Structure Sensitive Hydrogenation Effects in Polysilicon High Voltage thin Film Transistors

1999 ◽  
Vol 557 ◽  
Author(s):  
F.J. Clough ◽  
Y.Z. Xu ◽  
E.M. Sankara Narayanan ◽  
R. Cross
Keyword(s):  
Carrier Transport ◽  
Defect Density ◽  
Operating Performance ◽  
Rf Plasma ◽  
Hydrogen Passivation ◽  
Process Step ◽  
Field Plate ◽  
Structure Sensitive ◽  
Hydrogenation Time ◽  
Plasma Hydrogenation

AbstractHydrogen passivation of grain boundary and in-grain defects is a key process step in the fabrication of high quality poly-Si TFTs. The sensitivity of the hydrogenation process to device geometry is therefore an important consideration. The effects of rf-plasma hydrogenation on the operating performance of a range of self-aligned and offset drain (Loff = 5 to 40 μm) poly-Si TFT configurations is reported. The hydrogenation of offset drain structures results in a predictable increase in the pre-threshold slope and a reduction in the device threshold voltage. However, extended hydrogenation (up to 12 h) can result in a significant reduction in the device drive current (by up to 2 orders). A similar effect is observed in metal field plate HVTFTs in which some portion of the offset region is un-modulated by the additional electrode. The on state conduction in the offset region is examined as a function of hydrogenation time, temperature and planar electric field. The increase in the on resistance is attributed to a reduction in the poly-Si defect density, which moderates carrier transport through the offset region.

scholarly journals Designs of InGaN Micro-LED Structure for Improving Quantum Efficiency at Low Current Density

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Shiqiang Lu ◽  
Jinchai Li ◽  
Kai Huang ◽  
Guozhen Liu ◽  
Yinghui Zhou ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Current Density ◽  
Carrier Transport ◽  
Defect Density ◽  
Numerical Study ◽  
Structure Design ◽  
Operating Conditions ◽  
Hole Injection ◽  
Electron Blocking Layer ◽  
Recombination Processes

AbstractHere we report a comprehensive numerical study for the operating behavior and physical mechanism of nitride micro-light-emitting-diode (micro-LED) at low current density. Analysis for the polarization effect shows that micro-LED suffers a severer quantum-confined Stark effect at low current density, which poses challenges for improving efficiency and realizing stable full-color emission. Carrier transport and matching are analyzed to determine the best operating conditions and optimize the structure design of micro-LED at low current density. It is shown that less quantum well number in the active region enhances carrier matching and radiative recombination rate, leading to higher quantum efficiency and output power. Effectiveness of the electron blocking layer (EBL) for micro-LED is discussed. By removing the EBL, the electron confinement and hole injection are found to be improved simultaneously, hence the emission of micro-LED is enhanced significantly at low current density. The recombination processes regarding Auger and Shockley–Read–Hall are investigated, and the sensitivity to defect is highlighted for micro-LED at low current density.Synopsis: The polarization-induced QCSE, the carrier transport and matching, and recombination processes of InGaN micro-LEDs operating at low current density are numerically investigated. Based on the understanding of these device behaviors and mechanisms, specifically designed epitaxial structures including two QWs, highly doped or without EBL and p-GaN with high hole concentration for the efficient micro-LED emissive display are proposed. The sensitivity to defect density is also highlighted for micro-LED.

scholarly journals Low Dark Current and Performance Enhanced Perovskite Photodetector by Graphene Oxide as an Interfacial Layer

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 190
Author(s):  
Ali Hassan ◽  
Muhammad Azam ◽  
Yeong Hwan Ahn ◽  
Muhammad Zubair ◽  
Yu Cao ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Dark Current ◽  
High Performance ◽  
Carrier Transport ◽  
Defect Density ◽  
Low Cost ◽  
Degradation Process ◽  
Device Performance ◽  
Interface Engineering ◽  
Defect Passivation

Organic–inorganic hybrid perovskite photodetectors are gaining much interest recently for their high performance in photodetection, due to excellent light absorption, low cost, and ease of fabrication. Lower defect density and large grain size are always favorable for efficient and stable devices. Herein, we applied the interface engineering technique for hybrid trilayer (TiO2/graphene oxide/perovskite) photodetector to attain better crystallinity and defect passivation. The graphene oxide (GO) sandwich layer has been introduced in the perovskite photodetector for improved crystallization, better charge extraction, low dark current, and enhanced carrier lifetime. Moreover, the trilayer photodetector exhibits improved device performance with a high on/off ratio of 1.3 × 104, high responsivity of 3.38 AW−1, and low dark current of 1.55 × 10−11 A. The insertion of the GO layer also suppressed the perovskite degradation process and consequently improved the device stability. The current study focuses on the significance of interface engineering to boost device performance by improving interfacial defect passivation and better carrier transport.

