• Title/Summary/Keyword: CMOS photonics

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SOI CMOS-Based Smart Gas Sensor System for Ubiquitous Sensor Networks

  • Maeng, Sung-Lyul;Guha, Prasanta;Udrea, Florin;Ali, Syed Z.;Santra, Sumita;Gardner, Julian;Park, Jong-Hyurk;Kim, Sang-Hyeob;Moon, Seung-Eon;Park, Kang-Ho;Kim, Jong-Dae;Choi, Young-Jin;Milne, William I.
    • ETRI Journal
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    • v.30 no.4
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    • pp.516-525
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    • 2008
  • This paper proposes a compact, energy-efficient, and smart gas sensor platform technology for ubiquitous sensor network (USN) applications. The compact design of the platform is realized by employing silicon-on-insulator (SOI) technology. The sensing element is fully integrated with SOI CMOS circuits for signal processing and communication. Also, the micro-hotplate operates at high temperatures with extremely low power consumption, which is important for USN applications. ZnO nanowires are synthesized onto the micro-hotplate by a simple hydrothermal process and are patterned by a lift-off to form the gas sensor. The sensor was operated at $200^{\circ}C$ and showed a good response to 100 ppb $NO_2$ gas.

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Performance Comparison of Two Types of Silicon Avalanche Photodetectors Based on N-well/P-substrate and P+/N-well Junctions Fabricated With Standard CMOS Technology

  • Lee, Myung-Jae;Choi, Woo-Young
    • Journal of the Optical Society of Korea
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    • v.15 no.1
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    • pp.1-3
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    • 2011
  • We characterize and analyze silicon avalanche photodetectors (APDs) fabricated with standard complementary metal-oxide-semiconductor (CMOS) technology. Current characteristics, responsivity, avalanche gain, and photodetection bandwidth of CMOS-APDs based on two types of PN junctions, N-well/P-substrate and $P^+$/N-well junctions, are compared and analyzed. It is demonstrated that the CMOS-APD using the $P^+$/N-well junction has higher responsivity as well as higher photodetection bandwidth than N-well/P-substrate. In addition, the important factors influencing CMOS-APD performance are clarified from this investigation.

High-sensitivity NIR Sensing with Stacked Photodiode Architecture

  • Hyunjoon Sung;Yunkyung Kim
    • Current Optics and Photonics
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    • v.7 no.2
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    • pp.200-206
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    • 2023
  • Near-infrared (NIR) sensing technology using CMOS image sensors is used in many applications, including automobiles, biological inspection, surveillance, and mobile devices. An intuitive way to improve NIR sensitivity is to thicken the light absorption layer (silicon). However, thickened silicon lacks NIR sensitivity and has other disadvantages, such as diminished optical performance (e.g. crosstalk) and difficulty in processing. In this paper, a pixel structure for NIR sensing using a stacked CMOS image sensor is introduced. There are two photodetection layers, a conventional layer and a bottom photodiode, in the stacked CMOS image sensor. The bottom photodiode is used as the NIR absorption layer. Therefore, the suggested pixel structure does not change the thickness of the conventional photodiode. To verify the suggested pixel structure, sensitivity was simulated using an optical simulator. As a result, the sensitivity was improved by a maximum of 130% and 160% at wavelengths of 850 nm and 940 nm, respectively, with a pixel size of 1.2 ㎛. Therefore, the proposed pixel structure is useful for NIR sensing without thickening the silicon.

Enhancement of Light Guiding Efficiency in CMOS Image Sensor by Introducing an Optical Thin Film (광학 박막을 채용한 CMOS 이미지 센서 픽셀의 수광 효율)

  • Kang, Myung-Hoon;Ko, Eun-Mi;Lee, Je-Won;Cho, Guan-Sik
    • Korean Journal of Optics and Photonics
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    • v.20 no.1
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    • pp.57-60
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    • 2009
  • We consider introducing an optical thin film to the light guiding wall of a pixel in order to enhance the light guiding efficiency of a CMOS image sensor. Simulating the reflectance as a function of the incidence angle using the Essential Macleod program, we find that the range of total internal reflection is greatly increased for several materials. Particularly when air is chosen as the thin film material, the critical angle of total internal reflection could be shifted to about 50 degrees.

