Layer Disordering and Carrier Concentration in Heavily Carbon-Doped AlGaAs/GaAs Superlattices

1993 ◽  
Vol 300 ◽  
Author(s):  
H. M. You ◽  
T. Y. Tan ◽  
U. M. Gösele ◽  
G. E. Höfler ◽  
K. C. Hsieh ◽  
...  
Keyword(s):  
Fermi Level ◽  
Carrier Concentration ◽  
Hole Concentration ◽  
Concentration Profiles ◽  
Precipitation Mechanism ◽  
Carbon Doped ◽  
Effect Model ◽  
The One ◽  
Level Effect

ABSTRACTAl-Ga interdiffusion, carbon acceptor diffusion, and hole reduction were studied in carbondoped Al0.4Ga0.6As/GaAs superlattices (SL). Al-Ga interdiffusion was found to be most prominent for Ga-rich annealing, with the hole concentrations in the SL almost intact during annealing. For As-rich annealing, the interdiffusivity values, DAI.Ga, are in approximate agreement with those predicted by the Fermi-level effect model, and the hole concentrations in the SL decreased dramatically after annealing. By analyzing the measured hole concentration profiles, it was found that both carbon acceptor diffusion and reduction have occurred during annealing, with both depending on As4 pressure values to the one quarter power. These As4 pressure dependencies indicate that carbon diffuses via the interstitial-substitutional mechanism while hole reduction is governed by a precipitation mechanism.

Fermi-Level Effect on Group III Atom Interdiffusion in III-V Compounds: Bandgap Heterogeneity and Low Silicon-Doping

1997 ◽  
Vol 490 ◽  
Author(s):  
C.-H. Chen ◽  
U. Gösele ◽  
T. Y. Tan
Keyword(s):  
Fermi Level ◽  
Equilibrium Concentration ◽  
Electric Field Effect ◽  
Silicon Doping ◽  
Group Iii ◽  
Semiconductor Superlattice ◽  
Effect Model ◽  
N Doping ◽  
Short Annealing ◽  
Level Effect

ABSTRACTHeavy n-doping enhanced disordering of GaAs based III-V semiconductor superlattice or quantum well layers, as well as the diffusion of Si in GaAs have been previously explained by the Fermi-level effect model with the triply-negatively-charged group III lattice vacancies identified to be the responsible point defect species. These vacancies have a thermal equilibrium concentration proportional to the cubic power of the electron concentration n, leading to the same dependence of the layer disordering rate. In this paper, in addition, we take into account also the electric field effect produced by the material bandgap heterogeneity and/or hetero-junctions. In heavily n-doped or long time annealing cases, this effect is negligible. At low n-doping levels and for short annealing times, the layer disordering rate can be enhanced or reduced by this effect. Available experimental results of low Si-doped and very short-time annealed samples have been satisfactorily fitted using the Fermi-level effect model.

Very high hole concentrations in C-doped InGaAs using new sources with APOMVPE

1997 ◽  
Vol 485 ◽  
Author(s):  
A. Tandon ◽  
R. M. Cohen
Keyword(s):  
High Temperature ◽  
Structural Change ◽  
Carrier Concentration ◽  
Hole Concentration ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Carbon Doped ◽  
High Temperature Anneal ◽  
Order Of Magnitude ◽  
P Type

AbstractNew sources have been used to grow the first carbon doped, highly p-type InxGa1-xAs (0.2>x>0.7) epilayers on InP substrates by atmospheric pressure organometallic vapor phase epitaxy (APOMVPE). Excellent morphology was obtained simultaneously with high hole concentrations at growth temperatures near 450 °C. High hole concentrations of 1.6×1019 – 8.7×1019 cm−3 (the highest reported to date for APOMVPE), and the corresponding room temperature hole mobilities of 65 – 25 cm2/s, respectively, have been obtained from Hall measurements. X-ray diffraction is consistent with excellent crystal quality. Annealing at temperatures of T=400–500 °C in the presence of either nitrogen or hydrogen was found to change the carrier concentration by only 0–15%. However, after annealing at T=650 °C, irreversible changes occurred in the InGaAs. After a high temperature anneal, reversible order of magnitude changes in the hole concentration was obtained upon further annealing at low temperatures, depending upon the ambient. These results conclusively show that hydrogen does not passivate C acceptor ions in InGaAs. Since changes in the carrier concentration become substantial and reversible only after high temperature annealing, the results strongly suggest that a structural change occurred in the crystal at high temperatures. We consider it likely that this structural change is the precipitation of carbon out of a supersaturated solid solution, and that hydrogen atoms associated with these precipitates act as donors which compensate the hole concentration.

