A Programmable Ambient Light Sensor with Dark Current Compensation and Wide Dynamic Range.

Ambient light sensors are becoming increasingly popular due to their effectiveness in extending the battery life of portable electronic devices. However, conventional ambient light sensors are large in area and small in dynamic range, and they do not take into account the effects caused due to a dark current. To address the above problems, a programmable ambient light sensor with dark current compensation and a wide dynamic range is proposed in this paper. The proposed ambient light sensor exhibits a low current power consumption of only 7.7 µA in dark environments, and it operates across a wide voltage range (2-5 V) and temperature range (-40-80 °C). It senses ambient light and provides an output current proportional to the ambient light intensity, with built-in dark current compensation to effectively suppress the effects of a dark current. It provides a wide dynamic range over the entire operating temperature range with three selectable output-current gain modes. The proposed ambient light sensor was designed and fabricated using a 0.18 µm standard CMOS process, and the effective area of the chip is 663 µm × 652 µm. The effectiveness of the circuit was verified through testing, making it highly suitable for portable electronic products and fluorescent fiber-optic temperature sensors.

Blue-light-enhanced avalanche photodiode with a multi-finger grating structure for fluorescence detection.

The responsiveness of the photodetectors is critical to the accuracy of the fluorescent fiber optical temperature sensor. However, the current gain and signal-to-noise ratio (SNR) of traditional photodiodes (PDs) is low, which makes it difficult to meet the high-precision detection requirements of the system. In response to the above problems, this paper achieves a novel, to the best of our knowledge, multi-finger grating (MFG) avalanche photodiode (APD). The device combines the polysilicon gate and the space charge region formed by P+/N-Well to detect photon signals. The conversion capability of the photodetector can be significantly enhanced by the MFG structure. The principle of the device is simulated and verified by technology-computer-aided design (TCAD). The standard grating APD (SG-APD), 2-finger grating APD (2FG-APD), 3-finger grating APD (3FG-APD), and 4-finger grating APD (4FG-APD) are fabricated based on 0.18 µm CMOS process. The optoelectronic detection characteristics of these devices are analyzed by establishing an optoelectronic test platform. At 480 nm, the responsivity of 2FG-APD, 3FG-APD, and 4FG-APD increases by 79.3%, 96.9%, and 70.2%, respectively, compared to SG-APD (4.021 A/W). The test results indicate that 3FG-APD exhibits a strong photon response in the blue light range. The device has broad application prospects in the field of fluorescence detection.

Gate-controlled silicon controlled rectifier with adjustable clamping voltage using a photoelectric mechanism.

In order to flexibly control the voltage-clamping capability of silicon controlled rectifiers (SCRs), this paper proposes a photoelectric gate-controlled SCR (PGCSCR). Equivalent circuits and technology computer aided design (TCAD) simulations are used to analyze how the device works. The device has been validated by a standard 0.18 µm Bipolar CMOS DMOS (BCD) process. The ES620-50 Transmission Line Pulse (TLP) test system was used to verify the impact of the photoelectric effect on the electro-static discharge (ESD) characteristics of the device. The test result shows that the clamping voltage at the holding point of the PGCSCR under the light-free condition is 4.308 V. When the optical power is 5 W/µm2 and the 450 nm wavelength spot is irradiated on the surface of the device, the clamping voltage at the holding point of the PGCSCR is reduced to 3.655 V. And by changing the wavelength of the incident light spot (600 nm), the clamping voltage (3.409 V) of the device changes. Finally, based on the avalanche multiplication effect and the photoelectric effect, the change in the clamping voltage of the device can be further explained. PGCSCR can flexibly adjust the clamping voltage of the device according to the ESD window requirements of the target chip without changing the structure and size, and is expected to be applied in the fields of integrated optical circuits, opto-coupling, and optical communication.

Characteristic analysis of volatile avalanche diode threshold switching for bionic nerve synapse applications.

The combination of biological neurology and memristive theory has greatly promoted the development of neuromorphic computing. To build a large-scale artificial intelligence alert system, the exploration of bionic synapses compatible with standard processes has become an urgent problem to be solved in the next step. In response to the above application requirements, this paper proposes a volatile avalanche diode threshold switching (VADTS) that is fully compatible with standard semiconductor technology to simulate the various functions of the synapse. Technology computer-aided design device-level simulation can verify the bionic principle of VADTS. The function of VADTS's bionic synapse was verified by the experimental test platform. The results show that under the action of the excitation signal (11.25 V), the device can continuously change from a high-resistance state to a low-resistance state. When the excitation signal is lower than the threshold, VADTS presents a "no adaptation" state of nerve synapses. When the excitation signal is higher than the threshold and changes continuously, the current changes along with the amplitude of the excitation signal, similar to the "sensitization" state of the nerve synapse.

High-Sensitivity Terahertz Refractive Index Sensor in a Multilayered Structure with Graphene.

In this paper, we propose a high-sensitivity optical sensor at terahertz frequencies based on a composite structure containing a one-dimensional photonic crystal (1D PC) coated with a layer of monolayer graphene. Between the 1D PC and the graphene there is a sensing medium. This high-sensitivity phenomenon originates from the excitation of optical resonance between the graphene and the 1D PC. The proposed sensor is highly sensitive to the Fermi energy of graphene, the thickness and refractive index of the sensing medium, and the number of graphene layers. By selecting appropriate parameters, the maximum sensitivity ( ) is obtained. We believe the proposed configuration is promising for fabricating graphene-based biosensor- or gas-sensor devices and other related applications in the terahertz band.