Picosecond Raman light-scattering study of hot carriers in InP

1987 ◽  
Vol 65 (8) ◽  
pp. 831-837 ◽  
Author(s):  
Kam Wan ◽  
Jeff F. Young ◽  
A. J. SpringThorpe
Keyword(s):  
Diffusion Constant ◽  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Uniform Density ◽  
Time Resolved ◽  
Coupled Mode ◽  
Longitudinal Optic ◽  
Longitudinal Optic Phonon ◽  
Recombination Velocity ◽  
Nonequilibrium Carriers

We demonstrate a novel method of using picosecond time-resolved Raman scattering to study the kinetics of nonequilibrium carriers in semiconductors. A pump–probe technique employing two separate lasers of different intensities, focal-spot sizes, and pulse durations is used to ensure that a plasma of uniform density is probed. The nonequilibrium-carrier density near the surface of a semi-insulating InP sample is estimated by fitting the photoexcited plasmon – longitudinal optic phonon coupled-mode peak in the Raman spectra. The dielectric function used in the calculation includes contributions from intraband transitions of electrons, light holes, and heavy holes as well as from interband transitions of the holes. The temporal evolution of the optically excited carrier population is modelled using a one-dimensional diffusion equation. The ambipolar diffusion constant and the surface-recombination velocity of the nonequilibrium carriers are found to be comparable to estimated values based on extrapolation of equilibrium properties.

scholarly journals Carrier Lifetime Enhancement in a Tellurium Nanowire/PEDOT:PSS Nanocomposite by Sulfur Passivation

2015 ◽  
Vol 1742 ◽  
Author(s):  
James N. Heyman ◽  
Ayaskanta Sahu ◽  
Nelson E. Coates ◽  
Brittany Ehmann ◽  
Jeffery J. Urban
Keyword(s):  
Carrier Lifetime ◽  
Surface Recombination ◽  
Structural Defects ◽  
Surface Recombination Velocity ◽  
Matrix Composites ◽  
Time Resolved ◽  
Dc Conductivities ◽  
Sulfur Passivation ◽  
Recombination Velocity ◽  
Tellurium Nanowires

ABSTRACTWe report static and time-resolved terahertz (THz) conductivity measurements of a highperformance thermoelectric material containing tellurium nanowires in a PEDOT:PSS matrix. Composites were made with and without sulfur passivation of the nanowires surfaces. The material with sulfur linkers (TeNW/PD-S) is less conductive but has a longer carrier lifetime than the formulation without (TeNW/PD). We find real conductivities at f = 1THz of σTeNW/PD = 160 S/cm and σTeNW/PD-S = 5.1 S/cm. These values are much larger than the corresponding DC conductivities, suggesting DC conductivity is limited by structural defects. The free-carrier lifetime in the nanowires is controlled by recombination and trapping at the nanowire surfaces. We find surface recombination velocities in bare tellurium nanowires (22m/s) and TeNW/PD-S (40m/s) that are comparable to evaporated tellurium thin films. The surface recombination velocity in TeNW/PD (509m/s) is much larger, indicating a higher interface trap density.

A simple formulation of the saturation current density in heavily doped emitters

2003 ◽  
Vol 81 (9) ◽  
pp. 1109-1120 ◽  
Author(s):  
A Zouari ◽  
A Ben Arab
Keyword(s):  
Current Density ◽  
Diffusion Constant ◽  
Surface Recombination ◽  
Simple Expression ◽  
The Other ◽  
Surface Recombination Velocity ◽  
Hole Density ◽  
Simple Formulation ◽  
Heavily Doped ◽  
Recombination Velocity

In a non-uniformly and heavily doped emitter region of a bipolar transistor, the continuity equation and the minority-current equation cannot be solved exactly in closed form. This paper shows that the calculation of minority-carrier current density can be calculated by a simple approach. This approach is based on the average value of the equilibrium hole density p0, diffusion constant Dp, and lifetime τp of minority carriers and leads to two coupled differential equations of the first order. These equations can be solved easily and can give a simple expression for the current density. Three definitions of the average values of p0, Dp, and τp are used and lead to three expressions for the emitter current density. The latter is identical to the one established by Rinaldi using another mathematical analysis and gives very accurate results for a shallow emitter (W < 1 µm), irrespective of the range peak doping level N(W) and surface-recombination velocity S. On the other hand, the other two expressions lead also to accurate results for the current density depending on the value of the surface-recombination velocity, but cannot be used when N(W) is greater than 1020 cm–3 and W is superior to 0.1 µm. PACS Nos.: 72.10.–d, 72.20.–i

