Influence of Different Atmospheres on the Life Time of Porous Silicon Light-Emitting Devices

2002 ◽  
Vol 737 ◽  
Author(s):  
B.R. Jumayev ◽  
H.L. Tam ◽  
K.W. Cheah ◽  
N.E. Korsunska
Keyword(s):  
Porous Silicon ◽  
Reverse Bias ◽  
Present Report ◽  
Forward Bias ◽  
Life Time ◽  
Visible Range ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Cu Alloy ◽  
Metal Diffusion

ABSTRACTIn present report, we investigated the degradation processes in porous silicon light-emitting devices (LED) in different atmospheres (O2, N2, air and vacuum) by photoluminescence (PL), electroluminescence (EL), lifetime (LT) and I-V characteristic measurements as well as by Energy Dispersive X-ray Spectroscopy (EDS). The contacts were made by evaporation of Au and Au/Cu alloy. The LEDs emit in visible range at forward and reverse bias. As a rule, full width at half maximum of EL spectrum is wider than that of PL spectrum. The bias direction of applied voltage during degradation change EL, PL, I-V characteristics, and LT of the LEDs. At forward bias, LT degradation is less than that in reverse bias.The degradation of LEDs during forward bias did not produce any change in the spectral shape of EL and PL. At reverse bias, degradation led to red shift in the peak of EL and PL. The results show that the lifetime of LEDs with Au contact is longer than Au-Cu. Operating in different atmospheres, the LT in vacuum is longest and is more than 100 hours in reverse bias at room temperature.Possible mechanisms of degradation of LEDs are discussed. It is proposed that degradation is connected mainly with two processes: oxidation and metal diffusion. It is shown that the oxygen and metal in ionic state can diffuse quickly. Hence, in forward bias, the diffusion of metal would dominate, and in reverse bias, diffusion of oxygen dominates.

Visible Electroluminescence from Al-Porous Silicon Reverse Bias Diodes Formed on the Base of Degenerate N-Type Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
S. Lazarouk ◽  
V. Bondarenko ◽  
P. Pershukevich ◽  
S. La Monica ◽  
G. Maiello ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Reverse Bias ◽  
Light Emission ◽  
Electrochemical Etching ◽  
Forward Bias ◽  
Applied Bias ◽  
Light Emitting ◽  
Type Silicon ◽  
Silicon Devices ◽  
Preparation Conditions

ABSTRACTWe demonstrate current induced visible light emission from Schottky junctions between aluminium electrodes and porous silicon formed by electrochemical etching of degenerate n+ -type silicon. HF concentration and anodizing current were chosen to yield preparation conditions in the transition region between electropolishing and porous silicon formation regimes. The light emitting diodes were formed by magnetron sputtering of aluminum on the porous silicon surface. Visible electroluminescence (EL) was recorded when dc or ac voltages larger than 4 V were applied between the aluminium electrodes. The visible EL appears in the dark, at the edge of the electrodes at a reverse bias of 5-6 V. The intensity of emitted light increases with applied voltage; at applied bias higher than 7 V the light emitted was observable by the naked eye at normal daylight. Compared to forward bias solid state contact porous silicon devices, the structure has an increased stability (after 100 hours of continuous operation under a 7 V reverse bias, no appreciable modification was observed in emission intensity). The main features of this electroluminescence are very similar to the ones observed under avalanche breakdown of silicon p-n junctions.

A New Prediction Model on the Luminance of OLEDs Subjected to Different Reverse Biases for Alleviating Degradation in AMOLED Displays

2014 ◽  
Author(s):  
Paul C.-P. Chao ◽  
Yen-Ping Hsu ◽  
Yung-Hua Kao ◽  
Kuei-Yu Lee
Keyword(s):  
Reverse Bias ◽  
High Efficiency ◽  
Life Time ◽  
Density Currents ◽  
High Brightness ◽  
Light Emitting ◽  
Wide Viewing Angle ◽  
Time Operation ◽  
Long Time ◽  
History Of

Organic light-emitting diodes (OLEDs) have drawn much attention in areas of displays and varied illumination devices due to multiple advantages, such as high brightness, high efficiency, wide viewing angle, and simple structure. However, the long-time degradation of OLED emission is a serious drawback. This degradation was investigated by past works, which pointed out that the degradation was induced by high-density currents through OLED component under the long-time operation [1][2]. Proposed by a past work [3], different reverse biases was imposed on OLED components in display frames to alleviate the long-time degradation on OLEDs. Most recently, along with the reverse bias, new pixel circuits [4][5] for AMOLED displays are designed to alleviate OLED degradation, thus successfully extending OLED life time. However, since emission luminances in different frame times during AMOLED displaying differs significantly for displaying varied images, the OLED degradation evolves in a highly unpredictable fashion. In this study, based on valid theories, the voltage across the OLED is first used as indicator for OLED degradation. Then the relation between the level of OLED degradation, in terms of OLED’s cross voltage, and the history of imposing reverse biases are precisely modeled. With the model, the degradation of the OLED under reverse bias to extend lifetime can be successfully predicted. Based on this model, engineers can then optimize the applied reverse bias on OLEDs to maximize the OLED lifetime for varied display requirement.

