Near-Intrinsic Microcrystalline Silicon for Use in Thin Film Transistors

1997 ◽  
Vol 467 ◽  
Author(s):  
M. W. D. Froggatt ◽  
W. I. Milne ◽  
M. J. Powell
Keyword(s):  
Thin Film ◽  
Activation Energy ◽  
Thin Film Transistors ◽  
Chemical Vapour ◽  
Contact Layer ◽  
Dark Conductivity ◽  
Dilution Method ◽  
Microcrystalline Silicon ◽  
High Hydrogen ◽  
Channel Region

ABSTRACTInverted-staggered thin film transistors (TFTs) incorporating hydrogenated microcrystalline silicon for both contact and channel regions have been fabricated by plasma enhanced chemical vapour deposition (PECVD) using the high hydrogen-dilution method. The deposition parameters for the channel region were chosen to yield near-intrinsic material with a dark conductivity activation energy of 0.7 eV and a Tauc gap of 1.98 eV, while the doped contact layer was optimised to produce a high dark conductivity of 10 S/cm.These devices exhibit a low off-current but the field effect mobility is found to be lower than that of similar devices incorporating an optimised amorphous silicon channel region. The mobility activation energy in these devices is similar to those incorporating an amorphous channel, but the mobility pre-factor is reduced. We propose that this is due to inhomogeneous conduction through a microcrystalline region with a smaller grain size at the dielectric/channel interface.

The Effect of Hydrogen Dilution on Hot-Wire Thin-Film Transistors

1998 ◽  
Vol 507 ◽  
Author(s):  
J.P. Conde ◽  
H. Silva ◽  
V. Chu
Keyword(s):  
Thin Film ◽  
Active Layer ◽  
Thin Film Transistors ◽  
Silicon Layer ◽  
Active Layer Thickness ◽  
Hot Wire ◽  
Microcrystalline Silicon ◽  
High Hydrogen ◽  
Hydrogen Dilution ◽  
Active Layers

ABSTRACTBottom-gate thin film transistors (TFT) were fabricated with amorphous and microcrystalline silicon active layers deposited by hot-wire (HW) chemical vapor deposition using different levels of hydrogen dilution. As the hydrogen dilution was increased above 80%, the active layer made a transition from amorphous to microcrystalline. This transition resulted in an increase of the TFT off-current and in an increase of the TFT subthreshold slope. The TFT on- current and the TFT mobility remained at levels comparable to those of the a-Si:H HW TFTs. A comparison is made between TFTs with amorphous and microcrystalline silicon active layers prepared both by rf glow discharge and HW. HW TFTs with an active layer consisting of a thin layer deposited with high hydrogen dilution underlying a thicker amorphous silicon layer are also compared to TFTs with an active layer of the same total active layer thickness consisting only of the high hydrogen dilution film.

Intrinsic microcrystalline silicon by postgrowth anneals

2001 ◽  
Vol 16 (6) ◽  
pp. 1531-1534 ◽  
Author(s):  
Jong-Hwan Yoon
Keyword(s):  
Activation Energy ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Microcrystalline Silicon ◽  
Conductivity Activation Energy ◽  
High Hydrogen ◽  
Constant Rate ◽  
Annealing Cycle

Hydrogenated microcrystalline silicon (μc-Si:H) grown by a conventional plasma-enhanced chemical vapor deposition from high hydrogen-diluted silane was annealed by increasing the temperature from 25 to 450 °C at a constant rate of 12 °C/min (one annealing cycle). Dark-conductivity activation energy gradually increases with increasing the number of annealing cycle to a saturation value of about 0.6 eV, observed in truly intrinsic μc-Si:H films. For the saturated state, the dark conductivity of the order of 10−8 S/cm was obtained. Little or no change in the oxygen content was observed after the annealing.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

Effect of Illumination on Organic Polymer Thin-Film Transistors

2003 ◽  
Vol 771 ◽  
Author(s):  
Michael C. Hamilton ◽  
Sandrine Martin ◽  
Jerzy Kanicki
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Drain Current ◽  
Charge Carriers ◽  
Electrical Performance ◽  
Organic Polymer ◽  
Light Illumination ◽  
Polymer Thin Film ◽  
Channel Region ◽  
White Light Illumination

AbstractWe have investigated the effects of white-light illumination on the electrical performance of organic polymer thin-film transistors (OP-TFTs). The OFF-state drain current is significantly increased, while the drain current in the strong accumulation regime is relatively unaffected. At the same time, the threshold voltage is decreased and the subthreshold slope is increased, while the field-effect mobility of the charge carriers is not affected. The observed effects are explained in terms of the photogeneration of free charge carriers in the channel region due to the absorbed photons.

