Visible Light Emitting Diode Employing Electrochemically Anodized Nanocrystalline Silicon Thin Film

1996 ◽  
Vol 452 ◽  
Author(s):  
T. Toyama ◽  
T. Yamamoto ◽  
T. Matsui ◽  
H. Okamoto
Keyword(s):  
Thin Film ◽  
Light Emitting Diode ◽  
Light Output ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Rf Plasma ◽  
Silicon Thin Film ◽  
Light Emitting ◽  
Plasma Chemical Vapor Deposition ◽  
Boron Doped

AbstractVisible electroluminescence (EL) has been achieved on the entirely solid state thin film light emitting diode (TFLED) employing electrochemically anodized nanocrystalline Si (nc-Si) as a light emitting active layer. The TFLED consisting of p-type nc-Si, and intrinsic and n-type amorphous layers was fabricated on a SnO2-coated glass substrate. The nc-Si was formed in HF aqueous solution from boron doped microcrystalline Si (μc-Si) deposited by rf plasma chemical vapor deposition (CVD). The TFLED exhibits clear rectification with a forward threshold voltage of about 1.5 V, whereas visible EL emission is observed upon applying reverse bias voltages. The diode ideality factor is more than 2, and the light output increases with the square of the diode current. The EL emission color is orange-red and the spectral peak energy is 1.8 eV.

Hydrogen in Ultralow Temperature SiO2for Nanocrystalline Silicon Thin Film Transistors

2004 ◽  
Vol 814 ◽  
Author(s):  
Alex Kattamis ◽  
I-Chun Cheng ◽  
Steve Allen ◽  
Sigurd Wagner
Keyword(s):  
Thin Film ◽  
Leakage Current ◽  
Current Density ◽  
Thin Film Transistors ◽  
Secondary Ion Mass Spectrometry ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Film Deposition ◽  
Silicon Thin Film

AbstractNanocrystalline silicon is a candidate material for fabricating thin film transistors with high carrier mobilities on plastic substrates. A major issue in the processing of nanocrystalline silicon thin film transistors (nc-Si:H TFTs) at ultralow temperatures is the quality of the SiO2gate dielectric. SiO2deposited at less than 250°C by radio frequency plasma enhanced chemical vapor deposition (rf-PECVD), and not annealed at high temperature after deposition, exhibits high leakage current and voltage shifts when incorporated into TFT's. Secondary ion mass spectrometry (SIMS) measurements show that the hydrogen concentration (NH) in PECVD oxide deposited at 150°C on crystalline silicon (x-Si) is ∼ 0.8 at. %. This is much higher than in thermal oxides on x-Si, which display concentrations of less than 0.003 at. %. The leakage current density for thermal oxides on x-Si at a bias of 10 V is ∼9×10−6A/cm2whereas for 200°C PECVD oxides on nc-Si:H the current is ∼1×10−4A/cm2. As the temperature of the SiO2deposition is reduced to 150°C the current density rises by up to two orders of magnitude more. The H which is suspected to cause the leakage current across the PECVD oxide originates from the nc-Si:H substrate and the SiH4source gas. We analyzed the 300-nm gate oxide in capacitor structures of Al / SiO2/n+nc-Si:H / Cr / glass, Al / SiO2/ n+nc-Si:H / x-Si, and Al / SiO2/ x-Si. Vacuum annealing the nc-Si:H prior to PECVD of the oxide drives H out of the nc-Si:H film and reduces the amount of H incorporated into the oxide that is deposited on top. SiO2film deposition from SiH4and N2O at high He dilution has a still greater effect on lowering NH. The leakage current at a 10 V bias dropped from ∼1×10−4A/cm2to about ∼2×10−6A/cm2using He dilution at 250°C, and the vacuum anneal of the nc-Si:H lowered it by an additional factor of two. Thus we observe that both the nc-Si:H anneal and the SiO2deposition at high He dilution lessen the gate leakage current.

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.

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