The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Joel Cibert - One of the best experts on this subject based on the ideXlab platform.
-
Spin susceptibility enhancement in a two-dimensional Hole Gas
Physical Review B, 2006Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, F. Perez, Bernard Jusserand, Joel CibertAbstract:The critical spin splitting needed to fully polarize a two-dimensional heavy-Hole Gas in a (Cd,Mn)Te quantum well thanks to the giant Zeeman effect is measured through photoluminescence and transmission spectroscopy. While the splitting between two circularly polarized peaks in photoluminescence remains equal to the bare spin splitting, the critical spin splitting which governs the polarization is enhanced, in good agreement with the prediction of a model of Hole-Hole interactions previously applied to conduction electrons. Consequences for carrier-induced ferromagnetism are discussed.
-
Spin susceptibility enhancement in a two-dimensional Hole Gas
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2006Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, F. Perez, Bernard Jusserand, Joel CibertAbstract:The critical spin splitting needed to fully polarize a two-dimensional heavy-Hole Gas in a (Cd,Mn)Te quantum well thanks to the giant Zeeman effect is measured through photoluminescence and transmission spectroscopy. While the splitting between two circularly polarized photoluminescence remains equal to the bare spin splitting, the critical spin splitting which governs the polarization is enhanced, in good agreement with the prediction of a model of Hole-Hole interactions previously applied to conduction electrons. Consequences for carrier induced ferromagnetism are discussed.
-
Spectroscopy and Characteristic Energies of a Spin‐Polarized Hole Gas
AIP Conference Proceedings, 2005Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, Joel Cibert, M. Bertolini, Serge Tatarenko, J. A. GajAbstract:The giant Zeeman splitting present in a quantum well made of a diluted magnetic semiconductor allows us not only to completely polarize the Hole Gas it contains, but also to destabilize the charged exciton singlet state (which emits at small spin splitting) in favor of an electron‐Hole state involving a majority‐spin Hole. At low carrier density, this is the neutral exciton, and at higher carrier density, a weakly correlated electron‐Hole pair. By comparing spectra recorder under different conditions, we access different characteristic energies such as the true binding energy of the charged exciton, the spin splitting necessary to fully polarize the Hole Gas, and the energy of excited states of the Hole Gas which are involved in optical transitions.
-
Ferromagnetic transition induced by a two-dimensional Hole Gas in a semimagnetic quantum well
Journal of Crystal Growth, 1998Co-Authors: Joel Cibert, Piotr Kossacki, A. Haury, A. Wasiela, Y. Merle D'aubigné, Tomasz Dietl, Alexandre Arnoult, Serge TatarenkoAbstract:The presence of a ferromagnetic transition in single, modulation-doped quantum wells of Cd 1 - x Mn x Te/ Cd 1-y-z Mg y Zn z Te : N is evidenced by magnetospectroscopy. The transition is driven by long-range RKKY interaction between the Mn spins, mediated by the two-dimensional Hole Gas. Magneto-optic data are well described in terms of a mean-field model. The value of the exchange-field induced by the spin-polarized Hole Gas is determined. We show that the zero-field splitting which characterizes the ferromagnetic order contains both a p-d exchange term and a contribution due to Hole Hole exchange interactions. The initial Hole polarization is only partial and increases slowly when the temperature is reduced further below the transition.
Y Shiraki - One of the best experts on this subject based on the ideXlab platform.
-
cubic rashba spin orbit interaction of a two dimensional Hole Gas in a strained ge sige quantum well
Physical Review Letters, 2014Co-Authors: Rai Moriya, K. Sawano, Y Shiraki, Yusuke Hoshi, Satoru Masubuchi, Andreas Wild, Christian Neumann, G AbstreiterAbstract:The spin-orbit interaction (SOI) of a two-dimensional Hole Gas in the inversion symmetric semiconductor Ge is studied in a strained-Ge/SiGe quantum well structure. We observe weak antilocalization (WAL) in the magnetoconductivity measurement, revealing that the WAL feature can be fully described by the k-cubic Rashba SOI theory. Furthermore, we demonstrate electric field control of the Rashba SOI. Our findings reveal that the heavy Hole (HH) in strained Ge is a purely cubic Rashba system, which is consistent with the spin angular momentum m_{j}=±3/2 nature of the HH wave function.
