SiOx luminescence from light‐emitting porous silicon: Support for the quantum confinement/luminescence center model

AbstractThrough a comparative study of the light emission and light excitation property of porous silicon (PS) and Si oxide, photoluminescence (PL) and photoluminescence excitation (PLE) mechanisms for blue-light-emitting PS are analyzed. Strong blue light (445nm) and ultraviolet light (365nm) emission from silicon-rich silicon oxynitride films at room temperature were observed. An analysis of the PL and PLE spectra of PS and Si oxide indicated that for blue-light emission from PS, there are two types of photoexcitation processes: photo-excitation occurring in nanometer Si particles (NSP's) and in the Si oxide layers covering NSPs, and radiative recombination of electron-hole pairs taking place in luminescence centers (LCs) located on the interfaces between NSP's and Si oxide and those inside Si oxide layers. The PL spectra of silicon-rich silicon oxynitride films implies that the PL originated from some LCs in SiOx and SiOxNy:H, while PLE spectra indicates that photoexcitation occurs in NSPs, SiOx and SiOxNy:H. The 365 nm band is attributed to the former two photoexcitation processes and the 445 nm one to the third process. As such, the quantum confinement/luminescence center model appears to be a satisfactory model in explaining the experimental results.

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Optical Studies of Electroluminescent Structures from Porous Silicon

MRS Proceedings ◽

10.1557/proc-283-395 ◽

1992 ◽

Vol 283 ◽

Cited By ~ 4

Author(s):

J. F. Harvey ◽

R. A. Lux ◽

D. C. Morton ◽

G. F. McLane ◽

R. Tsu

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Room Temperature ◽

Light Emitting Diode ◽

Spectral Peak ◽

Electrical Excitation ◽

Silicon Structure ◽

Electrical Measurements ◽

Optical Studies ◽

Light Emitting

ABSTRACTTwo components of the electroluminescence (EL) from porous silicon light emitting diode (LED) devices have been observed. A slower component and a faster component have been identified. The slower component has a spectral peak shifted to the red from the corresponding photoluminescence (PL) spectrum. The faster component has a spectral peak well in the infrared (IR). Optical and electrical measurements of these two components are discussed. The temperature dependence of the two EL components are presented and contrasted. Our measurements demonstrate that the two EL components and the PL result from recombination in different parts of the porous silicon structure. As the temperature is reduced below room temperature the slower EL exhibits a decrease in intensity at relatively high temperatures, suggesting a freeze out of electrical carriers due to quantum confinement, resulting in a much reduced electrical excitation of the EL.

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Light-Emitting Porous Silicon in High Magnetic Fields

MRS Proceedings ◽

10.1557/proc-256-59 ◽

1991 ◽

Vol 256 ◽

Cited By ~ 1

Author(s):

X. L. Zheng ◽

H. C. Chen ◽

W. Wang ◽

D. Heiman

Keyword(s):

Magnetic Field ◽

Porous Silicon ◽

Magnetic Fields ◽

Conduction Electron ◽

Quantum Confinement ◽

Major Effect ◽

Spectral Peak ◽

High Magnetic Fields ◽

Helium Atmosphere ◽

Light Emitting

ABSTRACTPhotoluminescence from porous silicon was studied in a helium atmosphere and at high magnetic fields. In a magnetic field, the spectral peak had a negligible shift, amounting to +0.2 ±0.5 meV at B= 18T. If quantum confinement is the major effect, then the conduction electron would be confined to a diameter of less than 3.5 nm.

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Can Oxidation and Other Treatments Help Us Understand the Nature of Light-Emitting Porous Silicon?

MRS Proceedings ◽

10.1557/proc-298-271 ◽

1993 ◽

Vol 298 ◽

Cited By ~ 22

Author(s):

P.M. Fauchet ◽

E. Ettedgui ◽

A. Raisanen ◽

L.J. Brillson ◽

F. Seiferth ◽

...