Optical Design of a Modified Catadioptric Omnidirectional Optical System for a Capsule Endoscope to Image Simultaneously Front and Side Views on a RGB/NIR CMOS Sensor (RGB/NIR CMOS 센서에서 정면 영상과 측면 영상을 동시에 결상하는 캡슐 내시경용 개선된 반사굴절식 전방위 광학계의 광학 설계)

  • Hong, Young-Gee;Jo, Jae Heung
    • Korean Journal of Optics and Photonics
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    • v.32 no.6
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    • pp.286-295
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    • 2021
  • A modified catadioptric omnidirectional optical system (MCOOS) using an RGB/NIR CMOS sensor is optically designed for a capsule endoscope with the front field of view (FOV) in visible light (RGB) and side FOV in visible and near-infrared (NIR) light. The front image is captured by the front imaging lens system of the MCOOS, which consists of an additional three lenses arranged behind the secondary mirror of the catadioptric omnidirectional optical system (COOS) and the imaging lens system of the COOS. The side image is properly formed by the COOS. The Nyquist frequencies of the sensor in the RGB and NIR spectra are 90 lp/mm and 180 lp/mm, respectively. The overall length of 12 mm, F-number of 3.5, and two half-angles of front and side half FOV of 70° and 50°-120° of the MCOOS are determined by the design specifications. As a result, a spatial frequency of 154 lp/mm at a modulation transfer function (MTF) of 0.3, a depth of focus (DOF) of -0.051-+0.052 mm, and a cumulative probability of tolerance (CPT) of 99% are obtained from the COOS. Also, the spatial frequency at MTF of 170 lp/mm, DOF of -0.035-0.051 mm, and CPT of 99.9% are attained from the front-imaging lens system of the optimized MCOOS.

A study on the amorphous s-i-n photodiode integrated with CMO IC (CMOS IC와 집적 가능한 비정질 p-i-n 광 수신기 제작에 관한 연구)

  • Kwak, Chol-Ho;Yoo, Hoi-Jun;Jang, Jin;Moon, Byoung-Yeon
    • Korean Journal of Optics and Photonics
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    • v.8 no.6
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    • pp.500-505
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    • 1997
  • Experimental amorphous photodiode is fabricated on CMOS IC using a-Si:H p-i-n structure. Amorphous photodiode is scuccessfully integrated on CMOS IC using amorphous Si produced by PECVD system. The PECVD system can deposit a-Si:H at low temperature so that photodiode can be integrated with CMOS IC structure without any process incompatibility. The fabricated amorphous photodiode has a breakdown voltage of below -20 V, a leakage current of about 1 $\mu\textrm{A}$, and turn-on voltage of 0.6~0.8 V. It is demonstrated that the photocurrent of optical signal can be turned on and off by a small voltage and the fabricated amorphous p-i-n photodiode can be used as an optical switch.

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Surface Emitting Terahertz Transistor Based on Charge Plasma Oscillation

  • Kumar, Mirgender;Park, Si-Hyun
    • Current Optics and Photonics
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    • v.1 no.5
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    • pp.544-550
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    • 2017
  • This simulation based study reports a novel tunable, compact, room temperature terahertz (THz) transistor source, operated on the concept of charge plasma oscillation with the capability of radiating within a terahertz gap. A vertical cavity with a quasi-periodic distributed-Bragg-reflector has been attached to a THz plasma wave transistor to achieve a monochromatic coherent surface emission for single as well as multi-color operation. The resonance frequency has been tuned from 0.5 to 1.5 THz with the variable quality factor of the optical cavity from 5 to 290 and slope efficiency maximized to 11. The proposed surface emitting terahertz transistor is able to satisfy the demand for compact solid state terahertz sources in the field of teratronics. The proposed device can be integrated with Si CMOS technology and has opened the way towards the development of silicon photonics.

