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James S Speck - One of the best experts on this subject based on the ideXlab platform.

  • intervalley energy of gan Conduction Band measured by femtosecond pump probe spectroscopy
    Physical Review B, 2016
    Co-Authors: Saulius Marcinkevicius, Tomas Kristijonas Uždavinys, Humberto M Foronda, Daniel A Cohen, C Weisbuch, James S Speck
    Abstract:

    Time-resolved transmission and reflection measurements were performed for bulk GaN at room temperature to evaluate the energy of the first Conduction Band satellite valley. The measurements showed ...

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in ...

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in good agreement with values inferred from a number of optical experiments.

H Zhang - One of the best experts on this subject based on the ideXlab platform.

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in ...

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in good agreement with values inferred from a number of optical experiments.

Takashi Minemoto - One of the best experts on this subject based on the ideXlab platform.

  • effect of the Conduction Band offset on interfacial recombination behavior of the planar perovskite solar cells
    Nano Energy, 2018
    Co-Authors: Takashi Minemoto, Chao Ding, Yaohong Zhang, Feng Liu, Yukiko Kitabatake, Shuzi Hayase, Taro Toyoda, Kenji Yoshino, Kenji Katayama
    Abstract:

    Abstract The effects of the Conduction Band offset (CBO) between the electron selective layer (ESL) and the perovskite layer in planar-heterojunction perovskite solar cells (PSCs) have been systematically investigated for the first time. To obtain different values of CBO, Magnesium doped zinc oxide (Zn1-xMgxO (ZMO)) thin films with a tunable Conduction Band energy level were employed as a model ESL in planar PSCs. We found that the charge recombination at the interface between the ESL and perovskite is strongly dependent on the CBO values: When the cliff structure is formed, i.e., when the Conduction Band minimum (CBM) of the ESL is lower than that of the perovskite, the interface recombination became dominant, and the open-circuit voltage (Voc) worsened. When the spike structure is formed, i.e., when the CBM of the ESL is higher than that of the perovskite, the interfacial recombination is largely suppressed, which leads to an increased Voc of the solar cells. Additionally, we found that an appropriate amount of Mg doping in ZnO to form ZMO reduced carrier concentration and improved carrier mobility, thereby enhancing the charge collection efficiency of the photoexcited electrons by the FTO electrode and, consequently, the short-circuit current density (Jsc). Using transient absorption (TA) measurements, we have revealed for the first time that the electron injection from photoexcited MAPbI3 to FTO through a ZMO compact layer occurs in the timescale of a few nanoseconds in planar PSCs. PSCs based on the optimized Zn0.9Mg0.1O-ESL exhibited a considerable increase (~ 35%) in power conversion efficiencies (PCE) compared with that of the control device.

  • control of Conduction Band offset in wide gap cu in ga se solar cells
    Solar Energy Materials and Solar Cells, 2003
    Co-Authors: Takashi Minemoto, Yasuhiro Hashimoto, Takuya Satoh, Takayuki Negami, Hideyuki Takakura, Wahid Shamskolahi, Yoshihiro Hamakawa
    Abstract:

    The effects of Conduction Band offset of window/Cu(In,Ga)Se 2 (CIGS) layers in wide-gap CIGS based solar cells are investigated. In order to control the Conduction Band offset, a Zn 1 - x Mg x O film was utilized as the window layer. We fabricated CIGS solar cells consisting of an ITO/Zn 1 - x Mg x O/CdS/CIGS/Mo/glass structure with various CIGS Band gaps (Eg 0.97-1.43 eV). The solar cells with CIGS Band gaps wider than 1.15 eV showed higher open circuit voltages and fill factors than those of conventional ZnO/CdS/CIGS solar cells. The improvement is attributed to the reduction of the CdS/CIGS interface recombination, and it is also supported by the theoretical analysis using device simulation.

  • cu in ga se2 solar cells with controlled Conduction Band offset of window cu in ga se2 layers
    Journal of Applied Physics, 2001
    Co-Authors: Takashi Minemoto, Yasuhiro Hashimoto, Takuya Satoh, Takayuki Negami, Hideyuki Takakura, Yoshihiro Hamakawa
    Abstract:

    Our group studied the effects of Conduction Band offset of window/Cu(In,Ga)Se2 (CIGS) layers on CIGS-based solar cell performance. To control the Conduction Band offset, we considered the use of a window layer of Zn1−xMgxO thin film with a controllable Band gap as an alternative to the conventional window layer using CdS film. From the measurement of valence Band offset between Zn1−xMgxO/CIGS layers and the Band gap of each layer, we confirmed that the Conduction Band offset of Zn1−xMgxO/CIGS layers could be controlled by changing the Mg content of the Zn1−xMgxO film. The CIGS-based solar cells prepared for this study consisted of an ITO/Zn1−xMgxO/CIGS/Mo/soda-lime glass structure. When the Conduction Band minimum of Zn1−xMgxO was higher than that of CIGS, the performance of CIGS-based solar cells with a Zn1−xMgxO window layer was equivalent to that of CIGS-based solar cells with CdS window layers. We confirmed that the control of the Conduction Band offset of the window/CIGS layers decreases the majority...

  • theoretical analysis of the effect of Conduction Band offset of window cis layers on performance of cis solar cells using device simulation
    Solar Energy Materials and Solar Cells, 2001
    Co-Authors: Takashi Minemoto, Yasuhiro Hashimoto, Takayuki Negami, Hideyuki Takakura, Yoshihiro Hamakawa, Takuya Matsui, Takeshi Uenoyama, Masatoshi Kitagawa
    Abstract:

    Abstract One of the most important factors of CdS leading to high performance in Cu(In,Ga)Se 2 (CIGS) solar cells is appropriation of the Conduction Band offset of CdS/CIGS layers. However, it is not clearly explained. In this study, device modeling and simulation were conducted to explain the effect of Conduction Band offset of window/CIGS layers on performance of CIGS solar cells. As a result of calculation, excellent performance can be obtained when the Conduction Band of window layer positions higher by 0–0.4 eV than that of CIGS.

C Poblenz - One of the best experts on this subject based on the ideXlab platform.

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in ...

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in good agreement with values inferred from a number of optical experiments.

E J Miller - One of the best experts on this subject based on the ideXlab platform.

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in ...

  • measurement of polarization charge and Conduction Band offset at inxga1 xn gan heterojunction interfaces
    Applied Physics Letters, 2004
    Co-Authors: H Zhang, E J Miller, C Poblenz, James S Speck
    Abstract:

    The spontaneous and piezoelectric polarization fields in group-III nitride semiconductors lead to the presence of large electrostatic sheet charge densities at nitride semiconductor heterojunction interfaces. Precise quantitative knowledge of these polarization-induced charge densities and of the Band-edge discontinuities at nitride heterojunction interfaces is therefore essential in nitride semiconductor device design and analysis. We have used capacitance–voltage profiling to measure the Conduction-Band offset and polarization charge density at InxGa1−xN/GaN heterojunction interfaces with x=0.054 and x=0.09. We obtain Conduction-Band offsets ΔEC=0.09±0.07 eV for x=0.054 and ΔEC=0.22±0.05 eV for x=0.09, corresponding to an averaged Conduction-to-valence-Band offset ratio ΔEC:ΔEV of 58:42. Our measurements yield polarization charge densities of (1.80±0.32)×1012 e/cm2 for x=0.054 and (4.38±0.36)×1012 e/cm2 for x=0.09. These values are smaller than those predicted by recent theoretical calculations, but in good agreement with values inferred from a number of optical experiments.