The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
W. Walukiewicz - One of the best experts on this subject based on the ideXlab platform.
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on the predictive quantitative properties of the amphoteric Native Defect model
Semiconductor Science and Technology, 2019Co-Authors: Stefan P Svensson, W. Walukiewicz, W L Sarney, W A Beck, Leonardo HsuAbstract:The amphoteric Native Defect model phenomenologically explains and categorizes observed background doping concentrations and accounts for the doping limitations in compound semiconductors. Here, we test and verify the model's capabilities as a quantitative, predictive tool. We demonstrate that the nature, (donor or acceptor), of non-stoichiometry related vacancy-like Defects in the (Al,Ga,In)(As,Sb) system is determined by the position of the intrinsic Fermi energy, E Fi at the growth temperature relative to the Fermi level stabilization energy, E FS , a universal energy reference located at 4.9 eV below the vacuum level. We show that a dramatic and predictable conduction type-flip from n- to p-type occurs when E Fi is deliberately shifted from below to above E FS .
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bistable amphoteric Native Defect model of perovskite photovoltaics
Journal of Physical Chemistry Letters, 2018Co-Authors: W. Walukiewicz, I Reystolle, Guifang Han, M Jaquez, Danny Broberg, Wei Xie, Matthew SherburneAbstract:The past few years have witnessed unprecedented rapid improvement of the performance of a new class of photovoltaics based on halide perovskites. This progress has been achieved even though there is no generally accepted mechanism of the operation of these solar cells. Here we present a model based on bistable amphoteric Native Defects that accounts for all key characteristics of these photovoltaics and explains many idiosyncratic properties of halide perovskites. We show that a transformation between donor-like and acceptor-like configurations leads to a resonant interaction between amphoteric Defects and free charge carriers. This interaction, combined with the charge transfer from the perovskite to the electron and hole transporting layers results in the formation of a dynamic n-i-p junction whose photovoltaic parameters are determined by the perovskite absorber. The model provides a unified explanation for the outstanding properties of the perovskite photovoltaics, including hysteresis of J–V characte...
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bistable amphoteric Native Defect model of perovskite photovoltaics
arXiv: Materials Science, 2018Co-Authors: W. Walukiewicz, I Reystolle, Guifang Han, M Jaquez, Danny Broberg, Wei Xie, Matthew SherburneAbstract:The past few years have witnessed unprecedented rapid improvement of the performance of a new class of photovoltaics based on halide perovskites. This progress has been achieved even though there is no generally accepted mechanism of the operation of these solar cells. Here we present a model based on bistable amphoteric Native Defects that accounts for all key characteristics of these photovoltaics and explains many idiosyncratic properties of halide perovskites. We show that a transformation between donor-like and acceptor-like configurations leads to a resonant interaction between amphoteric Defects and free charge carriers. This interaction, combined with the charge transfer from the perovskite to the electron and hole transporting layers results in the formation of a dynamic n-i-p junction whose photovoltaic parameters are determined by the perovskite absorber. The model provides a unified explanation for the outstanding properties of the perovskite photovoltaics, including hysteresis of J-V characteristics and ultraviolet light-induced degradation.
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Defect Reactions at Metal-Semiconductor and Semiconductor-Semiconductor Interfaces
MRS Proceedings, 2011Co-Authors: W. WalukiewiczAbstract:A recently proposed, new approach to the problem of Native Defect formation in compound semiconductors is presented. The approach is based on the concept of amphoteric Native Defects. It is shown that the Defect formation energy as well as structure and properties of simple Native Defects depend on the location of the Fermi level with respect to an internal energy reference: the Fermi level stabilization energy. The known location of the stabilization energy determines the electronic part of the Defect formation energy and allows for a quantitative description of a variety of phenomena including: the formation of Defects at metal-semiconductor interfaces, doping induced superlattice intermixing and limitations of free carrier concentrations in semiconductors.
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Native Defect controlled n type conductivity in inn
Physica B-condensed Matter, 2006Co-Authors: W. Walukiewicz, R E Jones, Leon Hsu, Z Lilientalweber, J W Ager, E E Haller, W J SchaffAbstract:Abstract High-energy particle irradiation has been shown previously to be a method for n-type doping of InN. Here we irradiated InN with H + and He + particles to study the dependence of the electron mobility on electron concentrations varying from mid-10 18 to mid-10 20 cm −3 . We find that the electron mobility is limited by scattering from the ionized Defects created by irradiation, resulting in a strong correlation between mobility and electron concentration. Furthermore, our calculations suggest that the radiation-induced Defects may be triply charged donors.
C. D. Beling - One of the best experts on this subject based on the ideXlab platform.
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Interfacial Fermi level and surface band bending in Ni/semi-insulating GaAs contact
Journal of Applied Physics, 1995Co-Authors: T. P. Chen, S. Fung, C. D. BelingAbstract:For nickel on the chemically clean surface of undoped semi‐insulating GaAs at room temperature, an upward surface band bending of 0.062 eV and a barrier height of 0.690 eV have been observed by the photovoltage and the internal photoemission techniques, respectively. The observed surface band bending is in excellent agreement with its predicted value, and the observed barrier height also agrees very well with its value from the very careful analysis of reversed I‐V data. It has been determined that the interfacial Fermi level lies at 0.690 eV below the GaAs conduction band minimum at the interface. The interfacial Fermi level is found to coincide with the energy level of the EL2 Native Defect, indicating the importance of the EL2 in the Fermi level pinning at the interface.