Influence of the deposition temperature on the performance of microcrystalline silicon thin film transistors

2008 ◽  
Vol 52 (3) ◽  
pp. 432-435 ◽  
Author(s):  
Maher Oudwan ◽  
Alexey Abramov ◽  
Pere Roca i Cabarrocas ◽  
François Templier
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Deposition Temperature ◽  
Microcrystalline Silicon ◽  
Silicon Thin Film

High Mobility ZnO thin film transistors using the novel deposition of high-k dielectrics

2011 ◽  
Vol 1315 ◽  
Author(s):  
D. K. Ngwashi ◽  
R. B. M. Cross ◽  
S. Paul ◽  
Andrian P. Milanov ◽  
Anjana Devi
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Performance Metrics ◽  
Chemical Vapour ◽  
High Mobility ◽  
Hafnium Dioxide ◽  
Organic Chemical ◽  
Channel Mobility ◽  
High K ◽  
Metal Organic

ABSTRACTIn order to investigate the performance of ZnO-based thin film transistors (ZnO-TFTs), we fabricate devices using amorphous hafnium dioxide (HfO2) high-k dielectrics. Sputtered ZnO was used as the active channel layer, and aluminium source/drain electrodes were deposited by thermal evaporation, and the HfO2 high-k dielectrics are deposited by metal-organic chemical vapour deposition (MOCVD). The ZnO-TFTs with high-k HfO2 gate insulators exhibit good performance metrics and effective channel mobility which is appreciably higher in comparison to SiO2-based ZnO TFTs fabricated under similar conditions. The average channel mobility, turn-on voltage, on-off current ratio and subthreshold swing of the high-k TFTs are 31.2 cm2V-1s-1, -4.7 V, ~103, and 2.4 V/dec respectively. We compared the characteristics of a typical device consisting of HfO2 to those of a device consisting of thermally grown SiO2 to examine their potential for use as high-k dielectrics in future TFT devices.

Low temperature processed p-type bottom gate microcrystalline silicon thin film transistors

2010 ◽  
pp. NA-NA
Author(s):  
O. Moustapha ◽  
A. Abramov ◽  
D. Daineka ◽  
M. Oudwan ◽  
Y. Bonnassieux ◽  
...  
Keyword(s):  
Thin Film ◽  
Low Temperature ◽  
Thin Film Transistors ◽  
Microcrystalline Silicon ◽  
Silicon Thin Film ◽  
P Type ◽  
Bottom Gate

Mechanisms for Defect Creation and Removal in Hydrogenated and Deuterated Amorphous Silicon Studied using Thin Film Transistors

2006 ◽  
Vol 910 ◽  
Author(s):  
Andew Flewitt ◽  
Shufan Lin ◽  
William I Milne ◽  
Ralf B Wehrspohn ◽  
Martin J Powell
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Threshold Voltage ◽  
Thin Film Transistors ◽  
Elevated Temperatures ◽  
Chemical Vapour ◽  
Rf Plasma ◽  
Gate Bias ◽  
Removal Process ◽  
Defect Creation

AbstractIt has been widely observed that thin film transistors (TFTs) incorporating an hydrogenated amorphous silicon (a-Si:H) channel exhibit a progressive shift in their threshold voltage with time upon application of a gate bias. This is attributed to the creation of metastable defects in the a-Si:H which can be removed by annealing the device at elevated temperatures with no bias applied to the gate, causing the threshold voltage to return to its original value. In this work, the defect creation and removal process has been investigated using both fully hydrogenated and fully deuterated amorphous silicon (a-Si:D) TFTs. In both cases, material was deposited by rf plasma enhanced chemical vapour deposition over a range of gas pressures to cover the a-g transition. The variation in threshold voltage as a function of gate bias stressing time, and annealing time with no gate bias, was measured. Using the thermalisation energy concept, it has been possible to quantitatively determine the distribution of energies required for defect creation and removal as well as the associated attempt-to-escape frequencies. The defect creation and removal process in a-Si:H is then discussed in the light of these results.

scholarly journals Investigation on stability of microcrystalline silicon thin film transistors

2006 ◽  
Vol 55 (12) ◽  
pp. 6612
Author(s):  
Li Juan ◽  
Wu Chun-Ya ◽  
Zhao Shu-Yun ◽  
Liu Jian-Ping ◽  
Meng Zhi-Guo ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Microcrystalline Silicon ◽  
Silicon Thin Film

n+-doped-layer-free microcrystalline silicon thin film transistors fabricated with the CuMg as source/drain metal

2007 ◽  
Vol 91 (2) ◽  
pp. 022113 ◽  
Author(s):  
M. C. Wang ◽  
T. C. Chang ◽  
Po-Tsun Liu ◽  
R. W. Xiao ◽  
L. F. Lin ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Microcrystalline Silicon ◽  
Silicon Thin Film
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