The Optical Measurement and Quantitative Analysis of Algesia in Spodoptera litura Larva

  • Chen, Ying-Yun;Chang, Rong-Seng;Tsai, Mi-Yin;Chen, Der-Chin
    • Journal of the Optical Society of Korea
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    • v.19 no.2
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    • pp.169-174
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    • 2015
  • Muscle vibration measurement has long been an unique scientific study, in general, and the direct reaction of animals to feel pain (algesia), either from vascular or muscle contraction, is a complex perceptual experience. Thus this paper proposes a way to measure animal algesia quantitatively, by measuring the changes in muscle vibration due to a pinprick on the surface of the skin of a Spodoptera litura larva. Using the laser optical triangulation measurement principle, along with a CMOS image sensor, linear laser, software analysis, and other tools, we quantify the subtle object point displacement, with a precision of up to $10{\mu}m$, for our chosen Spodoptera litura larva animal model, in which it is not easy to identify the tiny changes in muscle contraction dynamics with the naked eye. We inject different concentrations of formalin reagent (empty needle, 12% formalin, and 37% formalin) to obtain a variety of different muscle vibration frequencies as the experimental results. Because of the high concentrations of reagent applied, we see a high frequency shift of muscle vibration, which can be presented as pain indices, so that the algesia can be quantified.

Covered Microlens Structure for Quad Color Filter Array of CMOS Image Sensor

  • Jae-Hyeok Hwang;Yunkyung Kim
    • Current Optics and Photonics
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    • v.7 no.5
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    • pp.485-495
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    • 2023
  • The pixel size in high-resolution complementary metal-oxide-semiconductor (CMOS) image sensors continues to shrink due to chip size limitations. However, the pixel pitch's miniaturization causes deterioration of optical performance. As one solution, a quad color filter (CF) array with pixel binning has been developed to enhance sensitivity. For high sensitivity, the microlens structure also needs to be optimized as the CF arrays change. In this paper, the covered microlens, which consist of four microlenses covered by one large microlens, are proposed for the quad CF array in the backside illumination pixel structure. To evaluate the optical performance, the suggested microlens structure was simulated from 0.5 ㎛ to 1.0 ㎛ pixels at the center and edge of the sensors. Moreover, all pixel structures were compared with and without in-pixel deep trench isolation (DTI), which works to distribute incident light uniformly into each photodiode. The suggested structure was evaluated with an optical simulation using the finite-difference time-domain method for numerical analysis of the optical characteristics. Compared to the conventional microlens, the suggested microlens show 29.1% and 33.9% maximum enhancement of sensitivity at the center and edge of the sensor, respectively. Therefore, the covered microlens demonstrated the highly sensitive image sensor with a quad CF array.

Trend and Issues of van der Waals 2D Semiconductor Devices (반데르발스 2차원 반도체소자의 응용과 이슈)

  • Im, Seongil
    • Vacuum Magazine
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    • v.5 no.2
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    • pp.18-22
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    • 2018
  • wo dimensional (2D) van der Waals (vdW) nanosheet semiconductors have recently attracted much attention from researchers because of their potentials as active device materials toward future nano-electronics and -optoelectronics. This review mainly focuses on the features and applications of state-of-the-art vdW 2D material devices which use transition metal dichalcogenides, graphene, hexagonal boron nitride (h-BN), and black phosphorous: field effect transistors (FETs), complementary metal oxide semiconductor (CMOS) inverters, Schottky diode, and PN diode. In a closing remark, important remaining issues of 2D vdW devices are also introduced as requests for future electronics and photonics applications.