Alternative Mechanism for Defect Generation in a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
David Redfield
Keyword(s):  
Energy Barrier ◽  
Recombination Event ◽  
Reverse Bias ◽  
Defect Formation ◽  
Forward Bias ◽  
Alternative Mechanism ◽  
Defect Centers ◽  
Induced Changes ◽  
Configuration Coordinate ◽  
Configuration Coordinate Diagram

ABSTRACTRecombination-driven mechanisms for defect formation do not account well for several experimental facts, and indeed conflict with some facts. To overcome these problems, an alternative mechanism is proposed in which latent defect centers are converted to metastable defects (dangling bonds) without a recombination event. The transitions are driven simply by electron capture at the center with no energy barrier. A new configuration-coordinate diagram expressing this mechanism includes essential configuration-induced changes in the energies of band edges, and accounts for several other previously problematic observations. This carrier-induced mechanism (CIM) is consistent with defect formation in forward bias and defect inhibition in reverse bias, light-enhanced annealing, as well as the usual light-induced and beam-induced formation. For low orħħωthe process starts by ionization of an existing defect.

Response Time of a-Si:H Photosensors in Optically Addressed Spatial Light Modulators

1991 ◽  
Vol 219 ◽  
Author(s):  
Garret Moddel ◽  
Pierre R. Barbier
Keyword(s):  
Liquid Crystal ◽  
Response Time ◽  
Spatial Light Modulator ◽  
Reverse Bias ◽  
Forward Bias ◽  
Spatial Light Modulators ◽  
Photocurrent Response ◽  
Light Modulator ◽  
Double Injection ◽  
Light Modulators

ABSTRACTA successful application for a-Si:H is as the photosensor in a liquid crystal optically addressed spatial light modulator (OASLM). We analyze the response time of an a-Si:H p-i-n photodiode in a “pseudo-OALSM,” in which the liquid crystal is replaced by an equivalent capacitor, under both forward and reverse bias. Under reverse bias the two important effects are the photocurrent response time, and residual trapped charge. Under forward bias the mechanism shifts from double injection regimes to ohmic transport as a function of voltage. We relate these characteristics to the operation of an OASLM.

Molecular Photodiode and Two-channel Optoelectronic Demultiplexer based on the [60]Fullerene-porphyrin Tetrad

2011 ◽  
Vol 64 (10) ◽  
pp. 1409 ◽  
Author(s):  
Kornelia Lewandowska ◽  
Konrad Szaciłowski
Keyword(s):  
Absorption Spectrum ◽  
High Intensity ◽  
Reverse Bias ◽  
Forward Bias ◽  
Bias Current ◽  
Switching Effect ◽  
Negative Polarization ◽  
Current Ratio ◽  
Substrate Potential ◽  
Positive Polarization

Photoelectrodes containing Langmuir–Blodget layers of [60]fullerene-porphyrin tetrad behave like photodiodes. Upon excitation within the whole absorption spectrum of the molecule they generate photocurrent, the direction of which depends on the conducting substrate potential. At negative polarization high intensity cathodic photocurrent are observed, while at positive polarization much weaker anodic photocurrents are observed. The forward-bias to reverse-bias current ratio amounts 5:1. Therefore the [60]fullerene-porphyrin tetrad is closely related to semiconductors showing photoelectrochemical photocurrent switching effect and is a promising material for molecular optoelectronics. It can be used as a simple molecular photodiode. Assignment of logic values to polarization of the photoelectrode and to light and photocurrent pulses results in a very efficient two-channel optoelectronic demultiplexer.

Role of Interface-States in the Reverse Bias Aging of GaAs Schottky Barriers

1990 ◽  
Vol 184 ◽  
Author(s):  
K. A. Christianson
Keyword(s):  
Cross Section ◽  
Aging Process ◽  
Reverse Bias ◽  
Capture Cross Section ◽  
Forward Bias ◽  
Interface State ◽  
Schottky Barriers ◽  
Capture Cross ◽  
State Generation ◽  
Thermionic Field Emission

ABSTRACTForward bias capacitance has been used to examine the Au/W/GaAs and Au/Pt/Ti/GaAs Schottky barriers present in power microwave MESFET devices to see if interface-state generation plays any role in the previously reported reverse bias barrier height aging process. If a constant carrier capture cross-section is assumed, forward bias capacitance has shown that for samples strongly susceptible to aging (i.e. the Au/W/GaAs samples in this study) interface-state generation is taking place during the aging process. The validity of the constant capture cross section assumption has been tested by examining the I–V properties. For those samples whose reverse I–V properties were not dominated by thermionic-field emission, similar increases in interface-state densities were evaluated from the I–V characteristics for the degraded samples.

