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

Abstract

Abstract— 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.

Optical Properties of a-SiGe:H Thin Film Transistor for Infrared Image Sensors in Touch Sensing Display

“…Also, theoretically higher touch resolutions as well as much lower cost for touch function are expected when sensors are inserted in each pixel [1], [2]. Many different in-cell touch technologies have been developed to implement multi-touch functions into the display panel, such as the digital switching technology [3], the projected capacitive method [4], [5] and the photo sensor type [6]- [8]. These have their own advantages over other methods that they have been applied in a different sized or types of display panel.…”

“…In case of the photo-type in-cell touch, the concept of putting a light-sensing element into each pixel was first introduced in 2003 [9], and after that, several materials like a-Si or low temperature poly-silicon optical sensors were successfully embedded into small-sized LCD panel [6]- [8]. Recently photo type in-cell touch panel using continuous grain silicon was firstly produced commercially at touch pad [2].…”