Pb1-xSnxSe: a new tunable topological platform with terahertz band gap
Terahertz Emitters, Receivers, and Applications X, 2019
In a topological crystalline insulator such as Pb1-xSnxSe, massless Dirac states emerge at an int... more In a topological crystalline insulator such as Pb1-xSnxSe, massless Dirac states emerge at an interface with a trivial insulator. We demonstrate the great versatility of Pb1-xSnxSe electronic properties, which makes it a highly promising material to control the massless Dirac states emerging from topological properties. Using magnetooptical transmission spectroscopy on high quality molecular beam epitaxy grown Pb1-xSnxSe, we probe the variation of its bulk energy gap versus chemical composition, temperature, and strain. The determination of its bulk electronic properties will be of critical relevance to design heterostructures. A magneto-optical study on PbSnSe/PbEuSe superlattices will allow us to characterize the topological interface states occurring at each interface, as well as their tunability versus temperature. The engineering of these massless states is shown to be a promising route to achieve photo detection and photoemission in the terahertz range.
One of the limiting factors in the performance of future CMOS integrated circuits is the low hole... more One of the limiting factors in the performance of future CMOS integrated circuits is the low hole mobility which causes the transconductance of p-channel transistors to be inferior to those of n-channel devices. One promising way of enhancing hole mobility is to introduce a buried SiGe layer under the gate of p-MOS transistors. The mobility improvement thus results from, i) reduction in surface scattering (by moving carriers away from scattering sites at the Si/SiO2 interface), and ii) higher in-plane hole mobility in biaxally strained SiGe layers.
Microwave photoconductivity experiments on size-tunable field-effect confined antidots provide th... more Microwave photoconductivity experiments on size-tunable field-effect confined antidots provide the dependance of the low-energy excitation (magnetoplasmons around antidots) as a function of the gate voltage. The influence of the electron density and the antidot size on the magnetoplasmon mode can be analyzed using the theory recently developed by Mikhaiqov and Volkov.
The European Physical Journal B - Condensed Matter, 2003
We investigate the FIR magneto-optical transitions in doped self-assembled InAs quantum dots with... more We investigate the FIR magneto-optical transitions in doped self-assembled InAs quantum dots with an average filling ranging from 0.6 to 6 electrons per dot. Significant changes in the magnetic field dispersion, the line-width and the amplitude of the transitions are observed as the doping level is varied, in agreement with our theoretical calculations. We show that our technique is an effective tool to obtain informations regarding the dot size homogeneity and the electron filling uniformity.
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface state... more Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSnxTe. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb1−xSnxSe and Pb1−xSnxTe ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb1−xSnxSe and Pb1−xSnxTe for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the to...
We report on magnetotunneling studies in a pseudomorphic In 0:1 Ga 0:9 As/AlAs/GaAs structure in ... more We report on magnetotunneling studies in a pseudomorphic In 0:1 Ga 0:9 As/AlAs/GaAs structure in a magnetic elds perpendicular or tilted to the tunneling current. In a transverse magnetic eld, we h a ve observed a shift to higher voltages and a strong broadening of resonant peak in I(V) characteristics. These features are explained by the action of the Lorentz force coupling the parallel and perpendicular motions. In a tilted magnetic eld, we h a ve observed structures in I(V) characteristics which corresponds to tunneling in the prewell to the midwell with non-conservation of Landau level index in good agreement with a coherent model in which the e ect of the transverse component is treated in a perturbation approach.
Optical Characterization of III-V and II-VI Semiconductor Heterolayers
Advances in Electronics and Electron Physics, 1988
Publisher Summary There is an explosive increase in the research activities on semiconductor hete... more Publisher Summary There is an explosive increase in the research activities on semiconductor heterolayers. The diversity of available heterolayers has considerably increased owing to the dissemination and increased mastery of modern growth techniques such as Molecula Beam Epitaxy (M.B.E.) or Metal Organic Chemical Vapor Deposition (M.O.C.V.D.). The successful growth of strained layer materials relaxes the severe constraint of choosing lattice-matched semiconductors as possible hosts for the heterolayers and therefore multiplies the number of available heterostructures in a considerable way. To the III-V heterolayers, one should add II-VI's either with a narrow bandgap or a wide bandgap such as Cdl–xMnxTe-CdTe. This chapter presents a survey of some basic optical data obtained on a variety of III-V and II-VI heterolayers. This chapter focuses the attention on characterization purposes and therefore discusses only absorption and photoluminescence data.