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Interfacial Fermi level and surface band bending in Ni/semi‐insulating GaAs contact
Journal of Applied Physics, 1995Co-Authors: T. P. Chen, Y. C. Liu, S. Fung, C. D. BelingAbstract:For nickel on the chemically clean surface of undoped semi‐insulating GaAs at room temperature, an upward surface band bending of 0.062 eV and a barrier height of 0.690 eV have been observed by the photovoltage and the internal photoemission techniques, respectively. The observed surface band bending is in excellent agreement with its predicted value, and the observed barrier height also agrees very well with its value from the very careful analysis of reversed I‐V data. It has been determined that the interfacial Fermi level lies at 0.690 eV below the GaAs conduction band minimum at the interface. The interfacial Fermi level is found to coincide with the energy level of the EL2 Native Defect, indicating the importance of the EL2 in the Fermi level pinning at the interface.
Marek Pruski - One of the best experts on this subject based on the ideXlab platform.
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on the nature of the Native Defect esr in thin diamond films
MRS Proceedings, 1994Co-Authors: J Shinar, H Jia, D P Lang, Marek PruskiAbstract:The X-band ESR of thin diamond films deposited from 99.5% H 2 /0.5% CH 4 is compared to that of films similarly prepared from D 2 CD 4 and H 2 / 13 CH 4 . The main line and the satellites at ±7.2 G are unaffected by annealing at T 13 C spin-lattice relaxation rate, which indicates that the distribution of paramagnetic centers is homogeneous to within ∼0.04 μm. However, they may be nonuniformly distributed on a finer scale, consistent with the concentrations in m ulti vacancies or stacking faults recently suggested by Fanciulli and Moustakas.
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nature of the Native Defect esr and hydrogen dangling bond centers in thin diamond films
Physical Review B, 1993Co-Authors: H Jia, J Shinar, D P Lang, Marek PruskiAbstract:The [ital X]-band ESR of thin diamond films deposited from a mixture of 99.5% H[sub 2] and 0.5% CH[sub 4] is compared to those of films similarly prepared from D[sub 2]-CD[sub 4] and H[sub 2]-[sup 13]CH[sub 4] mixtures. Main line and satellites at [plus minus]7.2 G are unaffected by annealing at [ital T][le]1100 [degree]C, but their intensity is reduced upon annealing at [similar to]1500 [degree]C. Since the satellites are absent from the deuterated films, they are attributed to newly identified dangling-bond H centers, possibly on internal surfaces, but more plausibly embedded in the bulk. This is consistent with the [sup 13]C relaxation rate, which indicates a uniform distribution of paramagnetic centers.
T. P. Chen - One of the best experts on this subject based on the ideXlab platform.
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Interfacial Fermi level and surface band bending in Ni/semi-insulating GaAs contact
Journal of Applied Physics, 1995Co-Authors: T. P. Chen, S. Fung, C. D. BelingAbstract:For nickel on the chemically clean surface of undoped semi‐insulating GaAs at room temperature, an upward surface band bending of 0.062 eV and a barrier height of 0.690 eV have been observed by the photovoltage and the internal photoemission techniques, respectively. The observed surface band bending is in excellent agreement with its predicted value, and the observed barrier height also agrees very well with its value from the very careful analysis of reversed I‐V data. It has been determined that the interfacial Fermi level lies at 0.690 eV below the GaAs conduction band minimum at the interface. The interfacial Fermi level is found to coincide with the energy level of the EL2 Native Defect, indicating the importance of the EL2 in the Fermi level pinning at the interface.
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Interfacial Fermi level and surface band bending in Ni/semi‐insulating GaAs contact
Journal of Applied Physics, 1995Co-Authors: T. P. Chen, Y. C. Liu, S. Fung, C. D. BelingAbstract:For nickel on the chemically clean surface of undoped semi‐insulating GaAs at room temperature, an upward surface band bending of 0.062 eV and a barrier height of 0.690 eV have been observed by the photovoltage and the internal photoemission techniques, respectively. The observed surface band bending is in excellent agreement with its predicted value, and the observed barrier height also agrees very well with its value from the very careful analysis of reversed I‐V data. It has been determined that the interfacial Fermi level lies at 0.690 eV below the GaAs conduction band minimum at the interface. The interfacial Fermi level is found to coincide with the energy level of the EL2 Native Defect, indicating the importance of the EL2 in the Fermi level pinning at the interface.
H Sitter - One of the best experts on this subject based on the ideXlab platform.
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doping of zinc selenide telluride
Applied Physics Letters, 1994Co-Authors: W Faschinger, S O Ferreira, H SitterAbstract:We investigate the doping behavior of ZnSe/ZnTe short period superlattices. p‐type doping is achieved with a dc nitrogen plasma source, n‐type doping with chlorine from a ZnCl2 Knudsen source. Even a small Te content has a strong positive effect on p doping: Doping levels in the upper 1019 cm−3 range are achieved, and ohmic contacts can be obtained even for low carrier concentrations. The data are in excellent agreement with a theory based on the amphoteric Native Defect model. The opposite is valid for n doping: At Te concentrations above 20% electron concentrations are below 1016 cm−3. As a possible way to get both good n‐ and p‐type doping at the same lattice constant we propose the use of the quaternary compound Zn(1−y)Mg(y)Se(1−x)Te(x).