| 1. |
- Bobbert, PA, et al.
(författare)
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Exchange-correlation energy of a hole gas including valence band coupling
- 1997
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 56:7, s. 3664-3671
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated an accurate exchange-correlation energy of a hole gas, including the complexities related to the valence band coupling as occurring in semiconductors like GaAs, but excluding the band warping. A parametrization for the dependence on the density and the ratio between light-and heavy-hole masses is given. We apply our results to a hole gas in an AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well and calculate the two-dimensional band structure and the band-gap renormalization. The inclusion of the valence band coupling in the calculation of the exchange-correlation potentials for holes and electrons leads to a much better agreement between theoretical and experimental data than when it is omitted.
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| 2. |
- Croitoru, MD, et al.
(författare)
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Electroluminescence spectra of an STM-tip-induced quantum dot
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 68:19
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the electroluminescence spectrum of an STM-tip-induced quantum dot in a GaAs surface layer. A flexible model has been developed that combines analytical and numerical methods and describes the key features of many-particle states in the STM-tip-induced quantum dot. The dot is characterized by its depth and lateral width, which are experimentally controlled by the bias and current. We find, in agreement with experiment, that increasing the voltage on the STM tip results in a redshift of the electroluminescence peaks, while the peak positions as a function of electron tunneling current through the STM tip reveal a blueshift.
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| 3. |
- Croitoru, MD, et al.
(författare)
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Electroluminescence spectra of an STM-tip-induced quantum dot
- 2004
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 21:2-4, s. 270-274
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the electroluminescence spectrum of an STM-tip-induced quantum dot in a GaAs surface layer. A flexible model has been developed, that combines analytical and numerical methods and describes the key features of many-particle states in the STM-tip-induced quantum dot. The dot is characterized by its depth and lateral width, which are experimentally controlled by the bias and the tunneling current. We find, in agreement with experiment, that increasing voltage on the STM-tip results in a red shift of the electroluminescence peaks, while the peak positions as a function of the electron tunneling current through the STM-tip reveal a blue shift. (C) 2003 Elsevier B.V. All rights reserved.
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| 4. |
- Croitoru, MD, et al.
(författare)
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Influence of the characteristics of the STM-tip on the electroluminescence spectra
- 2005
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Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 27:1-2, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- We analyze the influence of the characteristics of the STM-tip (applied voltage, tip radius) on the electroluminescence spectra from an STM-tip-induced quantum dot. We find that positions of electroluminescence peaks, attributed to the electron-hole recombination in the quantum dot, are very sensitive to the characteristics of the tip, namely increasing voltage on the STM-tip results in a red shift of the electroluminescence peaks, while the peak positions as a function of the tip radius reveal a non-monotonous behavior. (c) 2004 Elsevier B.V. All rights reserved.
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| 5. |
- Haverkort, JEM, et al.
(författare)
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Design of a polarization independent SOA at 1.55 mu m using composite InAsP/InGaAs quantum wells.
- 1999
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Ingår i: ECIO99: 9TH EUROPEAN CONFERENCE ON INTEGRATED OPTICS AND TECHNICAL EXHIBITION. - : IST INT COMUNICAZIONI. ; , s. 483-486
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Konferensbidrag (refereegranskat)abstract
- We aim to extend the polarization independent SOA reported by Tiemeijer(1) to 1550 nm. Conventional quantum wells (QW) do not allow TM-gain at 1550 nm without exceeding the critical layer thickness. Composite InAsP/InGaAs QWs show high TM-differential gain at 1550 nm while simultaneously providing strain compensation.
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| 6. |
- Haverkort, JEM, et al.
(författare)
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Design of composite InAsP/InGaAs quantum wells for a 1.55 mu m polarization independent semiconductor optical amplifier
- 1999
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 75:18, s. 2782-2784
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a composite InAsP/InGaAs quantum well in which an 8 nm tensile strained InGaAs well is surrounded by two compressively strained InAsP layers which feature a 70:30 conduction band offset ratio. The composite quantum well is found to provide a high TM differential gain. The InAsP layers provide strain compensation while simultaneously shifting the band gap to the relevant 1.55 mu m wavelength region and increasing the electron confinement. Composite InAsP/InGaAs quantum wells are a promising candidate for realizing a polarization independent semiconductor optical amplifier at 1.55 mu m. (C) 1999 American Institute of Physics. [S0003-6951(99)01944-0].