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Room Temperature ◽

Vacuum Annealing ◽

Surface States ◽

Careful Analysis ◽

Experimental Results ◽

Dangling Bonds ◽

Light Emitting ◽

Confinement Model

AbstractUsing a careful analysis of the properties of light-emitting porous silicon (LEpSi), we conclude that a version of the “smart” quantum confinement model which was first proposed by F. Koch et al [Mat. Res. Soc. Symp. Proc. 283, 197 (1993)] and allows for the existence of surface states and dangling bonds, is compatible with experimental results. Among the new results we present in support of this model, the most striking ones concern the strong infrared photoluminescence that dominates the room temperature cw spectrum after vacuum annealing above 600 K.

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Visible Luminescence from Silicon: Quantum Confinement or Siloxene?

MRS Proceedings ◽

10.1557/proc-262-849 ◽

1992 ◽

Vol 262 ◽

Cited By ~ 5

Author(s):

M. S. Brandt ◽

H. D. Fuchs ◽

A. Höpner ◽

M. Rosenbauer ◽

M. Stutzmann ◽

...

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Alternative Explanation ◽

Present Model ◽

Light Emitting ◽

Light Emitting Devices ◽

Visible Luminescence ◽

Amorphous Si ◽

Silicon Based ◽

Raman And Ir Spectroscopy

ABSTRACTThe discovery of strong visible photoluminescence at room temperature from porous silicon has triggered new hope that light-emitting devices compatible with existing Si-technology might become possible. We first review the luminescence behavior observed in silicon-based materials such as amorphous Si, microcrystalline Si, or SiO2. We then critically discuss the present model for the luminescence from porous silicon based on quantum confinement in view of the growing experimental evidence for the importance of both hydrogen and oxygen to obtain efficient luminescence from this material. We propose an alternative explanation based on the presence of siloxene (SieO3H6) in porous silicon which is corroborated by experimental results obtained with photoluminescence, Raman and IR spectroscopy. An important aspect is that siloxene can be prepared by methods different from anodic oxidation, and one particular technique will be described together with possible ways to tune the luminescence energy.

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Extended quantum confinement/luminescence center model for photoluminescence from oxidized porous silicon and nanometer-si-particle- or nanometer-ge-particle-embedded silicon oxide films

Materials Research Bulletin ◽

10.1016/s0025-5408(98)00182-2 ◽

1998 ◽

Vol 33 (12) ◽

pp. 1857-1866 ◽

Cited By ~ 20

Author(s):

G.G. Qin

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Silicon Oxide ◽

Luminescence Center ◽

Oxide Films ◽

Oxidized Porous Silicon

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New Results on Electroluminescence from Porous Silicon

MRS Proceedings ◽

10.1557/proc-283-343 ◽

1992 ◽

Vol 283 ◽

Cited By ~ 22

Author(s):

Peter Steiner ◽

Frank Kozlowski ◽

Hermann Sandmaier ◽

Walter Lang

Keyword(s):

Porous Silicon ◽

Quantum Efficiency ◽

Light Emitting Diodes ◽

Uv Light ◽

Green Light ◽

Light Emitting ◽

Porous Region ◽

First Results

ABSTRACTFirst results on light emitting diodes in porous silicon were reported in 1991. They showed a quantum efficiency of 10-7 to 10-5 and an orange spectrum. Over the last year some progress was achieved:- By applying UV-light during the etching blue and green light emitting diodes in porous silicon are fabricated.- When a p/n junction is realized within the porous region, a quantum efficiency of 10-4 is obtained.

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Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

MRS Proceedings ◽

10.1557/proc-283-437 ◽

1992 ◽

Vol 283 ◽

Cited By ~ 24

Author(s):

R. Tsu ◽

L. Ioriatti ◽

J. F. Harvey ◽

H. Shen ◽

R. A. Lux

Keyword(s):

Dielectric Constant ◽

Porous Silicon ◽

Size Effects ◽

Quantum Confinement ◽

Electrochemical Etching ◽

Index Of Refraction ◽

Quantum Size Effects ◽

Quantum Size ◽

Quantum Confinement Effects ◽

Shallow Impurities

ABSTRACTThe reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.