-
upper limit of two dimensional Hole Gas mobility in strained ge sige heterostructures
Applied Physics Letters, 2012Co-Authors: T Tanaka, K. Sawano, Y Shiraki, Yusuke Hoshi, Noritaka Usami, Kohei M ItohAbstract:High two-dimensional Hole Gas (2DHG) mobility (μ2DHG>10000cm2/Vs at T 5000cm2/Vs at room temperature is presented.
-
observation of pronounced effect of compressive strain on room temperature transport properties of two dimensional Hole Gas in a strained ge quantum well
Applied Physics Express, 2008Co-Authors: Maksym Myronov, K. Sawano, Kohei M Itoh, Y ShirakiAbstract:Strong effect of compressive strain on room-temperature transport properties of two-dimensional Hole Gas (2DHG) confined in a strained Ge quantum well (QW) of SiGe heterostructures was observed. By increasing compressive strain in the Ge QW the pronounced increase of 2DHG Gas density and conductivity were obtained in the full range of researched strain variation. At the same time the increase of 2DHG drift mobility was observed until a certain high strain in the Ge QW, but showed slight reduction under higher strain. Nevertheless the monotonous enhancement of 2DHG conductivity was observed.
-
observation of two dimensional Hole Gas with mobility and carrier density exceeding those of two dimensional electron Gas at room temperature in the sige heterostructures
Applied Physics Letters, 2007Co-Authors: Maksym Myronov, K. Sawano, Y Shiraki, T Mouri, Kohei M ItohAbstract:Very high two-dimensional Hole Gas (2DHG) drift mobility of 3100cm2∕Vs is obtained at extremely high density of 41×1011cm−2 in the modulation doped, 20nm thick, strained Ge quantum well (QW) of SiGe heterostructure at room temperature. Very high 2DHG density is achieved by increasing the boron modulation doping, reducing the spacer layer thickness located between it and Ge QW, and increasing the valence-band offset of Ge QW, which also results in the enhancement of mobility. The obtained 2DHG mobility and carrier density exceed those reported for two-dimensional electron Gas in the strained Si QW of SiGe heterostructures.
Debdeep Jena - One of the best experts on this subject based on the ideXlab platform.
-
a polarization induced 2d Hole Gas in undoped gallium nitride quantum wells
Science, 2019Co-Authors: Reet Chaudhuri, Samuel James Bader, Zhen Chen, David A Muller, Huili Grace Xing, Debdeep JenaAbstract:A high-conductivity two-dimensional (2D) Hole Gas, analogous to the ubiquitous 2D electron Gas, is desirable in nitride semiconductors for wide-bandgap p-channel transistors. We report the observation of a polarization-induced high-density 2D Hole Gas in epitaxially grown gallium nitride on aluminium nitride and show that such Hole Gases can form without acceptor dopants. The measured high 2D Hole Gas densities of about 5 × 1013 per square centimeters remain unchanged down to cryogenic temperatures and allow some of the lowest p-type sheet resistances among all wide-bandgap semiconductors. The observed results provide a probe for studying the valence band structure and transport properties of wide-bandgap nitride interfaces.
-
A polarization-induced 2D Hole Gas in undoped gallium nitride quantum wells
Science (New York N.Y.), 2019Co-Authors: Reet Chaudhuri, Samuel James Bader, Zhen Chen, David A Muller, Huili, Xing, Debdeep JenaAbstract:The long-missing polarization-induced two-dimensional Hole Gas is finally observed in undoped gallium nitride quantum wells. Experimental results provide unambiguous proof that a 2D Hole Gas in GaN grown on AlN does not need acceptor doping, and can be formed entirely by the difference in the internal polarization fields across the semiconductor heterojunction. The measured 2D Hole Gas densities, about $4 \times 10^{13}$ cm$^{-2}$, are among the highest among all known semiconductors and remain unchanged down to cryogenic temperatures. Some of the lowest sheet resistances of all wide-bandgap semiconductors are seen. The observed results provide a new probe for studying the valence band structure and transport properties of wide-bandgap nitride interfaces, and simultaneously enable the missing component for gallium nitride-based p-channel transistors for energy-efficient electronics.
