Kaikai Xu

Compared to the widely used compound semiconductor photoelectric sensors, all-silicon photoelectric sensors have the advantage of easy mass production because they are compatible with the complementary metal-oxide-semiconductor (CMOS) fabrication technique. In this paper, we propose an all-silicon photoelectric biosensor with a simple process and that is integrated, miniature, and with low loss. This biosensor is based on monolithic integration technology, and its light source is a PN junction cascaded polysilicon nanostructure. The detection device utilizes a simple refractive index sensing method. According to our simulation, when the refractive index of the detected material is more than 1.52, evanescent wave intensity decreases with the growth of the refractive index. Thus, refractive index sensing can be achieved. Moreover, it was also shown that, compared to a slab waveguide, the embedded waveguide designed in this paper has a lower loss. With these features, our all-silicon photoelectric biosensor (ASPB) demonstrates its potential in the application of handheld biosensors.

With the explosive growth of human society’s demand for information [1] , microwaves have become a vital information carrier for applications such as wireless communication, military radar, and electronic countermeasures. However, the processing rates and bandwidth of traditional microwave processing circuits are limited, which can create an electronic bottleneck for high-frequency microwave signals. Relying solely on traditional electrical systems has not been enough to meet the emerging demand for high-frequency microwave signal generation, transmission, and processing [2] , [3] . At the same time, broadband and low-loss photonics have led to an ever-increasing interest in generating, processing, controlling, and distributing microwave and millimeter-wave (mm-wave) signals for applications such as broadband wireless access networks, sensor networks, radar, satellite communication, instrumentation, and warfare systems [4] . In response, beginning in the 1990s, these two technologies merged and produced a new interdisciplinary field known as microwave photonics [5] , [6] .

Two-dimensional (2D) selenium was synthesized successfully in 2017. Its advanced properties, including size-dependent bandgap, excellent environmental robustness, strong photoluminescence effect, anisotropic thermal conductivity, and high photoconductivity, render it and selenium-based composites a promising candidate for various device applications. These include batteries, modulators, photodetectors, and photothermal effects in medical applications. However, compared to other commonly used 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorus, 2D Se is much less known. Motivated by the need to overcome this lack of knowledge, this article focuses on recent progress and elucidates the crystal structure, synthesis methods, physical properties, applications, challenges, and prospects of 2D Se nanoflakes.

In this paper, optoelectronic characteristics and related switching behavior of one monolithically integrated silicon light-emitting device (LED) with an interesting wavelength range of 400–900 nm are studied. Through the comparison of two types of geometry, Si avalanche-based LED and Si field-effect LED (Si FE LED), in the same device, we establish the dimensional dependence of the switching speed of the LED. Almost-linear modulation curve implies lower distortion is shown for the Si FE LED with light emission enhancement, and technology computer aided design (TCAD) simulations are in line with the experimental results. Our findings indicate that ON–OFF keying up to GHz frequencies should be feasible with such diodes. Potential applications should include Si FE LED integrated into the micro-photonic systems.

All-CMOS monolithic microdisplay technologies have been attracting attention due to their direct integration of light-emitting pixel arrays and driving circuits on a single silicon substrate. Improvements to optical power efficiency have been a hot spot for all-silicon microdisplay technologies. MOS-like gate-control structure avalanche-mode light-emitting diodes (AMLEDs) that employ hot-carrier electroluminescence to produce light emission are used to enhance the optical power efficiency of pixel units. A semi-active matrix mode is used to reduce the power consumption of driver circuits. A 100×100 pixel array with an all-CMOS monolithic microdisplay system is demonstrated using standard 0.18μm CMOS technology. The optical emission power and the breakdown voltage of the proposed AMLEDs are increased by 139.2% and reduced by more than 67%, respectively. The optical-power efficiency is 5.98×10 ^-7 which is comparable to the best reported so far in all-CMOS monolithic microdisplay chip. With its significant optical-power efficiency, the proposed microdisplay technology has broad application prospects in near-to-eye display and head mounted displays (HMDs).