scholarly journals Relationship between defect density and charge carrier transport in amorphous and microcrystalline silicon

2009 ◽  
Vol 79 (10) ◽  
Author(s):  
Oleksandr Astakhov ◽  
Reinhard Carius ◽  
Friedhelm Finger ◽  
Yuri Petrusenko ◽  
Valery Borysenko ◽  
...  
Keyword(s):  
Charge Carrier ◽  
Carrier Transport ◽  
Defect Density ◽  
Charge Carrier Transport ◽  
Microcrystalline Silicon

Growth of a-plane ZnO Thin Films on r-plane Sapphire by Plasma-assisted MBE

2005 ◽  
Vol 891 ◽  
Author(s):  
Junqing Q. Xie ◽  
J. W. Dong ◽  
A. Osinsky ◽  
P. P. Chow ◽  
Y. W. Heo ◽  
...  
Keyword(s):  
Thin Films ◽  
Lattice Mismatch ◽  
Defect Density ◽  
Zno Thin Films ◽  
Rf Plasma ◽  
Misfit Dislocations ◽  
Epitaxial Relationship ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Small Lattice

ABSTRACTZnO thin films have been epitaxially grown on r-plane sapphire by RF-plasma-assisted molecular beam epitaxy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicate that the epitaxial relationship between ZnO and r-plane sapphire is (1120)ZnO // (1102)sapphire and [0001]ZnO // [1101]sapphire. Atomic force microscopy measurements reveal islands extended along the sapphire [1101] direction. XRD omega rocking curves for the ZnO (1120) reflection measured either parallel or perpendicular to the island direction suggest the defect density anisotropy along these directions. Due to the small lattice mismatch along the ZnO [0001] direction, few misfit dislocations were observed at the ZnO/Al2O3 interface in the high-resolution cross-sectional TEM image with the zone axis along the ZnO [1100] direction.

Carrier Transport in Polycrystalline and Amorphous Silicon Thin Film Transistors

1994 ◽  
Vol 358 ◽  
Author(s):  
T. Sameshima ◽  
M. Sekiya ◽  
M. Hara ◽  
N. Sano ◽  
A. Kohno
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Thin Film Transistors ◽  
Carrier Transport ◽  
Defect Density ◽  
Inversion Layer ◽  
Chemical Vapor ◽  
Laser Crystallization ◽  
Silicon Thin Film ◽  
Plasma Chemical Vapor Deposition

ABSTRACTThe technologies of laser crystallization and methods of SiO2 formation in remote plasma chemical vapor deposition or SiO evaporation with an oxygen ambient realize the fabrication of n-channel polycrystalline and amorphous silicon thin film transistors (poly-Si and a-Si TFTs) at a temperature lower than 300 °C. The defect density was achieved to be 2∼3×1011 cm−2eV−1 and threshold voltage was about IV for both TFTs. The maximum field effect mobility was 600 cm2/Vs for poly-Si TFTs and 2.6 cm2/Vs for a-Si TFTs. The mobility of poly-Si TFT decreased as the gate voltage increases. This is interpreted as that the electrons are confined in the narrow inversion layer and electron scattering with phonon is enhanced for higher normal electric field.

scholarly journals Correlation of Electrical Properties With Defects in A Homoepitaxial Chemical-Vapor-Deposited Diamond

1995 ◽  
Vol 416 ◽  
Author(s):  
S. Han ◽  
G. Rodriguez ◽  
A. Taylori ◽  
M. A. Plano ◽  
M. D. Moyer ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Diamond Film ◽  
Carrier Transport ◽  
Defect Density ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Limiting Factor ◽  
X Ray Diffraction ◽  
Density Region ◽  
X Ray

ABSTRACTA high-quality, low-stress 200 gim epitaxial diamond film has been grown on a 400 μm thick high-temperature-high-pressure Ila diamond. X-ray diffraction images of the film indicate that a large region of the film is fairly defect free and individual dislocations have been imaged in this region. Depth-resolved Raman results indicate that the region of the film with a low density of defects also has lower stress than in the higher defect density region. Transient photoconductivity measurements were performed on the high and low line defect density regions of the homoepitaxial diamond film to determine the effects of the stress and defect density on the combined electron-hole mobility and carrier lifetime. The correlation between the electrical properties and the x-ray diffraction imaging suggests that line defects may not be the limiting factor in the carrier transport at the present film quality

scholarly journals Growth Condition-Oriented Defect Engineering for Changes in Au–ZnO Contact Behavior from Schottky to Ohmic and Vice Versa

