Photocurrent decay from the steady-state in thin film hydrogenated amorphous silicon: Numerical simulation analysis of experimental results

ABSTRACTThe experimental results regarding to the effects of ultraviolet (UV) light illumination on the characteristics of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFT's) have been presented. The device parameters of a-Si:H TFT, such as threshold voltage, field-effect mobility, and subthreshold slope, have been degraded by electrical stress and visible light illumination, but substantially improved by UV radiation. This may be attributed to an annealing effect on the dangling-bond defects, involving a number of phonons generated by absorption of high energy UV photons in the a-Si:H TFT channel. It has been also observed that the off-current of a-Si:H TFT decreases remarkably while the on-current changes very little. From the experimental results, we report that the improved on/off current ratio of a-Si:H TFT may be achieved by UV radiation.

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Numerical simulation of the steady state photoconductivity in hydrogenated amorphous silicon including localized state electron hopping

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/18/15/017 ◽

2006 ◽

Vol 18 (15) ◽

pp. 3721-3734 ◽

Cited By ~ 8

Author(s):

A Merazga ◽

S Tobbeche ◽

C Main ◽

A Al-Shahrani ◽

S Reynolds

Keyword(s):

Numerical Simulation ◽

Steady State ◽

Amorphous Silicon ◽

Hydrogenated Amorphous Silicon ◽

Electron Hopping ◽

Localized State ◽

State Electron ◽

Hydrogenated Amorphous

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Hydrogenated Nanocrystalline Silicon Thin Film Transistor Array for X-ray Detector Application

MRS Proceedings ◽

10.1557/proc-1066-a16-07 ◽

2008 ◽

Vol 1066 ◽

Author(s):

Kyung-Wook Shin ◽

Mohammad R. Esmaeili-Rad ◽

Andrei Sazonov ◽

Arokia Nathan

Keyword(s):

Thin Film ◽

Amorphous Silicon ◽

Threshold Voltage ◽

Hydrogenated Amorphous Silicon ◽

Nanocrystalline Silicon ◽

Amorphous Selenium ◽

Breakdown Field ◽

Storage Capacitor ◽

X Ray ◽

Hydrogenated Amorphous

ABSTRACTHydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF) of 0.15 cm2/V·s, a threshold voltage (VTh) of 5.71 V, and a subthreshold leakage current (Isub) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.

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