scholarly journals Large Persistent Photochromic Effect Due to DX Centers in AlSb Doped with Selenium

1995 ◽  
Vol 378 ◽  
Author(s):  
P. Becla ◽  
A. G. Witt ◽  
J. Lagowski ◽  
W. Walukiewicz
Keyword(s):  
Absorption Coefficient ◽  
Conduction Band ◽  
Spectral Range ◽  
Donor Level ◽  
Dx Centers ◽  
Enhanced Absorption ◽  
Photochromic Effect ◽  
Dx Center

AbstractA large photochromic effect has been observed in bulk AlSb crystals doped with Se. Illumination with the light of energy higher than 1 eV leads to an increase of the absorption coefficient in the spectral range 0.1 eV to 1.6 eV. The enhanced absorption is persistent at the temperatures below about 100 K. The effect is a manifestation of a DX-like bistability of Se donors. The illumination transfers the electrons from the DX center to a metastable hydrogenic level. The increased absorption with peaks around 0.2 eV and 0.5 eV is due to photoionization from the donor level to X1 and X3 minima of the conduction band

scholarly journals A Photocapture Test of DX-Center Models

1989 ◽  
Vol 163 ◽  
Author(s):  
Harold P. Hjalmarson ◽  
S. R. Kurtz ◽  
T. M. Brennan
Keyword(s):  
Conduction Band ◽  
Cross Section ◽  
Threshold Energy ◽  
Photoionization Cross Section ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Null Result ◽  
Dx Center

AbstractThe DX-center model is widely used to explain data for the persistent photoconductivity (PPC) effect. An analysis of the DX-center model suggests a new experiment to test its correctness. In this experiment, photons near the threshold energy of the photoionization cross-section for the DX-center induce transitions from the partially occupied conduction band to empty DX-centers. This mechanism, which we call photocapture, competes with the usual photoionization which empties the DX-centers. The photocapture cross-section is estimated and an experimental attempt is made to detect photocapture. The significance of the null result is discussed.

DX Center Energy Level in InxAl1−xAs Compounds

1999 ◽  
Vol 573 ◽  
Author(s):  
Hüseyin Sari ◽  
Harry H. wieder
Keyword(s):  
Energy Level ◽  
Conduction Band ◽  
Canonical Ensemble ◽  
Grand Canonical Ensemble ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Indium Concentration ◽  
Self Consistent ◽  
Dx Center ◽  
Grand Canonical

ABSTRACTThe presence of DX centers in InxAl1−xAs, primarily in the indirect portion of the InxAl1−xAs bandgap, has been determined using modulation doped InxAl1−xAs/InyGa1−yAs heterostructures by means of persistent photoconductivity (PPC) and galvanomagnetic measurements. From the cooling bias experiment, the PPC, and self consistent Poisson and Schrddinger simulations the ratio of the ionized shallow donors to the DX centers is obtained. Using this ratio in the grand canonical ensemble (GCE) the energy level of DX centers is determined. It is found that the DX energy level merges with the conduction band at x ≅ 0.42 and is resonant with the conduction band in higher indium concentration.

DX Centers in GaAs and AlxGal-x.As: Properties and Influence on Material and Device Characteristics

1987 ◽  
Vol 104 ◽  
Author(s):  
P. M. Mooney
Keyword(s):  
Low Temperature ◽  
Carrier Concentration ◽  
Conduction Band ◽  
Energy State ◽  
Free Carrier ◽  
Free Carrier Concentration ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Compensation Mechanisms ◽  
Dx Center

ABSTRACTThe DX center, the lowest energy state of the donor in AlGaAs with x > 0.22, is responsible for the reduced conductivity as well as the persistent photoconductivity observed in this material at low temperature. Extensive studies of the properties of this level and of its effects on the characteristics of some heterojunction devices are reviewed here. Recent measurements are presented showing that the characteristics of the DX center remain essentially unchanged when it is resonant with the conduction band (x < 0.22) and that, independent of other compensation mechanisms, the DX center therefore limits the free carrier concentration in GaAs to a maximum of about 2×1019 cm− 3.

Evidence for Metastabile State of DX Center in AxGa1-xAs

1992 ◽  
Vol 262 ◽  
Author(s):  
Subhasis Ghosh ◽  
Vikram Kumar
Keyword(s):  
Activation Energy ◽  
Deep Level Transient Spectroscopy ◽  
Thermal Activation ◽  
Deep Level ◽  
Thermal Activation Energy ◽  
Dx Centers ◽  
Dx Center ◽  
Transient Spectroscopy ◽  
Silicon Doped ◽  
First Time

ABSTRACTPhoto-Deep Level Transient Spectroscopy with 1.38 eV light reveals a new level with thermal activation energy 0.2 eV of DX centers in silicon doped Alx Ga1-xAs (x = 0.26) for the first time. The observation of this level directly proves the negative-U properties of DX centers and the existence of thermodynamically metastable state DX.

Optical Spectroscopy as a Tool for Observation of Porous SiC Graphitization

2005 ◽  
Vol 483-485 ◽  
pp. 261-264
Author(s):  
V.B. Shuman ◽  
N.S. Savkina
Keyword(s):  
Thermal Treatment ◽  
Absorption Coefficient ◽  
Porous Layer ◽  
Spectral Range ◽  
Optical Transmission ◽  
Near Infrared ◽  
Wet Oxidation ◽  
Infrared Spectral Range ◽  
Infrared Spectral ◽  
Porous Sic

We have studied effects of thermal treatment in vacuum and wet oxidation on the optical transmission of SiC samples with porous layer on the Si face in the visible and near infrared spectral range. An analysis of changes in the absorption coefficient shows that the process of graphitization in vacuum begins at a temperature below 700°C and can be observed at wet oxidation at 1000°C.

scholarly journals CHARGE WAVES IN DOUBLE DOPED PHOTOCHROMIC LITHIUM NIOBATE CRYSTALS

2012 ◽  
Vol 15 ◽  
pp. 54-60 ◽  
Author(s):  
RUBEN HOVSEPYAN ◽  
ARMEN POGHOSYAN ◽  
EDUARD VARDANYAN
Keyword(s):  
Lithium Niobate ◽  
Absorption Coefficient ◽  
Analytical Model ◽  
Experimental Studies ◽  
Light Illumination ◽  
Double Doping ◽  
Time Space ◽  
Photochromic Effect ◽  
Lithium Niobate Crystals

We are presenting the experimental studies of time-space characteristics of photochromic effect in lithium niobate crystals with double doping. The photoinduced autowaves of absorption coefficient changes under the light illumination of limited part of crystal were found. An analytical model is proposed for the explanation of appearance and spreading of charge waves.

scholarly journals Showcasing the optical properties of monocrystalline zinc phosphide thin films as an earth-abundant photovoltaic absorber

2022 ◽  
Author(s):  
Elias Zsolt Stutz ◽  
Mahdi Zamani ◽  
Djamshid Damry ◽  
Lea Buswell ◽  
Rajrupa Paul ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Absorption Coefficient ◽  
Spectral Range ◽  
Zinc Phosphide ◽  
Single Junction ◽  
Photovoltaic Applications ◽  
Earth Abundant ◽  
High Absorption Coefficient ◽  
High Absorption

Zinc phosphide, Zn3P2, is a semiconductor with a high absorption coefficient in the spectral range relevant for single junction photovoltaic applications. It is made of elements abundant in the Earth’s...

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