Energy Localisation and Surface Interactions in the Luminescence of Porous Silicon

1993 ◽  
Vol 298 ◽  
Author(s):  
S. Gardelis ◽  
P. Dawson ◽  
B. Hamilton
Keyword(s):  
Porous Layer ◽  
Light Emission ◽  
Vacuum Annealing ◽  
Optical Emission ◽  
Radiative Transition ◽  
Material System ◽  
Porous Si ◽  
Lower Energy Band ◽  
Spin Resonance ◽  
Processing Steps

AbstractThe fundamental mechanisms controlling the light emission from porous Si remain unresolved. In this paper we report attempts to modify the luminescence using a variety of surface processing steps, such as vacuum annealing with subsequent anneals in nitrogen and oxygen, exposure to hydrofluoric acid (HF) and rapid thermal oxidation. Luminescence, infrared absorption, and electron spin resonance (ESR) have all been used to gain more information on the link between the optical emission and the localisation of the electrons in this material system. We present evidence that the silicon dangling bond is the key component in the non-radiative recombination. This is based on measurements shown that hydrogen coverage of the surface is significant because of saturation of the dangling bonds and a subsequent reduction in the competing non-radiative paths rather than as an active component in the radiative transition. Finally, we focus our attention upon the lower energy band which appears in the luminescence spectrum of porous Si (∼0.9eV) by examining its behavior under the surface treatments mentioned above. We found that this luminescence band originates from the surface of the porous layer and its intensity correlates well with increasing oxidation of the porous layer.

Investigation Of Efficiency Improvement on Silicon Solar Cells Due to Porous Layers

1994 ◽  
Vol 358 ◽  
Author(s):  
Gregory Sun ◽  
Yuxin Li ◽  
Yicheng Lu ◽  
Babar Khan ◽  
Gary S. Tompa
Keyword(s):  
Solar Cells ◽  
Porous Layer ◽  
Light Emission ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Porous Si ◽  
Etching Technique ◽  
Shallow Junction ◽  
Si Solar Cells

ABSTRACTObservation of light emission from porous Si has demonstrated that the optical properties of Si can be drastically altered by the quantum size effects. We have investigated the improvement of absorption properties of Si material by forming a porous Si layer. Shallow-junction commercial crystalline as well as polycrystalline Si solar cells without anti-reflective coatings have been processed into porous Si solar cells by a wet chemical etching technique. Our best results have demonstrated more than 15% improvement in short-circuit current with no change in open-circuit voltage. The performance of the porous Si solar cells has been found to be sensitive to the porous layer thickness. The efficiency can be reduced when the porous layer is relatively deep, presumably due to the penetration of pores through the shallow junction. We believe porous Si can be optimized for photovoltaic applications by properly controlling its porosity and thickness.

Structural, Surface Morphological and Photoluminescence Properties of Nanostructured Porous Silicon Material for Optoelectronics Application

2012 ◽  
Vol 584 ◽  
pp. 290-294 ◽  
Author(s):  
Jeyaprakash Pandiarajan ◽  
Natarajan Jeyakumaran ◽  
Natarajan Prithivikumaran
Keyword(s):  
Porous Silicon ◽  
Current Density ◽  
Light Emission ◽  
Electrochemical Etching ◽  
Light Emitting Diode ◽  
Radiative Transition ◽  
Sem Images ◽  
Optoelectronic Application ◽  
Gap Opening ◽  
P Type

The promotion of silicon (Si) from being the key material for microelectronics to an interesting material for optoelectronic application is a consequence of the possibility to reduce its device dimensionally by a cheap and easy technique. In fact, electrochemical etching of Si under controlled conditions leads to the formation of nanocrystalline porous silicon (PS) where quantum confinement of photo excited carriers and surface species yield to a band gap opening and an increased radiative transition rate resulting in efficient light emission. In the present study, the nanostructured PS samples were prepared using anodic etching of p-type silicon. The effect of current density on structural and optical properties of PS, has been investigated. XRD studies confirm the presence of silicon nanocrystallites in the PS structure. By increasing the current density, the average estimated values of grain size are found to be decreased. SEM images indicate that the pores are surrounded by a thick columnar network of silicon walls. The observed PL spectra at room temperature for all the current densities confirm the formation of PS structures with nanocrystalline features. PL studies reveal that there is a prominent visible emission peak at 606 nm. The obtained variation of intensity in PL emission may be used for intensity varied light emitting diode applications. These studies confirm that the PS is a versatile material with potential for optoelectronics application.