Photoresponse of Zinc Oxide-Polyaniline Junction at Different Light Intensities

2016 ◽  
Vol 705 ◽  
pp. 186-189 ◽  
Author(s):  
Everjoy S. Mones ◽  
Armida V. Gillado ◽  
Marvin U. Herrera
Keyword(s):  
Zinc Oxide ◽  
Light Intensity ◽  
Reverse Bias ◽  
Electronic Devices ◽  
Forward Bias ◽  
Bias Current ◽  
Oxide Semiconductor ◽  
Light Intensities ◽  
Promising Application ◽  
Doped Polyaniline

Polymer-oxide semiconductor exhibits a promising application on electronic devices. In this study, zinc oxide-polyaniline (ZnO-PAni) junctions were constructed which showed a photodiode-like behavior. The junctions were built through connecting the electrodeposited zinc oxide to electrodeposited HCl-doped polyaniline. Without illumination, the junctions exemplify a diode-like behavior (e.g., large amount current at forward-bias while small amount of current at reverse-bias). When illuminated, the junctions exhibit a photodiode-like behavior. In such, the reverse-bias current increases with light intensity.

A Comparative Study Of GaN Diodes Grown by MBE on Sapphire and HVPE-GaN /Sapphire Substrates

1999 ◽  
Vol 595 ◽  
Author(s):  
Anand V. Sampath ◽  
Mira Misra ◽  
Kshitij Seth ◽  
Yuri. Fedyunin ◽  
Hock M. Ng ◽  
...  
Keyword(s):  
Comparative Study ◽  
Reverse Bias ◽  
Schottky Diodes ◽  
Forward Bias ◽  
Etch Pits ◽  
Sapphire Substrates ◽  
Fabrication And Characterization

AbstractIn this paper we report on the fabrication and characterization of GaN diodes (Schottky and p-n junctions) grown by plasma assisted MBE. We observed that Schottky diodes improve both in reverse as well as forward bias when deposited on 5 μm thick HVPE n+-GaN/sapphire instead of bare sapphire substrates. These improvements are attributed to the reduction of disloctions in the MBE homoepitaxially grown GaN. Similar benefits are observed in the reverse bias of the p-n junctions which according to EBIC measurements are attributed to the reduction of etch pits in the MBE grown p-GaN.

Heteroepitaxy on (001) Silicon: Growth Mechanisms and Defect Formation.

1988 ◽  
Vol 116 ◽  
Author(s):  
P. Pirouz ◽  
F. Ernst ◽  
T. T. Cheng
Keyword(s):  
Defect Formation ◽  
Lattice Mismatch ◽  
Minor Role ◽  
Alternative Mechanism ◽  
Growth Mechanisms ◽  
Planar Defects ◽  
Step Process ◽  
One Step ◽  
The One ◽  
A Minor

AbstractIn the growth of thin films of compound semiconductors on (001) silicon substrates by vapor deposition techniques, it is usual to employ a two-step process. In this method, an initial (buffer) layer is first grown at a relatively low temperature; once a continuous film has formed on the substrate, its temperature is raised for the subsequent bulk growth. Carrying out the growth in a one-step process by heating the substrate to the final temperature before allowing the gases into the CVD reactor usually results in a polycrystalline aggregate. In this paper, classical nucleation and growth mechanisms are used to explain-the reasons for the different morphology of the one-step and two-step growth films.The heteroepitaxial films on (001) silicon often contain a high density of stacking faults and twins. The occurrence of these planar defects is usually attributed to stresses that arise from lattice mismatch and/or thermal mismatch (differences in coefficients of thermal expansion) between the substrate and the epilayer. It is argued that, in fact, mismatch stresses play a minor role in the generation of planar defects. Instead, an alternative mechanism for their formation is proposed which is based on the facetted shape of nuclei and errors in stacking of {111} planes which occur during deposition on the facets.Conventional and high resolution transmission electron microscopy have been used to investigate three systems grown by CVD or MOCVD: SiC/Si, GaAs/Si and GaP/Si. These systems have different lattice and thermal mismatches, and the results support the proposed model for the formation of defects.

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