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LUMINESCENCE BEHAVIOR AND MECHANISM OF LIGHT-EMITTING POROUS SILICON

Modern Physics Letters B ◽

10.1142/s021798499400008x ◽

1994 ◽

Vol 08 (02) ◽

pp. 69-92 ◽

Cited By ~ 5

Author(s):

XUN WANG

Keyword(s):

Porous Silicon ◽

Blue Light ◽

Light Emission ◽

Energy State ◽

Surface Recombination Velocity ◽

Luminescence Spectroscopy ◽

Carrier Injection ◽

Blue Light Emission ◽

Light Emitting ◽

Si Nanostructures

In this review article, we give a new insight into the luminescence mechanism of porous silicon. First, we observed a “pinning” characteristic of photoluminescent peaks for as-etched porous silicon samples. It was explained as resulting from the discontinuous variation of the size of Si nanostructures, i.e. the size quantization. A tight-binding calculation of the energy band gap widening versus the dimension of nanoscale Si based on the closed-shell Si cluster model agrees well with the experimental observations. Second, the blue-light emission from porous silicon was achieved by using boiling water treatment. By investigating the luminescence micrographic images and the decaying behaviors of PL spectra, it has been shown that the blue-light emission is believed to be originated from the porous silicon skeleton rather than the surface contaminations. The conditions for achieving blue light need proper size of Si nanostructures, low-surface recombination velocity, and mechanically strong skeleton. The fulfillment of these conditions simultaneously is possible but rather critical. Third, the exciton dynamics in light-emitting porous silicon is studied by using the temperature-dependent and picosecond time-resolved luminescence spectroscopy. A direct evidence of the existence of confined excitons induced by the quantum size effect has been revealed. Two excitation states are found to be responsible for the visible light emission, i.e. a higher lying energy state corresponding to the confined excitons in Si nanostructures and a lower lying state related with surfaces of Si wires or dots. A picture of the carrier transfer between the quantum confined state and the surface localized state has been proposed. Finally, we investigated the transient electroluminescence behaviors of Au/porous silicon/Si/Al structure and found it is very similar to that of an ordinary p-n junction light-emitting diode. The mechanism of electroluminescence is explained as the carrier injection through the Au/porous silicon Schotky barrier and the porous silicon/p-Si heterojunction into the corrugated Si wires, where the radiative recombination of carriers occurs.

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Depth-Resolved Microspectroscopy of Porous Silicon Multilayers

MRS Proceedings ◽

10.1557/proc-588-155 ◽

1999 ◽

Vol 588 ◽

Author(s):

S. Manotas ◽

F. Agulló-Rueda ◽

J. D. Moreno ◽

R. J. Martín-Palma ◽

R. Guerrero-Lemus ◽

...

Keyword(s):

Porous Silicon ◽

Quantum Confinement ◽

Silicon Nanocrystals ◽

Phonon Frequency ◽

Lattice Mismatch ◽

High Porosity ◽

Phonon Confinement ◽

Heating Effects ◽

Average Size ◽

Good Agreement

AbstractWe have measured micro-photoluminescence (PL) and micro-Raman spectra on the cross section of porous silicon multilayers to sample different layer depths. We find noticeable differences in the spectra of layers with different porosity, as expected from the quantum confinement of electrons and phonons in silicon nanocrystals with different average sizes. The PL emission band gets stronger, blue shifts, and narrows at the high porosity layers. The average size can be estimated from the shift. The Raman phonon band at 520 cm−1 weakens and broadens asymmetrically towards the low energy side. The line shape can be related quantitatively with the average size by the phonon confinement model. To get a good agreement with the model we add a band at around 480 cm−1, which has been attributed to amorphous silicon. We also have to leave as free parameters the bulk silicon phonon frequency and its line width, which depend on temperature and stress. We reduced laser power to eliminate heating effects. Then we use the change of frequency with depth to monitor the stress. At the interface with the substrate we find a compressive stress in excess of 10 kbar, which agrees with the reported lattice mismatch. Finally, average sizes are larger than those estimated from PL.

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