Abstract
Amorphous indium- gallium-zinc oxide (a-IGZO) has been intensively studied for the application to active matrix flat-panel display because of its superior electrical and optical properties. However, the characteristics of a-IGZO were found to be very sensitive to external circumstance such as light illumination, which dramatically degrades the device performance and stability practically required for display applications. Here, we suggest the use for silicon-germanium (Si-Ge) films grown plasma-enhanced chemical vapour deposition (PECVD) as photo-blocking layers in the a-IGZO thin film transistors (TFTs). The charge mobility and threshold voltage (Vth) of the TFTs depend on the thickness of the Si-Ge films and dielectric buffer layers (SiNX), which were carefully optimized to be ~200 nm and ~300 nm, respectively. As a result, even after 1,000 s illumination time, the Vth and electron mobility of the TFTs remain unchanged, which was enabled by the photo-blocking effect of the Si-Ge layers for a-IGZO films. Considering the simple fabrication process by PECVD with outstanding scalability, we expect that this method can be widely applied to TFT devices that are sensitive to light illumination.
Highlights
As a panel size has been changed to large scale screen size in the active-matrix flat panel displays, many researchers have investigated in transparent metal oxide semiconductors instead of amorphous silicon because of their high mobility and low synthesis temperature (~250 °C)[1,2,3]
We suggest the silicon-germanium (Si-Ge) films as the photo-blocking layers in Amorphous indium- gallium-zinc oxide (a-IGZO) based thin film transistors (TFTs)
The Si-Ge films were synthesized on glass substrates coated by silicon oxide by plasma-enhanced chemical vapor deposition (PECVD)
Summary
As a panel size has been changed to large scale screen size in the active-matrix flat panel displays, many researchers have investigated in transparent metal oxide semiconductors instead of amorphous silicon because of their high mobility and low synthesis temperature (~250 °C)[1,2,3]. A-IGZO based thin film transistors (TFTs) have attracted more attention due to its transparent optical properties and convenient synthesis methods at low temperature with reasonable cost[5]. A few research groups have focused on metal based photo blocking layers for a-IGZO films[16,17,18]. The metal based photo blocking layers prevent the reaction of a-IGZO films from the backlight, the performance of the a-IGZO TFTs is decreased due to the increased cap size between metal and IGZO. We suggest the silicon-germanium (Si-Ge) films as the photo-blocking layers in a-IGZO based TFTs. According to preceding research, ultraviolet (UV) absorbance is increased in the Si-Ge alloy which have www.nature.com/scientificreports/. It was found that TFTs with Si-Ge photo blocking layers preserved the initial value including mobility and threshold voltage (Vth) without any oxidation or chemical damages under the light illumination
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