-
Wurtzite phonons and the mobility of a GaN/AlN 2D Hole Gas
Applied Physics Letters, 2019Co-Authors: Samuel James Bader, Reet Chaudhuri, Huili Grace Xing, Martin F. Schubert, Han Wui Then, Debdeep JenaAbstract:To make complementary GaN electronics a desirable technology, it is essential to understand the low mobility of 2D Hole Gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D Hole Gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D Hole Gas are examined and a means is proposed to engineer the strain to improve the 2D Hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.To make complementary GaN electronics a desirable technology, it is essential to understand the low mobility of 2D Hole Gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D Hole Gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D Hole Gas are examined and a means is proposed to engineer the strain to improve the 2D Hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.
-
wurtzite phonons and the mobility of a gan aln 2d Hole Gas
Applied Physics Letters, 2019Co-Authors: Samuel James Bader, Reet Chaudhuri, Huili Grace Xing, Martin F. Schubert, Han Wui Then, Debdeep JenaAbstract:To make complementary GaN electronics a desirable technology, it is essential to understand the low mobility of 2D Hole Gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D Hole Gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D Hole Gas are examined and a means is proposed to engineer the strain to improve the 2D Hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.To make complementary GaN electronics a desirable technology, it is essential to understand the low mobility of 2D Hole Gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D Hole Gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D Hole Gas are examined and a means is proposed to engineer the strain to improve the 2D Hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.
-
wurtzite phonons and the mobility of a gan aln 2d Hole Gas
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Samuel James Bader, Reet Chaudhuri, Huili Grace Xing, Martin F. Schubert, Han Wui Then, Debdeep JenaAbstract:To make complementary GaN electronics more than a pipe dream, it is essential to understand the low mobility of 2D Hole Gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D Hole Gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D Hole Gas are examined and a means is proposed to engineer the strain to improve the 2D Hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.
Hervé Boukari - One of the best experts on this subject based on the ideXlab platform.
-
Spin susceptibility enhancement in a two-dimensional Hole Gas
Physical Review B, 2006Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, F. Perez, Bernard Jusserand, Joel CibertAbstract:The critical spin splitting needed to fully polarize a two-dimensional heavy-Hole Gas in a (Cd,Mn)Te quantum well thanks to the giant Zeeman effect is measured through photoluminescence and transmission spectroscopy. While the splitting between two circularly polarized peaks in photoluminescence remains equal to the bare spin splitting, the critical spin splitting which governs the polarization is enhanced, in good agreement with the prediction of a model of Hole-Hole interactions previously applied to conduction electrons. Consequences for carrier-induced ferromagnetism are discussed.
-
Spin susceptibility enhancement in a two-dimensional Hole Gas
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2006Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, F. Perez, Bernard Jusserand, Joel CibertAbstract:The critical spin splitting needed to fully polarize a two-dimensional heavy-Hole Gas in a (Cd,Mn)Te quantum well thanks to the giant Zeeman effect is measured through photoluminescence and transmission spectroscopy. While the splitting between two circularly polarized photoluminescence remains equal to the bare spin splitting, the critical spin splitting which governs the polarization is enhanced, in good agreement with the prediction of a model of Hole-Hole interactions previously applied to conduction electrons. Consequences for carrier induced ferromagnetism are discussed.
-
Spectroscopy and Characteristic Energies of a Spin‐Polarized Hole Gas
AIP Conference Proceedings, 2005Co-Authors: Hervé Boukari, Piotr Kossacki, David Ferrand, Joel Cibert, M. Bertolini, Serge Tatarenko, J. A. GajAbstract:The giant Zeeman splitting present in a quantum well made of a diluted magnetic semiconductor allows us not only to completely polarize the Hole Gas it contains, but also to destabilize the charged exciton singlet state (which emits at small spin splitting) in favor of an electron‐Hole state involving a majority‐spin Hole. At low carrier density, this is the neutral exciton, and at higher carrier density, a weakly correlated electron‐Hole pair. By comparing spectra recorder under different conditions, we access different characteristic energies such as the true binding energy of the charged exciton, the spin splitting necessary to fully polarize the Hole Gas, and the energy of excited states of the Hole Gas which are involved in optical transitions.
Charles M. Lieber - One of the best experts on this subject based on the ideXlab platform.
