Excitation Mechanisms and Light Emitting Device Performances in Er-Doped Crystalline Si

1996 ◽  
Vol 422 ◽  
Author(s):  
F. Priolo ◽  
S. Coffa ◽  
G. Franzo ◽  
A. Polman
Keyword(s):  
Reverse Bias ◽  
Crystalline Silicon ◽  
Forward Bias ◽  
Depletion Region ◽  
Impact Excitation ◽  
Electron Hole ◽  
Light Emitting ◽  
Temperature Operating ◽  
Excitation Mechanisms ◽  
Er Doped

AbstractIn this paper the performances of room temperature operating light emitting diodes (LEDs), fabricated by Er ion implantation of crystalline silicon, are investigated in detail. It is shown that 1.54 μm emission is observed under both forward and reverse bias operation, with a much higher intensity under reverse bias. The excitation mechanisms of Er3+ are demonstrated to be very different in the two cases: under forward bias Er is excited through the electron - hole recombination at an Er - related level, while under reverse bias impact excitation by hot carriers represents the excitation process. This last mechanism is shown to occur with a cross section of 6 × 10−17 cm2 and population inversion of the excitable Er sites within the depletion region is demonstrated. The efficiency and limitations of this approach are also discussed.

Impact Excitation And Auger Quenching Processes In Er Doped Light Emitting Si Devices

1997 ◽  
Vol 486 ◽  
Author(s):  
G. Franzo' ◽  
F. Priolo ◽  
S. Coffa
Keyword(s):  
High Efficiency ◽  
Depletion Region ◽  
Light Signal ◽  
Impact Excitation ◽  
Light Emitting ◽  
Free Carriers ◽  
Heavily Doped ◽  
Excitation Processes ◽  
Er Doped ◽  
Incorporation Method

AbstractA detailed investigation of the Auger non radiative de-excitation processes, which compete with the radiative emission of Er in Si, will be presented. This process, in which the energy released by the Er de-excitation is transferred to free carriers, is demonstrated to be extremely efficient and characterized by an Auger coefficient CA˜4.4×l0−13 cm3/s. This Auger process and an efficient incorporation method have been used to improve the performances of Er implanted light emitting diodes. It will be shown that by exciting Er within the depletion region of reverse biased p+-n+ Si diodes in the breakdown regime, it is possible to avoid Auger quenching and to achieve high efficiency. Moreover, at the switch off of the diode, when the depletion region shrinks, the excited Er ions become suddenly embedded within the neutral heavily doped region. In this region Auger de-excitation with free carriers sets in allowing to modulate the light signal at frequencies as high as a few MHz.

Effect of the Hetero-Interface on the Photoresponse of A-Si/C-Si Solar Cells

1994 ◽  
Vol 358 ◽  
Author(s):  
B. Jagannathan ◽  
J. Yi ◽  
R. Wallace ◽  
W. A. Anderson
Keyword(s):  
Solar Cells ◽  
Crystalline Silicon ◽  
Spectral Response ◽  
Forward Bias ◽  
Depletion Region ◽  
Defect States ◽  
Heterojunction Solar Cells ◽  
Si Solar Cells ◽  
Wavelength Absorption ◽  
P Type

ABSTRACTHeterojunction solar cells were fabricated by glow discharge deposition of amorphous silicon on p-type crystalline silicon resulting in a n/i/p structure. Dark I-V-T data on the devices show that the conduction in the forward bias regime (<0.4 volts) for better devices agrees with a multi-tunnelling-capture-emission process. The photoresponse was evaluated (under 100 mW/cm2) for various a-Si thicknesses and substrate resistivities. Spectral response tests showed an increased low wavelength absorption as the a-Si thickness was decreased. The blue response of the devices have better fill-factors than the red response indicating defects at the interface. Further, I-V-T and C-V measurements also corroborate the presence of defect states which seem to prevent the spread of the depletion region in crystalline silicon. The photoresponse was found to be very sensitive to the interface defects and the fill-factors ranged from 0.42, for the sample in which the depletion region had spread, to 0.1 in those where the depletion region had been reduced in thickness by the interface states.

A Led Based on Porous Polycrystalline Silicon

1997 ◽  
Vol 486 ◽  
Author(s):  
W. N. Huang ◽  
K. Y. Tong ◽  
P. W. Chan
Keyword(s):  
Silicon Substrate ◽  
Polycrystalline Silicon ◽  
Polycrystalline Material ◽  
Forward Bias ◽  
Depletion Region ◽  
Silicon Substrates ◽  
Large Area ◽  
Electron Hole ◽  
Bright Spots ◽  
Current Characteristics

AbstractPrevious studies on electroluminescence in porous silicon were based on crystalline wafers. In this paper, we shall report the characteristics of a LED based on porous effects in a cast polycrystalline silicon substrate. A layer of porous region was first formed on a cast polycrystalline silicon substrate by anodization, followed by the deposition of a semitransparent Au layer. Under forward bias, the LED emits stable yellowish white light (with the presence of bright spots) for currents above 20 mA/cm2. From the electroluminescence spectra measured, we suggest that the emission is due to the recombination of electron-hole pairs in a microplasma region. We propose a model where the microplasma is present in the depletion region of the heterojunction formed between the bulk polysilicon and the surface porous polysilicon. The defects and grain boundaries in a polycrystalline material facilitate the formation of such microplasma. The heterojunction model will also be used to explain the current characteristics of the LED. The effect on the LED characteristics due to indium coating on the porous substrate prior to Au deposition was studied, and the results agree with the heterojunction model. Our work shows that cast polycrystalline silicon substrates have potential for LED fabrication in cheap and large area applications.

