Quantum confinement in Si and Ge nanostructures
E. G. Barbagiovanni, D. J. Lockwood, P. J. Simpson, and L. V. Goncharova
We apply perturbative effective mass theory as a broadly applicable theoretical model for quantum confinement (QC) in all Si and Ge nanostructures including quantum wells (QWs), wires (Q-wires), and dots (QDs). Within the limits of strong, medium, and weak QC, valence and conduction band edge energy ... [J. Appl. Phys. 111, 034307 (2012)] published Wed Feb 8, 2012.
Highly tunable whispering gallery mode semiconductor lasers with controlled absorber
A. N. Baranov, G. Boissier, R. Teissier, A. M. Monakhov, V. V. Sherstnev et al.
Tunable semiconductor lasers with controlled absorber based on GaInAsSb/GaAlAsSb quantum well heterostructure was fabricated and experimentally studied. The emission wavelength of these lasers shifts from 2.24 to 2.28 [mu]m when the bias on the control contact decreases from the voltage equal to tha ... [Appl. Phys. Lett. 100, 061112 (2012)] published Tue Feb 7, 2012.
Sub-250 nm room-temperature optical gain from AlGaN/AlN multiple quantum wells with strong band-structure potential fluctuations
Emanuele Francesco Pecora, Wei Zhang, A. Yu. Nikiforov, Lin Zhou, David J. Smith et al.
Deep-UV optical gain has been demonstrated in AlGaN/AlN multiple quantum wells under femtosecond optical pumping. Samples were grown by molecular beam epitaxy under a growth mode that introduces band structure potential fluctuations and high-density nanocluster-like features within the AlGaN wells. ... [Appl. Phys. Lett. 100, 061111 (2012)] published Tue Feb 7, 2012.
Giant negative magnetoresistance in high-mobility two-dimensional electron systems
A. T. Hatke, M. A. Zudov, J. L. Reno, L. N. Pfeiffer, and K. W. West
We report on a giant negative magnetoresistance in very high mobility GaAs/AlGaAs heterostructures and quantum wells. The effect is the strongest at B~=1 kG, where the magnetoresistivity develops a minimum emerging at T<~2 K. Unlike the zero-field resistivity which saturates at T~=2 K, the resistivi ... [Phys. Rev. B 85, 081304 ] published .
Ionization of coherent excitons by strong terahertz fields
B. Ewers, N. S. Koster, R. Woscholski, M. Koch, S. Chatterjee et al.
The interaction of coherent excitons with intense, single-cycle terahertz (THz) pulses is investigated. A significant bleaching of the 1s-exciton resonance develops into a splitting of the absorption peak and the emergence of pronounced wings with increasing THz field strength. A quantum-mechanical ... [Phys. Rev. B 85, 075307 ] published .
Nonadiabatic switching of a photonic band structure: Ultrastrong light-matter coupling and slow-down of light
M. Porer, J.-M. Menard, A. Leitenstorfer, R. Huber, R. Degl'Innocenti et al.
We map out the band structure of a one-dimensional photonic crystal while a 12-fs control pulse activates ultrastrong interaction with quantized electronic transitions in semiconductor quantum wells. Phase-locked multi-terahertz transients trace the buildup of a large vacuum Rabi splitting and an un ... [Phys. Rev. B 85, 081302 ] published .
Deep traps and enhanced photoluminescence efficiency in nonpolar a-GaN/InGaN quantum well structures
A. Y. Polyakov, Lee-Woon Jang, Dong-Seob Jo, In-Hwan Lee, N. B. Smirnov et al.
Nonpolar (11-20) a-GaN/InGaN quantum well (QW) structures were grown by metalorganic chemical vapor deposition on r-plane (1-102) sapphire substrate using a two-stage growth procedure. Our studies demonstrate that, in contrast to polar QWs, these structures show the presence of deep electron traps w ... [J. Appl. Phys. 111, 033103 (2012)] published Fri Feb 3, 2012.
Temperature dependence of the intraexcitonic AC Stark effect in semiconductor quantum wells
M. Wagner, M. Teich, M. Helm, and D. Stehr
We have investigated the temperature-dependent, intraexcitonic AC Stark effect that manifests itself in a line splitting of the heavy-hole 1s exciton transition in a GaAs/AlGaAs multi quantum well when the 1s-2p intraexciton transition is driven by intense THz light. The observed wavelength-dependen ... [Appl. Phys. Lett. 100, 051109 (2012)] published Thu Feb 2, 2012.
Surface depletion mediated control of inter-sub-band absorption in GaAs/AlAs semiconductor quantum well systems
Walter R. Buchwald, Justin W. Cleary, and Joshua Hendrickson
The modification of quantum well inter-sub-band absorption properties due to surface depletion induced band bending is reported. Fourier transform infrared spectroscopy measurements of a GaAs/AlAs multiple quantum well system reveal a reduction in the characteristic absorption resonance in correlati ... [Appl. Phys. Lett. 100, 051110 (2012)] published Thu Feb 2, 2012.
Molecular beam epitaxy growth of AlGaN quantum wells on 6H-SiC substrates with high internal quantum efficiency
Wei Zhang, A. Yu. Nikiforov, C. Thomidis, J. Woodward, H. Sun et al.
The authors report the development of high internal quantum efficiency AlN/AlGaN/AlN double heterostructures and AlGaN/AlN multiple quantum wells (MQWs) grown on 6H-SiC and 4H-SiC substrates of various miscuts by plasma-assisted molecular-beam epitaxy. The authors find that the luminescence spectra ... [J. Vac. Sci. Technol. B 30, 02B119 (2012)] published Wed Feb 1, 2012.