-
highly transparent contacts to the 1d Hole Gas in ultrascaled ge si core shell nanowires
ACS Nano, 2019Co-Authors: Masiar Sistani, Jovian Delaforce, R B G Kramer, Nicolas Roch, Minh Anh Luong, Martien Den Hertog, Eric Robin, J Smoliner, Jun Yao, Charles M. LieberAbstract:Semiconductor-superconductor hybrid systems have outstanding potential for emerging high-performance nanoelectronics and quantum devices. However, critical to their successful application is the fabrication of high-quality and reproducible semiconductor-superconductor interfaces. Here, we realize and measure axial Al-Ge-Al nanowire heterostructures with atomically precise interfaces, enwrapped by an ultrathin epitaxial Si layer further denoted as Al-Ge/Si-Al nanowire heterostructures. The heterostructures were synthesized by a thermally induced exchange reaction of single-crystalline Ge/Si core/shell nanowires and lithographically defined Al contact pads. Applying this heterostructure formation scheme enables self-aligned quasi one-dimensional crystalline Al leads contacting ultrascaled Ge/Si segments with contact transparencies greater than 96%. Integration into back-gated field-effect devices and continuous scaling beyond lithographic limitations allows us to exploit the full potential of the highly transparent contacts to the 1D Hole Gas at the Ge-Si interface. This leads to the observation of ballistic transport as well as quantum confinement effects up to temperatures of 150 K. Low-temperature measurements reveal proximity-induced superconductivity in the Ge/Si core/shell nanowires. The realization of a Josephson field-effect transistor allows us to study the subgap structure caused by multiple Andreev reflections. Most importantly, the absence of a quantum dot regime indicates a hard superconducting gap originating from the highly transparent contacts to the 1D Hole Gas, which is potentially interesting for the study of Majorana zero modes. Moreover, underlining the importance of the proposed thermally induced Al-Ge/Si-Al heterostructure formation technique, our system could contribute to the development of key components of quantum computing such as gatemon or transmon qubits.
-
one dimensional Hole Gas in germanium silicon nanowire heterostructures
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: J Xiang, Brian P. Timko, Charles M. LieberAbstract:Two-dimensional electron and Hole Gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or Hole Gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the synthesis and transport studies of a 1D Hole Gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure. Room temperature electrical transport measurements clearly show Hole accumulation in undoped Ge/Si nanowire heterostructures, in contrast to control experiments on single-component nanowires. Low-temperature studies show well-controlled Coulomb blockade oscillations when the Si shell serves as a tunnel barrier to the Hole Gas in the Ge channel. Transparent contacts to the Hole Gas also have been reproducibly achieved by thermal annealing. In such devices, we observe conductance quantization at low temperatures, corresponding to ballistic transport through 1D subbands, where the measured subband energy spacings agree with calculations for a cylindrical confinement potential. In addition, we observe a “0.7 structure,” which has been attributed to spontaneous spin polarization, suggesting the universality of this phenomenon in interacting 1D systems. Lastly, the conductance exhibits little temperature dependence, consistent with our calculation of reduced backscattering in this 1D system, and suggests that transport is ballistic even at room temperature.
-
One-dimensional Hole Gas in germanium/silicon nanowire heterostructures
Proceedings of the National Academy of Sciences, 2005Co-Authors: W Lu, Brian P. Timko, J Xiang, Charles M. LieberAbstract:Two-dimensional electron and Hole Gas systems, enabled through band structure design and epitaxial growth on planar substrates, have served as key platforms for fundamental condensed matter research and high-performance devices. The analogous development of one-dimensional (1D) electron or Hole Gas systems through controlled growth on 1D nanostructure substrates, which could open up opportunities beyond existing carbon nanotube and nanowire systems, has not been realized. Here, we report the synthesis and transport studies of a 1D Hole Gas system based on a free-standing germanium/silicon (Ge/Si) core/shell nanowire heterostructure. Room temperature electrical transport measurements clearly show Hole accumulation in undoped Ge/Si nanowire heterostructures, in contrast to control experiments on single-component nanowires. Low-temperature studies show well-controlled Coulomb blockade oscillations when the Si shell serves as a tunnel barrier to the Hole Gas in the Ge channel. Transparent contacts to the Hole Gas also have been reproducibly achieved by thermal annealing. In such devices, we observe conductance quantization at low temperatures, corresponding to ballistic transport through 1D subbands, where the measured subband energy spacings agree with calculations for a cylindrical confinement potential. In addition, we observe a “0.7 structure,” which has been attributed to spontaneous spin polarization, suggesting the universality of this phenomenon in interacting 1D systems. Lastly, the conductance exhibits little temperature dependence, consistent with our calculation of reduced backscattering in this 1D system, and suggests that transport is ballistic even at room temperature.