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| 7. |
- Jacobs, SEJ, et al.
(författare)
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Spatially resolved scanning tunneling luminescence on self-assembled InGaAs/GaAs quantum dots
- 2003
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 83:2, s. 290-292
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Tidskriftsartikel (refereegranskat)abstract
- Scanning-tunneling microscope induced luminescence at low temperature has been used to study the carrier injection into single self-assembled InGaAs/GaAs quantum dots. Electrons are injected from the tip into the dots, which are located in the intrinsic region of a p-i-n junction, and contain excess holes under typical operational conditions. Only a fraction (similar to4%) of the dots is found to be optically active under local electrical excitation. Spatial dependent measurements indicate a highly nonhomogeneous electron diffusion towards the dots. By analyzing the spatial dependence of individual peaks in the measured spectra, the contributions of individual dots to the total, multidot spectrum can be disentangled. (C) 2003 American Institute of Physics.
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| 8. |
- Kemerink, Martijn, et al.
(författare)
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Effect of strain on a second-order van Hove singularity in AlxGa1-xAs/InyGa1-yAs quantum wells
- 1996
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 54:15, s. 10644-10651
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Tidskriftsartikel (refereegranskat)abstract
- We have performed low-temperature photoluminescence and photoluminescence excitation (PLE) measurements on highly degenerate p-type GaAs and InyGa1-yAs quantum wells. In the PLE spectrum of the GaAs well, evidence of a second-order van Hove singularity in the joint density of states of the ground-state light-hole and electron bands is found. This singularity results from the equality of ground-state light-hole and electron effective masses near the Gamma point, being a much more restrictive demand than the usual condition for a van Hove singularity, which requires only the equality of first derivatives of the subband dispersions. The second-order van Hove singularity gives rise to a power-law divergence at the singular point, whereas the corresponding usual van Hove singularity results in a steplike discontinuity in the joint density of states. The observed singularity could be described extremely well by a simple analytical model. The increased energy gap between light- and heavy-hole ground states in the compressively strained InyGa1-yAs well enhances the valence-band parabolicity, resulting in the disappearance of the van Hove singularity. Furthermore, it is shown that the anisotropic character of the heavy-hole ground state in GaAs is strongly suppressed in the InyGa1-yAs system. All experiments are in good agreement with our numerical modeling, based on an exact solution of the 4 x 4 Luttinger Hamiltonian.
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| 9. |
- Kemerink, Martijn, et al.
(författare)
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Enhancement of spin-dependent hole delocalization in degenerate asymmetric double quantum wells
- 1996
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 53:15, s. 10000-10007
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Tidskriftsartikel (refereegranskat)abstract
- Exact, self-consistently calculated eigenfunctions and eigenvalues of the valence band in degenerate asymmetric double quantum wells are obtained from the full 4x4 Luttinger Hamiltonian for different hole densities. We found the solutions to be extremely sensitive to the charge density. The charge induces an extra asymmetry in the confining potential and leads to a smaller separation of the hole levels in the adjacent wells. This strongly enhances the different leakage of wave functions with opposite magnetic moment, called spin-dependent hole delocalization (SDHD). Furthermore, it is shown that the SDHD of the heavy-holt: states can be enhanced by increasing the confinement of the Light-hole states through adjustment of the height of the confining barriers. The theoretical results are shown to be in excellent agreement with transport and optical experiments, which are proven to be largely determined by space-charge effects.
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| 10. |
- Kemerink, Martijn, et al.
(författare)
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Exchange interaction in degenerate p-type quantum wells
- 1998
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Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 256, s. 503-506
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Tidskriftsartikel (refereegranskat)abstract
- A detailed comparison between a magneto-transport experiment on a p-type GaAs/AlGaAs quantum well and model calculations is presented. It is shown that for all magnetic fields the Shubnikov-de Haas (SdH) trace is strongly influenced by the exchange interaction, in contrast with n-type structures where this interaction is only important in high magnetic fields. As a consequence, the effective hole masses that are extracted from the temperature dependence of the SdH oscillations are not a good measure of the single-particle hole mass, and can be regarded as meaningless. (C) 1998 Elsevier Science B.V. All rights reserved.
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