Low-temperature investigations of the quantum Hall effect in In_{x} Ga_{1-x} As-InP heterojunctions
Physical Review B, 1983
... in In,,Ga1_,,As—InP heterojunctions A. Briggs CR TBT and SNCI, CNRS, 38042 Grenoble, France Y... more ... in In,,Ga1_,,As—InP heterojunctions A. Briggs CR TBT and SNCI, CNRS, 38042 Grenoble, France Y. Guldner, JP Vieren, and M. Voos Groupe de Physique des Solides, Laborazoire associé au CNRS, de I 'Eco1e Normale Supérieure, 24 rue Lhomond, 75005 Paris, France JP ...
Infrared absorption has been investigated in high quality p-type SiGe/Si multiple quantum wells g... more Infrared absorption has been investigated in high quality p-type SiGe/Si multiple quantum wells grown by UHV-CVD. Both intersubband and free carrier absorptions have been quantitatively analysed using calculations of the intersubband absorption coefficient in the envelope function formalism and a Drude model to account for the free carrier effects. Their dependence with polarization, doping level and Ge content are presented.
Far-infrared magnetospectroscopy of polaron states in self-assembled InAs/GaAs quantum dots
Physical Review B, 2002
We investigate the far infrared magneto-optical transitions in self-assembled InAs quantum dots w... more We investigate the far infrared magneto-optical transitions in self-assembled InAs quantum dots with different lateral diameters and we show that a purely electronic model is unable to account for the experimental data. We calculate the coupling between the mixed electron-LO-phonon states using the Fröhlich Hamiltonian, from which we determine the polaron states as well as the energies of the dipolar
35th International Conference on Infrared, Millimeter, and Terahertz Waves, 2010
A THz quantum cascade structure has been designed to allow population relaxation between crossing... more A THz quantum cascade structure has been designed to allow population relaxation between crossing Landau levels from different subbands under perpendicular magnetic field. Electroluminescence measurements show intersubband luminescence as well as inter-Landau level emission (cyclotron emission).
Low-temperature infrared magnetoabsorption experiments were carried out on Hgl kMn~Te mixed cryst... more Low-temperature infrared magnetoabsorption experiments were carried out on Hgl kMn~Te mixed crystals with compositions corresponding to the semiconducting (positive energy gap) range. Measurements were performed in the spectral region 100-350 meV in Voigt and Faraday geometries, using both linear and circular polarizations. The magneto-optical data provide observation of interband I 8~I 6 transitions. In addition, transitions from acceptor levels to I 6 Landau levels were observed. The interband magneto-optical transitions are interpreted within the framework of the Pidgeon-Brown model, modified by the contributions of the s-d and p-d spin-spin exchange interaction between band electrons and localized Mn~+ spins. From the theoretical fits of the transition energies to the observed absorption lines, the relative magnetization A (H, T) is deduced at T = 4.2 and 2 K for alloys of various Mn content. In contrast with zero-gap Hgl kMnk Te, in the present case 3 (H, T) exhibits a nearly linear magnetic field dependence and depends only weakly on temperature. These features are related to the strong antiferromagnetic interactions between the localized magnetic moments, Conduction electrons in crystals in this composition range exhibit large and positive g factors as a consequence of the s-d exchange coupling.
When a Dirac fermion system acquires an energy-gap, it is said to have either trivial (positive e... more When a Dirac fermion system acquires an energy-gap, it is said to have either trivial (positive energy-gap) or non-trivial (negative energy-gap) topology, depending on the parity ordering of its conduction and valence bands. The non-trivial regime is identified by the presence of topological surface or edge-states dispersing in the energy gap of the bulk and is attributed a non-zero topological index. In this work, we show that such topological indices can be determined experimentally via an accurate measurement of the effective velocity of bulk massive Dirac fermions. We demonstrate this approach analytically starting from the Bernevig-Hughes-Zhang Hamiltonian to show how the topological index depends on this velocity. We then experimentally extract the topological index in Pb 1-x Sn x Se and Pb 1-x Sn x Te using infrared magnetooptical Landau level spectroscopy. This approach is argued to be universal to all material classes that can be described by a Bernevig-Hughes-Zhang-like model and that host a topological phase transition.
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface state... more Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead-tin salts Pb 1−x Sn x Se and Pb 1−x Sn x Te. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb 1−x Sn x Se and Pb 1−x Sn x Te ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb 1−x Sn x Se and Pb 1−x Sn x Te for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the topological phase transition in TCI. We will finally present our views on prospects and open questions that have yet to be addressed in magneto-optical spectroscopy studies on Pb 1-x Sn x Se and Pb 1−x Sn x Te.
