for laser radiation generation in the spectral range 2.7–3 ​μm. In the first part of this paper, the particular active media are discussed in detail. On the other hand, the experimental results summarized absorption and emission cross-section spectra together with decay times at upper (⁴I_11/2) and lower (⁴I_13/2) laser levels of all tested Er-doped samples at room temperature. Moreover, laser results in CW and pulsed laser regime with tunability curves, achieved in recent years, are presented, too.