Deep Traps and Charge Carrier Lifetimes in 4H-SiC Epilayers

2006 ◽  
Vol 527-529 ◽  
pp. 493-496 ◽  
Author(s):  
Sung Wook Huh ◽  
Joseph J. Sumakeris ◽  
A.Y. Polyakov ◽  
Marek Skowronski ◽  
Paul B. Klein ◽  
...  
Keyword(s):  
Deep Level ◽  
Surface Recombination ◽  
Deep Trap ◽  
Analytical Form ◽  
Optical Injection ◽  
Surface Recombination Velocity ◽  
Time Resolved ◽  
Electron Traps ◽  
Carrier Lifetimes ◽  
Recombination Velocity

Carrier lifetimes and the dominant electron and hole traps were investigated in a set of thick (9-104mm) undoped 4H-SiC epitaxial layers grown by CVD homoepitaxy. Deep trap spectra were measured by deep level transient spectroscopy (DLTS) with electrical or optical injection, while lifetimes were measured by room temperature time-resolved photoluminescence (PL). The main electron traps detected in all samples were due to Ti, Z1/Z2 centers, and EH6/EH7 centers. Two boron-related hole traps were observed with activation energies of 0.3 eV (boron acceptors) and 0.6 eV (boron-related D centers). The concentration of electron traps decreased with increasing layer thickness and increased toward the edge of the wafers. PL lifetimes were in the 400 ns-1800 ns range with varying injection and generally correlated with changes in the density of Z1/Z2 and to a lesser extent the EH6/EH7 electron traps. However, the results of DLTS measurements on p-i-n diode structures suggest that the capture of injected holes is much more efficient for the Z1/Z2 traps compared to the EH6/EH7 centers making the Z1/Z2 more probable candidates for the role of lifetime killers. A good fit of the thickness dependence of the measured lifetimes to the usual analytical form was obtained assuming that Z1/Z2 is the dominant hole recombination center and that the surface recombination velocity was 2500 cm/sec.

scholarly journals Numerical Simulation Analysis of Ag Crystallite Effects on Interface of Front Metal and Silicon in the PERC Solar Cell

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 592
Author(s):  
Myeong Sang Jeong ◽  
Yonghwan Lee ◽  
Ka-Hyun Kim ◽  
Sungjin Choi ◽  
Min Gu Kang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
High Efficiency ◽  
Open Circuit Voltage ◽  
Surface Recombination ◽  
Open Circuit ◽  
Surface Recombination Velocity ◽  
Metal Interface ◽  
Ag Crystallites ◽  
Recombination Velocity

In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails an increase in the surface recombination velocity and a drop in the open-circuit voltage of the solar cell; hence, controlling the recombination velocity at the metal-silicon interface becomes a critical factor in the process. In this study, the distribution of Ag crystallites formed on the silicon-metal interface, the surface recombination velocity in the silicon-metal interface and the resulting changes in the performance of the Passivated Emitter and Rear Contact (PERC) solar cells were analyzed by controlling the firing temperature. The Ag crystallite distribution gradually increased corresponding to a firing temperature increase from 850 ∘C to 950 ∘C. The surface recombination velocity at the silicon-metal interface increased from 353 to 599 cm/s and the open-circuit voltage of the PERC solar cell decreased from 659.7 to 647 mV. Technology Computer-Aided Design (TCAD) simulation was used for detailed analysis on the effect of the surface recombination velocity at the silicon-metal interface on the PERC solar cell performance. Simulations showed that the increase in the distribution of Ag crystallites and surface recombination velocity at the silicon-metal interface played an important role in the decrease of open-circuit voltage of the PERC solar cell at temperatures of 850–900 ∘C, whereas the damage caused by the emitter over fire was determined as the main cause of the voltage drop at 950 ∘C. These results are expected to serve as a steppingstone for further research on improvement in the silicon-metal interface properties of silicon-based solar cells and investigation on high-efficiency solar cells.

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