Pb1-xSnxSe: a new tunable topological platform with terahertz band gap
Terahertz Emitters, Receivers, and Applications X, 2019
In a topological crystalline insulator such as Pb1-xSnxSe, massless Dirac states emerge at an int... more In a topological crystalline insulator such as Pb1-xSnxSe, massless Dirac states emerge at an interface with a trivial insulator. We demonstrate the great versatility of Pb1-xSnxSe electronic properties, which makes it a highly promising material to control the massless Dirac states emerging from topological properties. Using magnetooptical transmission spectroscopy on high quality molecular beam epitaxy grown Pb1-xSnxSe, we probe the variation of its bulk energy gap versus chemical composition, temperature, and strain. The determination of its bulk electronic properties will be of critical relevance to design heterostructures. A magneto-optical study on PbSnSe/PbEuSe superlattices will allow us to characterize the topological interface states occurring at each interface, as well as their tunability versus temperature. The engineering of these massless states is shown to be a promising route to achieve photo detection and photoemission in the terahertz range.
One of the limiting factors in the performance of future CMOS integrated circuits is the low hole... more One of the limiting factors in the performance of future CMOS integrated circuits is the low hole mobility which causes the transconductance of p-channel transistors to be inferior to those of n-channel devices. One promising way of enhancing hole mobility is to introduce a buried SiGe layer under the gate of p-MOS transistors. The mobility improvement thus results from, i) reduction in surface scattering (by moving carriers away from scattering sites at the Si/SiO2 interface), and ii) higher in-plane hole mobility in biaxally strained SiGe layers.
Microwave photoconductivity experiments on size-tunable field-effect confined antidots provide th... more Microwave photoconductivity experiments on size-tunable field-effect confined antidots provide the dependance of the low-energy excitation (magnetoplasmons around antidots) as a function of the gate voltage. The influence of the electron density and the antidot size on the magnetoplasmon mode can be analyzed using the theory recently developed by Mikhaiqov and Volkov.
The European Physical Journal B - Condensed Matter, 2003
We investigate the FIR magneto-optical transitions in doped self-assembled InAs quantum dots with... more We investigate the FIR magneto-optical transitions in doped self-assembled InAs quantum dots with an average filling ranging from 0.6 to 6 electrons per dot. Significant changes in the magnetic field dispersion, the line-width and the amplitude of the transitions are observed as the doping level is varied, in agreement with our theoretical calculations. We show that our technique is an effective tool to obtain informations regarding the dot size homogeneity and the electron filling uniformity.
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface state... more Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSnxTe. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb1−xSnxSe and Pb1−xSnxTe ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb1−xSnxSe and Pb1−xSnxTe for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the to...
We report on magnetotunneling studies in a pseudomorphic In 0:1 Ga 0:9 As/AlAs/GaAs structure in ... more We report on magnetotunneling studies in a pseudomorphic In 0:1 Ga 0:9 As/AlAs/GaAs structure in a magnetic elds perpendicular or tilted to the tunneling current. In a transverse magnetic eld, we h a ve observed a shift to higher voltages and a strong broadening of resonant peak in I(V) characteristics. These features are explained by the action of the Lorentz force coupling the parallel and perpendicular motions. In a tilted magnetic eld, we h a ve observed structures in I(V) characteristics which corresponds to tunneling in the prewell to the midwell with non-conservation of Landau level index in good agreement with a coherent model in which the e ect of the transverse component is treated in a perturbation approach.
Optical Characterization of III-V and II-VI Semiconductor Heterolayers
Advances in Electronics and Electron Physics, 1988
Publisher Summary There is an explosive increase in the research activities on semiconductor hete... more Publisher Summary There is an explosive increase in the research activities on semiconductor heterolayers. The diversity of available heterolayers has considerably increased owing to the dissemination and increased mastery of modern growth techniques such as Molecula Beam Epitaxy (M.B.E.) or Metal Organic Chemical Vapor Deposition (M.O.C.V.D.). The successful growth of strained layer materials relaxes the severe constraint of choosing lattice-matched semiconductors as possible hosts for the heterolayers and therefore multiplies the number of available heterostructures in a considerable way. To the III-V heterolayers, one should add II-VI's either with a narrow bandgap or a wide bandgap such as Cdl–xMnxTe-CdTe. This chapter presents a survey of some basic optical data obtained on a variety of III-V and II-VI heterolayers. This chapter focuses the attention on characterization purposes and therefore discusses only absorption and photoluminescence data.