Photovoltaic and Electroluminescent Properties of Stainetched Porous Silicon Based Heterojunctions

1995 ◽  
Vol 405 ◽  
Author(s):  
D. Dimova-Malinovska ◽  
M. Tzolov ◽  
M. Kamenova ◽  
N. Tzenov ◽  
M. Sendova-Vassileva ◽  
...  
Keyword(s):  
Light Emission ◽  
Photovoltaic Effect ◽  
Luminescent Properties ◽  
Porous Si ◽  
Photoelectric Properties ◽  
Type C ◽  
P Type ◽  
Silicon Based ◽  
Electrical Bias ◽  
Stain Etching

AbstractThe results of photoelectric properties and electroluminescent studies of structures ZnO/porous Si/p-type c-Si/Al and ZnO/porous Si/p-n c-Si junction/Al are presented. Porous Si is prepared by stain etching of c-Si covered with thin Al film. The transparent ZnO film allows light emission through the top surface of the device under forward electrical bias. Photocurrent is observed under reverse bias and a photovoltaic effect is measured on the p-n junction PS device. The model based on injection of minority carriers through a narrow energy barrier into the porous Si and the presence of the barrier at the interface porous Si/c-Si is suggested for describing the electrical, photoelectric and luminescent properties of the structures.

scholarly journals Dynamically tuned non-classical light emission from atomic defects in hexagonal boron nitride

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Snežana Lazić ◽  
André Espinha ◽  
Sergio Pinilla Yanguas ◽  
Carlos Gibaja ◽  
Félix Zamora ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Information Technologies ◽  
Light Emission ◽  
Hexagonal Boron Nitride ◽  
Theoretical Calculations ◽  
Optical Emission ◽  
Spectral Tuning ◽  
Spectral Detection ◽  
On Chip

Abstract Luminescent defects in hexagonal boron nitride (h-BN) have recently emerged as a promising platform for non-classical light emission. On-chip solutions, however, require techniques for controllable in-situ manipulation of quantum light. Here, we demonstrate the dynamic spectral and temporal tuning of the optical emission from h-BN via moving acousto-mechanical modulation induced by stimulated phonons. When perturbed by the propagating acoustic phonon, the optically probed radiative h-BN defects are periodically strained and their sharp emission lines are modulated by the deformation potential coupling. This results in an acoustically driven spectral tuning within a 2.5-meV bandwidth. Our findings, supported by first-principles theoretical calculations, reveal exceptionally high elasto-optic coupling in h-BN of ~50 meV/%. Temporal control of the emitted photons is achieved by combining the acoustically mediated fine-spectral tuning with spectral detection filtering. This study opens the door to the use of sound for scalable integration of h-BN emitters in nanophotonic and quantum information technologies.

scholarly journals Ce3+:CaSc2O4 Crystal Fibers for Green Light Emission: Growth Issues and Characterization

2014 ◽  
Vol 1655 ◽  
Author(s):  
Detlef Klimm ◽  
Jan Philippen ◽  
Toni Markurt ◽  
Albert Kwasniewski
Keyword(s):  
Melting Point ◽  
Light Emission ◽  
Green Light ◽  
Optical Emission ◽  
Charge Compensation ◽  
Scanning Calorimetry ◽  
Co Doping ◽  
Emission Growth ◽  
Crystal Fibers ◽  
Alkaline Oxides

ABSTRACTCe3+ is known to show broad optical emission peaking in the green spectral range. For the stabilization of 3-valent cerium in ceramic phosphors such as calcium scandate CaSc2O4, often co-doping with sodium for charge compensation is performed (Na+, Ce3+ ↔ 2 Ca2+). At the melting point of CaSc2O4 (≈2110°C), however, alkaline oxides evaporate completely and co-doping is thus no option for crystal growth from the melt. It is shown that even without co-doping Ce3+:CaSc2O4 crystal fibers can be grown from the melt by laser-heated pedestal growth (LHPG) in a suitable reactive atmosphere. Reactive means here that the oxygen partial pressure is a function of temperature and pO2(T) rises for this atmosphere in such a way that Ce3+ is kept stable for all T. Crystal fibers with ≈1 mm diameter and ≤50 mm length were grown and characterized. Differential thermal analysis (DTA) was performed in the pseudo-binary system CaO–Sc2O3, and the specific heat capacity cp(T) of CaSc2O4 was measured up to 1240 K by differential scanning calorimetry (DSC). Near and beyond the melting point of calcium scandate significant evaporation of calcium tends to shift the melt composition towards the Sc2O3 side. Measurements and thermodynamic calculations reveal quantitative data on the fugacities of evaporating species.