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.

scholarly journals Visible and Infrared Rare-Earth Activated Electroluminescence from Erbium Doped GaN

1999 ◽  
Vol 4 (S1) ◽  
pp. 940-945 ◽  
Author(s):  
M. Garter ◽  
R. Birkhahn ◽  
A. J. Steckl ◽  
J. Scofield
Keyword(s):  
Indium Tin Oxide ◽  
Ground State ◽  
Reverse Bias ◽  
Light Emission ◽  
Forward Bias ◽  
Bias Current ◽  
Emission Lines ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Ir Light

Room temperature visible and IR light electroluminescence (EL) has been obtained from Er-doped GaN Schottky barrier diodes. The GaN was grown by molecular beam epitaxy on Si substrates using solid sources (for Ga and Er) and a plasma source for N2. Transparent contacts utilizing indium tin oxide were employed. Strong green light emission was observed under reverse bias due to electron impact excitation of the Er atoms. Weaker emission was present under forward bias. The emission spectrum consists of two narrow green lines at 537 and 558 nm and minor peaks at 413, 461, 665, and 706 nm. There is also emission at 1000 nm and 1540 nm in the IR. The green emission lines have been identified as Er transitions from the 2H11/2 and 4S3/2 levels to the 4I15/2 ground state. The IR emission lines have been identified as transitions from the 4I11/2 and 4I13/2 levels to the 4I15/2 ground state. EL intensity for visible and IR light has a sub-unity power law dependence on bias current. An external quantum efficiency of 0.1% has also been demonstrated under a reverse bias current of 3.85 mA.

Impact excitation of Er-doped GaAs and the rare-earth sites in III-V compound semiconductors

1993 ◽  
Vol 301 ◽  
Author(s):  
S. J. Chang ◽  
K. Takahei ◽  
J. Nakata ◽  
Y. K. Su
Keyword(s):  
Energy Transfer ◽  
Interstitial Site ◽  
Impact Excitation ◽  
Electron Hole ◽  
Pl Spectra ◽  
Gaas Substrates ◽  
Tetrahedral Interstitial Site ◽  
Different Temperatures ◽  
Er Doped ◽  
Hole Recombination

ABSTRACTWe report the first study of impact excitation of Er ions in GaAs. The MOCVDgrown, p+-n structured EL devices were fabricated by growing, at different temperatures, GaAs:Er layers on top of the n+ GaAs substrates. P+ layers were made by Zn diffusion from the top surfaces. When we forward biased these diodes, their EL spectra were similar to their respective PL spectra for each sample but different from each other's. However, when we reverse biased these diodes, EL spectra obtained from all samples are the same, which were different from their PL spectra. These results indicate that the Er center(s) excited by direct impact is different from the Er center(s) excited through electron-hole recombination and subsequent energy transfer. By using RBS channeling, we found that most of the Er ions, in our MOCVD-grown GaAs:Er samples, occupy a displaced tetrahedral interstitial site. From these PL, EL and RBS results, we conclude that only a small amount of Er ions emit luminescence when they are indirectly excited through energy transfer.

The Possible Mechanism of Excitation of the f - f Emission from Er-O Clusters in Silicon

1996 ◽  
Vol 422 ◽  
Author(s):  
V. F. Masterov ◽  
L. G. Gerchikov
Keyword(s):  
Quantum Dot ◽  
Quantum Well ◽  
Forward Bias ◽  
Electron Trap ◽  
Electron Hole ◽  
Electron Level ◽  
Light Emitting ◽  
Trapped Electron ◽  
Hole Recombination

AbstractThe Er2O3 quantum dot (cluster) with dimensions about 1.2nm in silicon is discussed as the possible source of the Er related emission in Si:Er,O, excited by photogenerated carriers or in a light-emitting diodes (LED) at forward bias. This quantum dot is represented as a spherical quantum well 0.9eV in depth. The electron level with energy about 0.15eV below the bottom of the silicon conduction band plays role of an electron trap. The trapped electron interacts with a hole in valence band of silicon forming “indirect” exciton bonded to quantum well. The energy is transferred to f - shell of erbium by the Auger electron - hole recombination.

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.

Control of Light-Emitting Polymer Devices Using Polymer/Polymer Interfaces

1997 ◽  
Vol 488 ◽  
Author(s):  
A. J. Epstein ◽  
Y. Z. Wang ◽  
D. D. Gebler ◽  
D. K. Fu ◽  
T. M. Swager
Keyword(s):  
Reverse Bias ◽  
Forward Bias ◽  
Single Layer ◽  
Hole Transport ◽  
Cathode Side ◽  
Emeraldine Base ◽  
Polymer Interfaces ◽  
Light Emitting ◽  
Polymer Devices ◽  
Control Light

AbstractWe present the use of polymer/polymer interfaces to control light-emitting polymer devices. Bilayer devices utilizing poly(9-vinyl carbazole) (PVK) as a hole transporting/electron blocking polymer together with a pyridine containing electron transporting layer show dramatically improved efficiency and brightness as compared to single layer devices. This is attributed to charge confinement and exciplex emission at the PVK/emitting polymer interface. The introduction of emeraldine base (EB) form of polyaniline (PAN) on both side of the emitting layer enables the device to work under both forward and reverse bias, as well as in AC modes. Interfaces play an important role in the operation of these devices. Furthermore, when the EB is replaced by sulfonated polyaniline (SPAN) on the cathode side and the emitting layer is properly modified to balance electron and hole transport, the device generates different colors of light, red under forward bias and green under reverse bias.

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