Low-temperature investigations of the quantum Hall effect in In_{x} Ga_{1-x} As-InP heterojunctions
Physical Review B, 1983
... in In,,Ga1_,,As—InP heterojunctions A. Briggs CR TBT and SNCI, CNRS, 38042 Grenoble, France Y... more ... in In,,Ga1_,,As—InP heterojunctions A. Briggs CR TBT and SNCI, CNRS, 38042 Grenoble, France Y. Guldner, JP Vieren, and M. Voos Groupe de Physique des Solides, Laborazoire associé au CNRS, de I 'Eco1e Normale Supérieure, 24 rue Lhomond, 75005 Paris, France JP ...
Infrared absorption has been investigated in high quality p-type SiGe/Si multiple quantum wells g... more Infrared absorption has been investigated in high quality p-type SiGe/Si multiple quantum wells grown by UHV-CVD. Both intersubband and free carrier absorptions have been quantitatively analysed using calculations of the intersubband absorption coefficient in the envelope function formalism and a Drude model to account for the free carrier effects. Their dependence with polarization, doping level and Ge content are presented.
Far-infrared magnetospectroscopy of polaron states in self-assembled InAs/GaAs quantum dots
Physical Review B, 2002
We investigate the far infrared magneto-optical transitions in self-assembled InAs quantum dots w... more We investigate the far infrared magneto-optical transitions in self-assembled InAs quantum dots with different lateral diameters and we show that a purely electronic model is unable to account for the experimental data. We calculate the coupling between the mixed electron-LO-phonon states using the Fröhlich Hamiltonian, from which we determine the polaron states as well as the energies of the dipolar
35th International Conference on Infrared, Millimeter, and Terahertz Waves, 2010
A THz quantum cascade structure has been designed to allow population relaxation between crossing... more A THz quantum cascade structure has been designed to allow population relaxation between crossing Landau levels from different subbands under perpendicular magnetic field. Electroluminescence measurements show intersubband luminescence as well as inter-Landau level emission (cyclotron emission).
Low-temperature infrared magnetoabsorption experiments were carried out on Hgl kMn~Te mixed cryst... more Low-temperature infrared magnetoabsorption experiments were carried out on Hgl kMn~Te mixed crystals with compositions corresponding to the semiconducting (positive energy gap) range. Measurements were performed in the spectral region 100-350 meV in Voigt and Faraday geometries, using both linear and circular polarizations. The magneto-optical data provide observation of interband I 8~I 6 transitions. In addition, transitions from acceptor levels to I 6 Landau levels were observed. The interband magneto-optical transitions are interpreted within the framework of the Pidgeon-Brown model, modified by the contributions of the s-d and p-d spin-spin exchange interaction between band electrons and localized Mn~+ spins. From the theoretical fits of the transition energies to the observed absorption lines, the relative magnetization A (H, T) is deduced at T = 4.2 and 2 K for alloys of various Mn content. In contrast with zero-gap Hgl kMnk Te, in the present case 3 (H, T) exhibits a nearly linear magnetic field dependence and depends only weakly on temperature. These features are related to the strong antiferromagnetic interactions between the localized magnetic moments, Conduction electrons in crystals in this composition range exhibit large and positive g factors as a consequence of the s-d exchange coupling.
When a Dirac fermion system acquires an energy-gap, it is said to have either trivial (positive e... more When a Dirac fermion system acquires an energy-gap, it is said to have either trivial (positive energy-gap) or non-trivial (negative energy-gap) topology, depending on the parity ordering of its conduction and valence bands. The non-trivial regime is identified by the presence of topological surface or edge-states dispersing in the energy gap of the bulk and is attributed a non-zero topological index. In this work, we show that such topological indices can be determined experimentally via an accurate measurement of the effective velocity of bulk massive Dirac fermions. We demonstrate this approach analytically starting from the Bernevig-Hughes-Zhang Hamiltonian to show how the topological index depends on this velocity. We then experimentally extract the topological index in Pb 1-x Sn x Se and Pb 1-x Sn x Te using infrared magnetooptical Landau level spectroscopy. This approach is argued to be universal to all material classes that can be described by a Bernevig-Hughes-Zhang-like model and that host a topological phase transition.
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface state... more Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead-tin salts Pb 1−x Sn x Se and Pb 1−x Sn x Te. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb 1−x Sn x Se and Pb 1−x Sn x Te ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb 1−x Sn x Se and Pb 1−x Sn x Te for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the topological phase transition in TCI. We will finally present our views on prospects and open questions that have yet to be addressed in magneto-optical spectroscopy studies on Pb 1-x Sn x Se and Pb 1−x Sn x Te.
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