Chia-Tien Peng

Integrated Ambient Light Sensor With Nanocrystalline Silicon on a Low-Temperature Polysilicon Display Panel

A novel integrated ambient light sensor using nanocrystalline silicon fabricated using low-temperature polysilicon technology has been developed on a display panel. The photosensing structure of the silicon nanocrystals embedded in a dielectric film sandwiched between the bottom metal and top indium-thin-oxide electrodes perfectly eliminates backlight noise, which is a problem typical of conventional p-i-n photodiodes integrated into a liquid-crystal display. Experimental results indicate that the Si-nanocrystal photosensor has better performances in dark current and quantum efficiency than those of the p-i-n diode. The Si-nanocrystal photosensor also exhibited response linearity and speed comparable to the p-i-n diode. In terms of long-term operation and reliability, the lifetime of the Si-nanocrystal photosensor is roughly two orders longer than that of the p-i-n diode. The Si-nanocrystal ambient light sensor has considerable flexibility in the design of spectrum, geometry, and the readout circuit, which is achieved by adjusting the nanocrystal size and applying a vertical stacking structure. The Si-nanocrystal photosensor can be a promising low-cost PMOS-only solution for various photosensing applications on display panels.

Silicon-nanocrystal-based photosensor integrated on low-temperature polysilicon panels

— A photodetector using a silicon-nanocrystal layer sandwiched between two electrodes is proposed and demonstrated on a glass substrate fabricated by low-temperature poly-silicon (LTPS) technology. Through post excimer-laser annealing (ELA) of silicon-rich oxide films, silicon nanocrystals formed between the bottom metal and top indium thin oxide (ITO) layers exhibit good uniformity, reliable optical response, and tunable absorption spectrum. Due to the quantum confinement effect leading to enhanced phonon-assisted excitation, these silicon nanocrystals, less than 10 nm in diameter, promote electron-hole-pair generation in the photo-sensing region as a result resembling a direct-gap transition. The desired optical absorption spectrum can be obtained by determining the thickness and silicon concentration of the deposited silicon-rich oxide films as well as the power of post laser annealing. In addition to obtaining a photosensitivity comparable to that of the p-i-n photodiode currently used in LTPS technology, the silicon-nanocrystal-based photosensor provides an effective backlight shielding by the bottom electrode made of molybdenum (Mo). Having a higher temperature tolerance for both the dark current and optical responsibility and maximizing the photosensing area in a pixel circuit by adopting a stack structure, this novel photosensor can be a promising candidate for realizing an optical touch function on a LTPS panel.

16.1: Distinguished Paper: Rollable Electrophoretic Display with Amorphous‐Silicon Gate Driver Circuit Integrated

Highly flexible electrophoretic display with gate driver circuits integrated was demonstrated. Beginning from the essential components such as TFTs, resistors and capacitors, the authors finally design a GOA-embedded display which can withstand 10,000 rolling cycles of 20 mm radius without any line defect and optic performance degradation.

22.4: In‐Cell Multiple Ambient Light Sensor (ALSs) LCD Integration Using Si‐based Photonic Sensor by a‐Si TFT Technology

We have developed a new AMLCD with multiple ambient light sensors (ALSs) for reducing backlight (BL) power consumption, and false sensing of ambient illuminance. ALSs perform well in showing BL control for power-saving, even though one of the sensors is covered by a finger shadow. Architecture of integrated ALS with a-Si and LTPS technologies are presented. We fabricate the in-cell, and wide-dynamic-sensing ALSs display using new light sensor technology. Photo-electrical characteristics with well linearity and reliability under long-term operation were observed.

P-199L: Late-News Poster: Silicon Nanocrystals Photo Sensor Integrated on Low-Temperature Polycrystalline-Silicon Panels

A photo-detector using silicon nanocrystal layer sandwiched between two electrodes is first time proposed and demonstrated for photo-sensing application on LTPS panels. Through post-annealing of silicon rich oxide films, Si nanocrystals can be formed with good uniformity and high temperature tolerance to respond best to certain absorption spectrum of the corresponding light source. These silicon nanocrystals, less than 10nm in diameter, exhibit better quantum confinement effect, which promote electron-hole pair generation in photo-sensing region as a result of its direct bandgap. In addition to obtaining photo sensitivity superior to that of a P-I-N diode currently used in LTPS technology, the new sensor can maximize the fill factor in a pixel circuit by adapting a stacked structure.