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 980 ◽  
Author(s):  
Abu Rana ◽  
Hyun-Seok Kim
Keyword(s):  
Schottky Barrier ◽  
Carrier Concentration ◽  
Carrier Transport ◽  
Defect Density ◽  
High Surface ◽  
Zno Nanorods ◽  
Schottky Contact ◽  
Oxygen Plasma Treatment ◽  
Defect Engineering ◽  
Contact Behavior

ZnO has the built-in characteristics of both ionic and covalent compound semiconductors, which makes the metal–ZnO carrier transport mechanism quite intricate. The growth mechanism-centric change in ZnO defect density and carrier concentration also makes the contact formation and behavior unpredictable. This study investigates the uncertainty in Au–ZnO contact behavior for application-oriented research and the development on ZnO nanostructures. Herein, we explain the phenomenon for how Au–ZnO contact could be rectifying or non-rectifying. Growth method-dependent defect engineering was exploited to explain the change in Schottky barrier heights at the Au–ZnO interface, and the change in device characteristics from Schottky to Ohmic and vice versa. The ZnO nanorods were fabricated via aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. For further investigations, one ACG sample was doped with Ga, and another was subjected to oxygen plasma treatment (OPT). The ACG and Ga-doped ACG samples showed a quasi-Ohmic and Ohmic behavior, respectively, because of a high surface and subsurface level donor defect-centric Schottky barrier pinning at the Au–ZnO interface. However, the ACG-OPT and MAG samples showed a more pronounced Schottky contact because of the presence of low defect-centric carrier concentration via MAG, and the removal of the surface accumulation layer via the OPT process.

scholarly journals Towards Quantitative Interpretation of Fourier-Transform Photocurrent Spectroscopy on Thin-Film Solar Cells

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 820
Author(s):  
Jakub Holovský ◽  
Michael Stuckelberger ◽  
Tomáš Finsterle ◽  
Brianna Conrad ◽  
Amalraj Peter Amalathas ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Solar Cells ◽  
Carrier Transport ◽  
Open Circuit Voltage ◽  
Defect Density ◽  
Open Circuit ◽  
Absorption Enhancement ◽  
Thickness Variation ◽  
Accurate Analysis ◽  
Photocurrent Spectroscopy

The method of detecting deep defects in photovoltaic materials by Fourier-Transform Photocurrent Spectroscopy has gone through continuous development during the last two decades. Still, giving quantitative predictions of photovoltaic device performance is a challenging task. As new materials appear, a prediction of potentially achievable open-circuit voltage with respect to bandgap is highly desirable. From thermodynamics, a prediction can be made based on the radiative limit, neglecting non-radiative recombination and carrier transport effects. Beyond this, more accurate analysis has to be done. First, the absolute defect density has to be calculated, taking into account optical effects, such as absorption enhancement, due to scattering. Secondly, the electrical effect of thickness variation has to be addressed. We analyzed a series of state-of-the-art hydrogenated amorphous silicon solar cells of different thicknesses at different states of light soaking degradation. Based on a combination of empirical results with optical, electrical and thermodynamic simulations, we provide a predictive model of the open-circuit voltage of a device with a given defect density and absorber thickness. We observed that, rather than the defect density or thickness alone, it is their product or the total number of defects, that matters. Alternatively, including defect absorption into the thermodynamic radiative limit gives close upper bounds to the open-circuit voltage with the advantage of a much easier evaluation.

Modeling of depletion width variation over time in thin film photovoltaics

2016 ◽  
Vol 30 (05) ◽  
pp. 1650044 ◽  
Author(s):  
Marouf Aldosari ◽  
Liliana Grigoriu ◽  
Hamed Sohrabpoor ◽  
Nima E. Gorji
Keyword(s):  
Thin Film ◽  
Carrier Transport ◽  
Defect Density ◽  
Depletion Region ◽  
Time Dependent ◽  
Perovskite Layer ◽  
Tunneling Mechanism ◽  
Depletion Width ◽  
Thin Film Photovoltaics ◽  
Over Time

The performance degradation of a hybrid solar cell is modelled considering the variation of depletion width over time. The p-i-n structure of a TiO2/perovskite/HTL photovoltaic is investigated. Several different time-dependent approaches are compared and a new model is introduced based on the variation of defect density over time in depletion region. This phenomenon consequently manifests itself in the device degradation. Our approach leads to rather complicated time-dependent equation for the defect density which takes into account also the non-uniformity of electric field in the depletion region. The thickness of TiO2 nano layer is taken 50 nm and perovskite layer is 330 nm. The nanoscale thickness of TiO2 layer warrants the carrier transport through tunneling mechanism.

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