Nonequilibrium Carrier Dynamics Studied in Er, O-Codoped GaAs by Pump-Probe Reflection Technique

2005 ◽  
Vol 866 ◽  
Author(s):  
Yasufumi Fujiwara ◽  
Kazuhiko Nakamura ◽  
Shoichi Takemoto ◽  
Yoshikazu Terai ◽  
Masato Suzuki ◽  
...  
Keyword(s):  
Gradual Increase ◽  
Carrier Dynamics ◽  
Single Atom ◽  
Time Resolved ◽  
Pump Probe ◽  
Pump And Probe ◽  
Steep Decrease ◽  
Luminescence Time ◽  
Atom Configuration ◽  
Nonequilibrium Carriers

AbstractCarrier dynamics in Er,O-codoped GaAs (GaAs:Er,O) have been systematically investigated by means of a pump and probe reflection technique with a mode-locked Ti:sapphire laser. In GaAs:Er,O, it has been found that the codoping produces a single atom configuration (Er-20 configuration) as an Er atom located at the Ga sublattice with two adjacent O atoms together with two As atoms, resulting in extremely strong Er luminescence. Time-resolved reflectivity of GaAs:Er,O exhibited an abrupt increase in amplitude, followed by a steep decrease to negative in less than 1 ps and then a gradual increase in approximately 100 ps. The steep decrease is due to bandgap renormalization. The gradual increase in reflectivity depended strongly on Er concentration, indicating that a trap induced by Er and O codoping plays an important role in dynamics of nonequilibrium carriers in GaAs:Er,O.

scholarly journals Extraction of Fast Changes in the Structure of a Disordered Ensemble of Photoexcited Biomolecules

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
H.-C. Poon ◽  
M. Schmidt ◽  
D. K. Saldin
Keyword(s):  
Structural Changes ◽  
Ultrashort Pulses ◽  
Fast Time ◽  
X Rays ◽  
Multiple Diffraction ◽  
Time Resolved ◽  
Pump Probe ◽  
Pump And Probe ◽  
Time Variations ◽  
Diffraction Patterns

Using pump-probe experiments of varying time intervals between pump and probe, the method of time-resolved crystallography has given many insights into the fast time variations of crystallized molecules as a result of photoexcitation. We show here that quantities extractable from multiple diffraction patterns of dissolved molecules in random orientations, as measured using powerful ultrashort pulses of X-rays, also contain information about structural changes of a molecule on photoexcitation.

Femtosecond Carrier Dynamics in Nanocrystalline Silicon Films: The Effect of the Degree of Crystallinity

2001 ◽  
Vol 664 ◽  
Author(s):  
K.E. Myers ◽  
Q. Wang ◽  
S.L. Dexheimer
Keyword(s):  
Near Infrared ◽  
Heterogeneous Material ◽  
Nanocrystalline Silicon ◽  
Carrier Dynamics ◽  
Degree Of Crystallinity ◽  
Time Resolved ◽  
Carrier Relaxation ◽  
Pump Probe ◽  
Silicon Thin Films ◽  
The Degree Of Crystallinity

ABSTRACTWe present studies of the ultrafast dynamics of photoexcited carriers in HWCVD nanocrystalline silicon thin films to address the underlying physics of carrier relaxation and recombination processes in this heterogeneous material. The degree of crystallinity is controlled by varying the H-dilution during deposition, yielding materials with increasingly larger grain size and crystalline fraction at higher dilution values. Time-resolved measurements of the carrier dynamics were made using a femtosecond pump-probe method, in which a short pump pulse excites carriers in the sample and a time-delayed probe pulse measures the resulting change in the optical properties as a function of the pump-probe delay time. Photoexcitation of carriers with pulses 35 fs in duration centered at 1.55 eV results in a net induced absorbance signal in the near-infrared that is analyzed in terms of a multi-component response that includes contributions from the silicon crystallites and the amorphous matrix.

Behaviors of Nonequilibrium Carriers in Er, O-Codoped GaAs for 1.5μm Light-Emitting Devices with Extremely Stable Wavelength

2006 ◽  
Vol 512 ◽  
pp. 159-164
Author(s):  
Yasufumi Fujiwara ◽  
Atsushi Koizumi ◽  
Kazuhiko Nakamura ◽  
Masato Suzuki ◽  
Yoshikazu Takeda ◽  
...  
Keyword(s):  
Active Layer ◽  
Diffusion Length ◽  
Forward Bias ◽  
Active Layer Thickness ◽  
Time Resolved ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Short Lifetime ◽  
Steep Decrease ◽  
Nonequilibrium Carriers

We have fabricated GaInP/Er,O-codoped GaAs (GaAs:Er,O)/GaInP double heterostructure (DH) light-emitting diodes (LEDs) and successfully observed 1.5 µm electroluminescence (EL) due to an Er-2O center under forward bias at room temperature. Er excitation cross section by current injection decreased with increasing GaAs:Er,O active layer thickness, implying reduced diffusion length of injected carriers in the active layer. Carrier dynamics in GaAs:Er,O have also been investigated by means of a pump and probe reflection technique. Time-resolved reflectivity of GaAs:Er,O exhibited a characteristic dip after a steep decrease to negative in less than 10 ps. The analysis of the characteristic dip revealed short lifetime in range of ps for photoexcited carriers. The extremely short lifetime is quite coincident with the reduced diffusion length of injected carriers, and suggests that a trap induced by Er and O codoping would play an important role in dynamics of nonequilibrium carriers in GaAs:Er,O.

scholarly journals Bases for time-resolved probing of transient carrier dynamics by optical pump–probe scanning tunneling microscopy

Nanoscale ◽  
2013 ◽  
Vol 5 (19) ◽  
pp. 9170 ◽  
Author(s):  
Munenori Yokota ◽  
Shoji Yoshida ◽  
Yutaka Mera ◽  
Osamu Takeuchi ◽  
Haruhiro Oigawa ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Carrier Dynamics ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe

Photoconversion of Spiropyran to Merocyanine in a Monolayer Observed Using Nanosecond Pump-Probe Brewster Angle Reflectometry

2012 ◽  
Vol 65 (3) ◽  
pp. 283 ◽  
Author(s):  
Bernhard Siebenhofer ◽  
Sergey Gorelik ◽  
Anton V. Sadovoy ◽  
Martin J. Lear ◽  
Hong Yan Song ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Brewster Angle ◽  
Time Resolved ◽  
Pump Probe ◽  
Second Stage ◽  
Pump And Probe ◽  
New Apparatus ◽  
Two Stages ◽  
Kinetics Of ◽  
Uv Excitation

A new apparatus for nanosecond-time-resolved Brewster angle reflectometry is described that can be used to measure transient angle-resolved reflectivity changes in thin films and monolayers in a single pulsed laser shot. In order to achieve this, a cylindrical lens is placed in the probe beam path replacing the goniometer that is usually used for angular scanning in other systems. Using two synchronized nanosecond pulsed lasers in pump-probe configuration it is possible to measure the kinetics of photoinduced conformational changes by altering the delay between pump and probe pulses. The system was used to observe nanosecond time-resolved photodynamics in a spiropyran monolayer at the air-water interface. After UV excitation the spiropyran converted to its merocyanine form in two stages. The first stage occurred with a timescale close to the instrument time resolution (tens of nanoseconds) whereas the second stage occurred over a few hundred nanoseconds.

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