Molecular beam epitaxial growth and characterization of nitrogen delta-doped AlGaAs/GaAs quantum wells
Shin-ichiro Furuse, Kengo Sumiya, Masato Morifuji, and Fumitaro Ishikawa
The authors carry out delta-doping at the middle of AlGaAs/GaAs quantum wells employing molecular beam epitaxy and varying the nitrogen coverage up to 0.5 monolayers. Transmission electron micrography and x ray diffraction indicate the introduction of a nitrogen delta-doped layer with precisely cont ... [J. Vac. Sci. Technol. B 30, 02B117 (2012)] published Wed Feb 1, 2012.
Blueshift in sulfur treated GaAsP/AlGaAs near surface quantum well
Suparna Pal, S. D. Singh, S. Porwal, S. W. D'Souza, S. R. Barman et al.
Large blueshift was observed in a near-surface GaAsP/AlGaAs quantum well upon treatment with NaSxHO solution. Very slow etching with simultaneous surface passivation of the quantum well was obtained using this chemical treatment. Photoreflectance (PR) spectra exhibit maximum blueshift of 28 meV afte ... [J. Vac. Sci. Technol. A 30, 021401 (2012)] published Wed Feb 1, 2012.
Quantitative modeling of spin relaxation in quantum dots
J. P. Hansen, S. A. Sorngard, M. Forre, and E. Rasanen
We use numerically exact diagonalization to calculate the spin-orbit- and phonon-induced triplet-singlet relaxation rate in a two-electron quantum dot exposed to a tilted magnetic field. Our scheme includes a three-dimensional description of the quantum dot, the Rashba and the linear and cubic Dress ... [Phys. Rev. B 85, 035326 ] published .
High-frequency electrical charge and spin control in a single InGaAs quantum dot
J. Nannen, W. Quitsch, S. Eliasson, T. Kummell, and G. Bacher
We report on the charging behavior of a single self-assembled InGaAs quantum dot with unpolarized and spin-polarized electrons under direct current (DC) and high-frequency biasing. The tunnel coupling of the quantum dot to a spin-polarized electron reservoir leads to characteristic voltage dependenc ... [Phys. Rev. B 85, 035325 ] published .
Cyclotron resonance and intersubband transitions in symmetric InSb/AlInSb quantum wells with a perpendicular magnetic field
X. G. Wu and X. H. Zhang
Electronic states in symmetric InSb/AlInSb quantum wells are studied theoretically. An eight-band kp calculation is performed for quantum wells with different barrier heights and well widths in the presence of a magnetic field applied perpendicularly to the quantum well. Influences due to strain and ... [J. Appl. Phys. 111, 023716 (2012)] published Tue Jan 31, 2012.
Reordering orbitals of semiconductor multi-shell quantum dot-quantum well heteronanocrystals
Mehmet Şahin, Sedat Nizamoglu, Ozan Yerli, and Hilmi Volkan Demir
Based on self-consistent computational modeling of quantum dot-quantum well (QDQW) heteronanocrystals, we propose and demonstrate that conduction-electron and valence-hole orbitals can be reordered by controlling shell thicknesses, unlike widely known core/shell quantum dots (QDs). Multi-shell nanoc ... [J. Appl. Phys. 111, 023713 (2012)] published Fri Jan 27, 2012.
Effect of an electron blocking layer on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes
Dong-Yul Lee, Sang-Heon Han, Dong-Ju Lee, Jeong Wook Lee, Dong-Joon Kim et al.
We report the effect of an electron blocking layer (EBL) on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes (LEDs). Electric-field-dependent ER measurements showed an enhanced piezoelectric field in LEDs with a p-AlGaN EBL compared with LEDs without EBL. In contrast, ... [Appl. Phys. Lett. 100, 041119 (2012)] published Fri Jan 27, 2012.
Photoreflectance study of direct-gap interband transitions in Ge/SiGe multiple quantum wells with Ge-rich barriers
H. P. Hsu, P. H. Wu, Y. S. Huang, D. Chrastina, G. Isella et al.
Photoreflectance (PR) was used to study the direct-gap interband transitions in strain-compensated Ge/SiGe multiple quantum well (MQW) structures with Ge-rich SiGe barriers grown by low-energy plasma-enhanced chemical vapor deposition. The PR spectra revealed a wide range of possible optical transit ... [Appl. Phys. Lett. 100, 041905 (2012)] published Thu Jan 26, 2012.
Quantized nu=5/2 State in a Two-Subband Quantum Hall System
J. Nuebler, B. Friess, V. Umansky, B. Rosenow, M. Heiblum et al.
The evolution of the fractional quantum Hall state at filling 5/2 is studied in density tunable two-dimensional electron systems formed in wide wells in which it is possible to induce a transition from single- to two-subband occupancy. In 80 and 60 nm wells, the quantum Hall state at 5/2 filling of ... [Phys. Rev. Lett. 108, 046804 ] published .
Quantum state transfer between hybrid qubits in a circuit QED
Zhi-Bo Feng
In this Brief Report, we propose a theoretical scheme to transfer quantum states between superconducting charge qubits and semiconductor spin qubits in a circuit QED device. Under dispersive conditions, resonator-assisted state transfer between qubits can be performed controllably only by addressing ... [Phys. Rev. A 85, 014302 ] published .
Pressure-dependent reordering of valence band states in GaN/AlGaN quantum wells
W. Bardyszewski and S. P. Lepkowski
We show theoretically that for narrow GaN/AlGaN quantum wells, lattice matched to GaN substrate and grown along the c-crystallographic direction a pressure-dependent reordering of the topmost valence subbands having different symmetries occurs. This reordering depends critically on the values of the ... [Phys. Rev. B 85, 035318 ] published .