This paper demonstrates a polycrystalline silicon avalanche mode light-emitting device. The unique N⁺PN⁺PN⁺ cascade structure is designed to enhance light intensity via carrier injection engineering, in which the minority carriers are injected from the forward-biased junction to the light emission junction. Visible light can be observed at the reverse-biased PN junctions when the device operating voltage exceeds 20 V. In particular, the phonon-assisted indirect interband recombination of carriers with excess energy may be the main mechanism of photon emission. A specific junction model is proposed to explain that the light intensity peaks are generated primarily via carrier injection. Comparing the spectral measurements of a single polysilicon N⁺P junction device and the proposed cascade device shows that the strategy of improving the luminous intensity via carrier injection engineering is feasible and effective.

Optical transitions in silicon avalanche mode silcon LEDs were modeled, using the energy band structure, available carrier energy and momentum spreads. Based on previous experimental observations, it was hypothesized that emissions at these wavelengths can be enhanced by using a combination of excitation of carriers in high electric fields and scattering of excited carriers in compensated, high dopant impurity p+n+ environments, optical emissions at 650 and 750-850 nm wavelength emission regimes could be stimulated. A number of p+np+ devices were subsequently designed and realized using a 0.35-micron RF bipolar fabrication process that provided control over both carrier energy and carrier balancing. The optical emission characteristics of the devices was analyzed using an optical fiber lensed probe spectrophotometer and high-resolution optical microscopy. Clear evidence is obtained that 650 nm emissions can be enhanced in nano dimensioned emission spots by using these technologies. The devices operated in the 5-10V and 0.08-10mA regime. External emission intensities of up to 100 nW mu m(2) were observed. Furthermore, using the same modeling, light emission was observed at nano-dimensioned regions emitting in the 750 - 850 nm emission region by placing high dopant impurity regions next to lowly doped high E fleld regions, and relaxing and scattering carriers in these zones. The 750 - 850 nm emissions may find application in both short haul and long haul integrated Si AMLEDs coupled to silicon nitride waveguide structures.

Stimulation of 700 and 900 nm optical emissions in a two junction monolithically integrated circuit silicon avalanche mode Si light emitting device have been achieved, based on some first iteration modelling and realization of first iteration experimental results. Previously only stimulation of 600 nm emission intensities had been realized. The current devices are of micron dimension and were realized using a standard Si integrated circuit design in a 0.35-micron RF design process. Evidence has been obtained that 700 nm and 900 nm in Si AM LEDs occur primarily through direct intra-band exited electron and exited hole relaxation phenomena and short-range phonon assisted inter-band transitions. Indications have been obtained that this occurs when energetic electrons relax in a high impurity density charge scattering environment. The devices operate at 8–10 V, 1 mA–10 mA regimes. Emission intensities of up to 1000 nW·µm⁻² at the point of source have been derived. The developed technologies can find diverse new applications for on-chip electro-optic applications, particularly for coupling optical radiation laterally in silicon nitride-based waveguides in silicon integrated circuitry.

Silicon avalanche light-emitting devices (Si Av LEDs) offer various possibilities for realizing micro- and even nano- optical biosensors directly on chip. The light-emitting devices (LEDs) operate in the wavelength range of about 450-850nm, and their optical power emitted is of the order of a few hundreds of nW/µm². These LEDs could be fabricated in micro- and nano- dimensions by using modern semiconductor fabrication processing technologies through the mainstream of silicon material. Through a series of experiments, the dispersion phenomena in the Si Av LED are observed. Also, its light emission point was proved to locate at about one micron just below the silicon-silicon oxide interface. Subsequently, a micro-fluidic channel sensor was designed by using the dispersion characteristics owned by the Si Av LED. The analytes flowing through a micro-fluidic channel could be studied by their specific transmittance and absorption spectra. Moreover, simulations verify that a novel designed waveguide-based sensor could be fabricated on chip between the Si optical source and the Si P-I-N detector.