Thermal Transformation of Hydrogen Bonds in a-SiC:H Films: Structural and Optical Properties

2005 ◽  
Vol 864 ◽  
Author(s):  
Andrey V. Vasin ◽  
Sergey P. Kolesnik ◽  
Andrey A. Konchits ◽  
Vladimir S. Lysenko ◽  
Alexey N. Nazarov ◽  
...  
Keyword(s):  
Light Emission ◽  
Vacuum Annealing ◽  
Thermal Transformation ◽  
Vacuum Treatment ◽  
Nonradiative Recombination ◽  
Defect States ◽  
Paramagnetic Defect ◽  
Paramagnetic Resonance ◽  
First Time ◽  
Hydrogenated Amorphous

AbstractHydrogenated amorphous silicon carbide (a-SiC:H) films have been deposited using magnetron sputtering technique. Investigation of the effect of the vacuum annealing temperature on photoluminescence properties and paramagnetic defects, and its correlation with structural transformation of a-SiC:H have been performed. Significantly enhanced light emission efficiency after low-temperature vacuum treatment (450 °C) is found due to enhanced passivation of paramagnetic defects associated with carbon-rich chemically disordered structure. Subsequent high-temperature vacuum annealing results in a decrease of luminescent intensity that is associated with increase of carbon related paramagnetic defect states, shown to be the primary nonradiative recombination centres. For the first time silicon-related dangling bonds in a-SiC:H have been detected reliably by electron paramagnetic resonance measurements in annealed samples.

scholarly journals Exploring the Internal Radiative Efficiency of Selective Area Nanowires

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
A. Cavalli ◽  
J. E. M. Haverkort ◽  
E. P. A. M. Bakkers
Keyword(s):  
Solar Cell ◽  
High Growth ◽  
Optical Emission ◽  
Building Blocks ◽  
Growth Conditions ◽  
Material System ◽  
Solar Cell Application ◽  
Precise Control ◽  
Radiative Efficiency ◽  
Selective Area

Nanowires are ideal building blocks for next-generation solar cell applications. Nanowires grown with the selective area (SA) approach, in particular, have demonstrated very high material quality, thanks to high growth temperature, defect-free crystalline structure, and absence of external catalysts, especially in the InP material system. A comprehensive study on the influence of growth conditions and device processing on optical emission is still necessary though. This article presents an investigation of the nanowire optical properties, performed in order to optimize the internal radiative efficiency. In an initial preamble, the motivation for this study is discussed, as well as the morphology and crystallinity of the nanowires. The effect on the nanowire photoluminescence of several intrinsic and extrinsic parameters and factors are then presented in three sections: first, the influence of basic growth conditions such as the temperature and the precursor ratio is studied. Subsequently, the effects of varying dopant molar flows are explored, keeping in mind the intended solar cell application. Third, the manner in which the processing and the passivation affect the nanowire optical emission is discussed. Precise control of the growth conditions allows maximizing the nanowire internal radiative efficiency and thus their performance in solar cells and other optoelectronic devices.

Photoluminescence (PL) and Optically Detected Magnetic Resonance (ODMR) Study of Visible Light Emission from Porous Si

1991 ◽  
Vol 256 ◽  
Author(s):  
P. A. Lane ◽  
L. S. Swanson ◽  
J. Shinar ◽  
S. Chumbley
Keyword(s):  
Light Emission ◽  
Porous Si ◽  
Temperature Dependent ◽  
X Band ◽  
Amorphous Si ◽  
Optically Detected ◽  
Increasing Temperature ◽  
Hydrogenated Amorphous ◽  
Visible Light Emission ◽  
Si Wafer

ABSTRACTThe photoluminescence (PL) and X-band ODMR of porous Si layers is described and discussed. The layers were prepared by anodizing the (100) face of a Si wafer at 20 mA/cm2 in 20% HF for 5 mai and passively soaking them in 36% HF for up to 10 hrs. The PL was broad and featureless, extending from ˜1.5 to ˜2.1 eV and peaking at 1.68 eV. Its intensity slightly increased upon cooling to 90 K, and then strongly decreased at lower temperatures. A ˜20 G wide asymmetric PL-enhancing ODMR was observed at g ˜2.0031 ±I 0.0009, which could be fit to a sum of two Gaussians. Their g-values were slightly temperature dependent. The ODMR intensity strongly decreased with increasing temperature, and was unobservable above ˜80 K. The results are compared to the optical properties of hydrogenated amorphous Si.

Experimental Study on the Effect of Different Noble Gas Admixtures on the Gas Temperature of Oxygen Plasma

2005 ◽  
Vol 8 (1) ◽  
Author(s):  
K. Naoi ◽  
T. Sakamoto ◽  
H. Matsuura ◽  
H. Akatsuka
Keyword(s):  
Oxygen Plasma ◽  
Rotational Temperature ◽  
Noble Gas ◽  
Optical Emission ◽  
Radiative Transition ◽  
Band Spectrum ◽  
Gas Temperature ◽  
Inner Diameter ◽  
Discharge Pressure ◽  
Gas Admixtures

AbstractWe measured rotational temperature of oxygen plasma by optical emission spectroscopy (OES) in order to examine approximate value of its gas temperature. We generated microwave discharge oxygen plasma in a cylindrical quartz tube whose inner diameter 26 mm with its discharge pressure 0.5 - 2.0 Torr. We measured the band spectrum of radiative transition A

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