New Structures and Materials for Next Generation Photonic Technology

2011 ◽  
Vol 120 ◽  
pp. 556-560
Author(s):  
D. H Zhang ◽  
T. Mei ◽  
D.Y. Tang ◽  
X. C. Yuan ◽  
T. P. Chen
Keyword(s):  
Light Source ◽  
Silicon On Insulator ◽  
Visible Range ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Light Manipulation ◽  
Loss Compensation ◽  
Photonic Circuit ◽  
Nano Crystal ◽  
First Time

We present the main results achieved in light source, light manipulation and imaging and sensing in our competitive research program. In light source, we have for the first time developed grapheme mode-locked lasers and dark pause lasers as well as nano-crystal Si based light emitting devices with colour tunable. In light manipulation, loss compensation of surface plasmon polaritons (SPPs) using semiconductor gain media was studied theoretically and demonstrated experimentally and the SPP propagation can be controlled through electrical pumping. Microring resonators based on silicon on insulator and III-V semiconductors technologies have been successfully fabricated and they can be used as filter and switch in the photonic circuit. In imaging and sensing, both SPP and metamaterial based lenses are developed and resolution far beyond diffraction limit in visible range has been realized. Broadband photodetectors based on dilute nitrides are also demonstrated.

Light emitting devices using poly (p-phenylene vinylene)/porous silicon composites

2001 ◽  
Vol 121 (1-3) ◽  
pp. 1631-1632 ◽  
Author(s):  
M. Lakehal ◽  
T.P. Nguyen ◽  
P. Le Rendu ◽  
P. Joubert ◽  
P. Destruel
Keyword(s):  
Porous Silicon ◽  
Phenylene Vinylene ◽  
Light Emitting ◽  
Light Emitting Devices

Effect of Electrolyte Volume Ratio on Electroluminescence of Porous Silicon Nanostructures (PSiNs) Intensity

2013 ◽  
Vol 686 ◽  
pp. 49-55
Author(s):  
M. Ain Zubaidah ◽  
N.A. Asli ◽  
Mohamad Rusop ◽  
Saifollah Abdullah
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Light Emitting Diode ◽  
Volume Ratio ◽  
Visible Range ◽  
Silicon Nanostructures ◽  
Etching Time ◽  
Light Emitting ◽  
Flat Screen ◽  
P Type

For this experiment, the main purpose of this experiment is to determine the electroluminescence of PSiNs samples with optimum electrolyte volume ratio of photo-electrochemical anodisation. PSiNs samples were prepared by photo-electrochemical anodisation by using p-type silicon substrate. For the formation of PSiNs on the silicon surface, a fixed current density (J=20 mA/cm2) and 30 minutes etching time were applied for the various electrolyte volume ratio. Volume ratio of hydrofluoric acid 48% (HF48%) and absolute ethanol (C2H5OH), HF48%:C2H5OH was used for sample A (3:1), sample B (2:1), sample C (1:1), sample D (1:2) and sample E (1:3). The light emission can be observed at visible range. The effective electroluminescence was observed for sample C. Porous silicon nanostructures light–emitting diode (PSiNs-LED) has high-potential device for future flat screen display and can be high in demand.

ZnO Nanowire/p-GaN Heterojunction LEDs

2007 ◽  
Vol 1018 ◽  
Author(s):  
Heiko O. Jacobs ◽  
Jesse Cole ◽  
Amir M. Dabiran ◽  
Heiko O. Jacobs
Keyword(s):  
Reverse Bias ◽  
Forward Bias ◽  
Zno Nanowires ◽  
Hole Injection ◽  
Zno Nanowire ◽  
Defect States ◽  
Light Emitting ◽  
Current Voltage ◽  
Distinct Color ◽  
Two Peaks

AbstractThis article reports forward and reverse biased emission in vertical ZnO nanowire/p-GaN heterojunction light emitting diodes (LEDs) grown out of solution on Mg-doped p-GaN films. The electroluminescence spectra under forward and reverse bias are distinctly different. Forward bias showed two peaks centered around 390 nm and 585 nm, while reverse bias showed a single peak at 510 nm. Analysis of the current-voltage characteristics and electroluminescence spectra is presented to determine the transport mechanism and location of electron hole recombination. Reverse bias transport and luminescence are attributed to hot-hole injection from the ZnO nanowires into the GaN film through tunneling breakdown. Forward bias transport and luminescence are attributed to hole injection from the GaN into the ZnO and recombination at defect states inside the ZnO yielding distinct color variations between individual wires. Major resistive losses occurred in the GaN lateral thin film connecting to the vertical ZnO nanowires.

Theory of Porous Silicon Injection Electroluminescence

1992 ◽  
Vol 283 ◽  
Author(s):  
H. Paul Maruska ◽  
F. Namavar ◽  
N. M. Kalkhoran
Keyword(s):  
Porous Silicon ◽  
Light Emission ◽  
Forward Bias ◽  
Interface States ◽  
Light Emitting ◽  
Long Term Stability ◽  
Quantum Confinement Effects ◽  
Current Path ◽  
Yellow Orange ◽  
P Type

ABSTRACTWe discuss the operation of porous silicon light-emitting diodes prepared as heterojunctions between n-type In2O3:Sn (ITO) and p-type silicon nanostructures, exhibiting quantum confinement effects. The transparent ITO affords light emission through the top surface of the device, as well as providing passivation and hence long term stability. We describe a model for the injection of minority carrier electrons into the porous silicon regions, which results in the emission of yellow-orange DC electroluminescence. A detailed study of the forward bias current-voltage characteristics of the devices will be given, which allows calculations of the densities of interface states. A tendency to pin the hole fermi energy near the neutral level, φ0, is shown to control the extraction of majority carriers. Methods for improving LED efficiency by alleviating a parasitic shunt current path through interface states will be addressed.

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