Light-Controlled Gap-Type TFT Used for Large-Area Under-Screen Fingerprint Sensor

Tai, Ya‐Hsiang; Tu, Cheng-Che; Yuan, Yi‐Cheng; Chang, Yujia; Hsu, Mao-Hsiu; Chuang, Che-Yu

doi:10.1109/jeds.2021.3076832

Cited by 15 publications

(13 citation statements)

References 11 publications

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“…Our prototype is equivalent to 75 magnification of the actual display and fingerprint. In an actual display scale, various fingerprint recognition technologies using additional photodetectors have been studied [21][22][23]. The photodetection according to the reflectance of the fingerprint in the micrometer scale has been clearly verified.…”

Section: Resultsmentioning

confidence: 99%

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

et al. 2022

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This paper proposes a new architecture for a micro light emitting diode (micro-LED) display featuring fingerprint detection without any additional light emitting and sensing devices in mobile applications. This paper proposes that conventional LEDs can be used as photodetectors in active-matrix pixel circuits. In the area where a finger touched, some LEDs are used as photodetectors and others are used as light emitting sources. The photocurrents of reverse-biased LEDs under various illumination conditions were investigated. The active-matrix circuit was fabricated using a conventional p-type low-temperature polycrystalline silicon (LTPS) process. The fabricated pixel circuit could distinguish the intensity of the incident light to the sensing LED. The voltage across the sensing LED (VLED) was investigated when the pixel density was 400 pixels per inch (ppi) and the cover glass thickness was 30 μm. The experimental results showed that the VLED changed by 0.5 V for 16.7 ms when red, green, or blue LEDs emitted 150 cd/m 2 , 400 cd/m 2 , or 100 cd/m 2 , respectively. 19 LED array with 1.5 mm pitch (p) and 2 mm thick cover glass was fabricated to emulate the LED display with 400 ppi and 30 μm thick cover glass. It is found that an emitting LED affected the sensing LEDs within the distance of 3p by comparing VLEDs. VLEDs were measured when the material on the cover glass was air and water with white pigments (water/W). ΔVLEDs were 0.29 V and 1.13 V for glass-air and glass-water/W cases, respectively. It is found that the lights incident on the sensing LED comprised not only reflected lights by Fresnel reflection at the glass interface but also scattered lights in the water/W. A 75 magnified fake fingerprint was fabricated. Its material was poly-lactic acid with refractive index of 1.465 which is very close to that of a fingertip. Measured ΔVLEDs at ridges and valleys were 0.48 V and 0.22 V, respectively. The ratio of 0.48 / 0.22 was 2.18 that is very close to 1.91 that is the ratio of light intensity at the ridge to that at the valley obtained by the calculation. This verifies that the proposed micro-LED display distinguishes the ridges and valleys of fingerprint without any help from any additional devices.

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Section: Resultsmentioning

confidence: 99%

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

et al. 2022

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“…In our previous work, we have reported that the conventional TFT with a gap region between gate and drain, which is called Gap-Type TFT, can be used as a photo sensor [5]. Moreover, we also proposed the photosensitive mechanism of this device with a-Si as the semiconductor layer which is called the LIBL effect.…”

Section: Device Structure and Fabrication (1) Semiconductor Materialsmentioning

confidence: 99%

62‐3: Infrared Sensitive Thin‐Film Phototransistor Made on Glass Substrate for Active Matrix Sensing Application

Yuan,

Tai,

Tsai

et al. 2023

Symp Digest of Tech Papers

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In this paper, we propose a novel approach to IR sensing using a narrow band gap semiconductor and the light‐induced barrier lowering (LIBL) mechanism. Lead sulfide quantum dots (PbS QDs) were used as the semiconductor material due to their ideal bandgap energy for IR sensing. The proposed TFT sensor structures with and without a gap between gate and drain were fabricated and demonstrated excellent sensitivity to IR radiation, and therefore providing a cost‐effective and accessible solution for IR sensing, with potential applications in various fields.

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“…In previous research [3][4] [5][6], we introduced Gap-type amorphous silicon (a-Si) thin-film transistor (TFT). This type of TFT has a gap region between the gate and drain, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

47‐1: Ambipolar Gap‐type a‐Si‐TFT Circuit Applied for a Color Ambient Light Sensor

Lin,

Yuan,

Tai

et al. 2023

Symp Digest of Tech Papers

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In this paper, we proposed ambient light sensor (ALS) and color temperature sensor (CTS) circuit integrated in the edge of LCD display panel. The designed circuit is based on the thin film transistor (TFT) technology, the photo TFT can produce high photo current under light for sensor realizing ambient light from 0~50000Lux. Also, CTS circuit are based on ALS circuit but covered with color filter. The result shows that CTS can discriminate different color temperature in ambient light. The biggest advantage of this sensor is that it is compatible with TFT process in manufacturing, and it is small in size and high in efficiency. It has the potential to replace photodiode sensors.

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Light-Controlled Gap-Type TFT Used for Large-Area Under-Screen Fingerprint Sensor

Cited by 15 publications

References 11 publications

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

Novel Micro-LED Display Featuring Fingerprint Recognition Without Additional Sensors

62‐3: Infrared Sensitive Thin‐Film Phototransistor Made on Glass Substrate for Active Matrix Sensing Application

47‐1: Ambipolar Gap‐type a‐Si‐TFT Circuit Applied for a Color Ambient Light Sensor

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