Fermi-Level Effect and Junction Carrier Concentration Effect on Boron Distribution in GexSil−x/Si Heterostructures

1998 ◽  
Vol 535 ◽  
Author(s):  
CHang-Ho Chen ◽  
Ulrich M. Gösele ◽  
Teh Y. Tan
Keyword(s):  
Diffusion Process ◽  
Fermi Level ◽  
Carrier Concentration ◽  
Chemical Effect ◽  
Boron Diffusion ◽  
Dopant Segregation ◽  
Boron Distribution ◽  
The Difference ◽  
Level Effect ◽  
Positively Charged

AbstractDopant segregation mechanism in general involves the chemical effect, the Fermi-level effect, and the effect of the junction carrier concentrations. Satisfactory fits of available B distribution profiles in GexSil−x/Si heterostructures have been obtained using such a model, but with the chemical effect not important. The Fermi-level effect determines the difference in the ionized B solubilities in GexSil−x and Si. The singly-positively charged crystal self-interstitials I+ governs the boron diffusion process. The junction carrier concentration affects the concentration of I+ and solubility of B in the region and hence controls B diffusion across the heterojunction.

Simulation of Under- and Supersaturation of Gallium Vacancies in Gallium Arsenide During Silicon in- and Outdiffusion

1997 ◽  
Vol 490 ◽  
Author(s):  
C.-H. Chen ◽  
U. Gösele ◽  
T. Y. Tan
Keyword(s):  
Gallium Arsenide ◽  
Fermi Level ◽  
Point Defect ◽  
Surface States ◽  
Effect Model ◽  
N Doping ◽  
Defect Species ◽  
Concentration Of Electrons ◽  
Level Effect ◽  
Doping Condition

ABSTRACTThe diffusivity of Si in GaAs shows a dependence on the cubic power of its concentration or the concentration of electrons n under both in- and outdiffusion conditions. Hence, the diffusion of Si in GaAs is consistent with the Fermi-level effect model invoking the triply-negatively-charged Ga vacancies, , as the point defect species responsible for diffusion to occur on the Ga sublattice under n-doping condition. However, the Si diffusivity values of the indiffusion cases is several orders of magnitude smaller than those of the outdiffusion cases at the same Si concentrations. This means that the two apparent Si diffusivity values under intrinsic conditions will contain also the same discrepancy, which has been previously assessed to be due to a undersaturation in indiffusion cases and a supersaturation in outdiffusion cases. In this study we have calculated the under- and supersaturation values using the known Si diffusivities. We found that the GaAs surface states play a key role in the development of the under- and supersaturations.

scholarly journals Restructured single parabolic band model for quick analysis in thermoelectricity

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jianbo Zhu ◽  
Xuemei Zhang ◽  
Muchun Guo ◽  
Jingyu Li ◽  
Jinsuo Hu ◽  
...  
Keyword(s):  
Fermi Level ◽  
Carrier Concentration ◽  
Carrier Mobility ◽  
Optimization Design ◽  
State Of The Art ◽  
Band Model ◽  
Carrier Effective Mass ◽  
Intermediate Variables ◽  
Level Calculation ◽  
Spb Model

AbstractThe single parabolic band (SPB) model has been widely used to preliminarily elucidate inherent transport behaviors of thermoelectric (TE) materials, such as their band structure and electronic thermal conductivity, etc. However, in the SPB calculation, it is necessary to determine some intermediate variables, such as Fermi level or the complex Fermi-Dirac integrals. In this work, we establish a direct carrier-concentration-dependent restructured SPB model, which eliminates Fermi-Dirac integrals and Fermi level calculation and emerges stronger visibility and usability in experiments. We have verified the reliability of such restructured model with 490 groups of experimental data from state-of-the-art TE materials and the relative error is less than 2%. Moreover, carrier effective mass, intrinsic carrier mobility and optimal carrier concentration of these materials are systematically investigated. We believe that our work can provide more convenience and accuracy for thermoelectric data analysis as well as instructive understanding on future optimization design.

Synergistic optimization of carrier transport and thermal conductivity in Sn-doped Cu2Te

2018 ◽  
Vol 6 (39) ◽  
pp. 18928-18937 ◽  
Author(s):  
Yuchong Qiu ◽  
Ying Liu ◽  
Jinwen Ye ◽  
Jun Li ◽  
Lixian Lian
Keyword(s):  
Thermal Conductivity ◽  
Fermi Level ◽  
Carrier Concentration ◽  
Power Factor ◽  
Carrier Transport ◽  
Lone Pair ◽  
Thermoelectric Performance ◽  
Degenerate Semiconductors ◽  
Lone Pair Electrons

Doping Sn into the Cu2Te lattice can synergistically enhance the power factor and decrease thermal conductivity, leading to remarkably optimized zTs. The lone pair electrons from the 5s orbital of Sn can increase the DOS near the Fermi level of Cu2Te to promote PF and reduce κe by decreasing the carrier concentration. This study explores a scalable strategy to optimize the thermoelectric performance for intrinsically highly degenerate semiconductors.

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