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| 2. |
- Harati Zadeh, Hamid, 1964-, et al.
(författare)
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Photoluminescence study of Si-doped GaN/Al0.07Ga0.93N multiple quantum wells with different dopant position
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:25, s. 5071-5073
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Tidskriftsartikel (refereegranskat)abstract
- The Si-doped GaN/Al0.07Ga0.93N multiple quantum wells (MQW) were investigated, using photoluminescence (PL) and time-resolved (PL) measurements. The influence of Si doping on the emission energy and recombination dynamics of the MWQs were also investigated, with different dopant position in the wells. It was observed that the redshifted emission of the MQWs was attributed to the self-energy shift of the electron states due to the correlated motion of the electrons exposed to the fluctuating potential of the donor ions. It was also observed that the PL decay time of the sample was ∼760 ps, at low temperature.
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| 3. |
- Wongmanerod, S, et al.
(författare)
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Many-body effects in highly p-type modulation-doped GaAs/AlxGa1-xAs quantum wells
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:4, s. 2794-2798
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Tidskriftsartikel (refereegranskat)abstract
- Many-body effects have been optically investigated for modulation-doped quantum wells at high acceptor densities. The observed band-gap shrinkage, up to approximate to 20 meV, is consistent with calculations based on the Hartree and random-phase approximations including the finite well width effect. A recombination near the Fermi edge with light-hole character is strikingly enhanced at high acceptor densities. An interpretation based on carrier-carrier interaction is proposed. Finally, the exciton is found to be quenched for hole densities higher than approximate to 2x10(12) cm(-2).
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| 4. |
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| 5. |
- Araujo, C. M., et al.
(författare)
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Electrical resistivity, MNM transition and band-gap narrowing of cubic GaN : Si
- 2002
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Ingår i: Microelectronics Journal. - 0026-2692. ; 33:4, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistivity of the Si-donor cubic GaN is investigated theoretically at low temperature. The critical impurity concentration, N-c, for the metal-nonmetal transition is estimated in three different ways: from using the generalized Drude approach (GDA) for the resistivity; from the vanishing of the chemical potential calculated using the dielectric function model with a Lorentz-Lorenz correction; from finding the crossing point between the energy in the insulating and metallic states. The bandgap narrowing (BGN) has been determined theoretically and experimentally above the MNM transition, The experimental data have been obtained with photoluminescence measurements. Theoretical and experimental results are in rough agreement in the range of impurity concentration of interest.
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| 6. |
- Boström, Mathias, et al.
(författare)
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Comment on "Calculation of the Casimir force between imperfectly conducting plates"
- 2000
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 61:4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In a recent paper [Phys. Rev. A 59, R3149 (1999)] Lamoreaux reported calculations of the Casimir force. The experimentally found permittivity was used in the calculations. Large deviations were found between numerically evaluated forces and forces derived from a series expanded plasma model. We would like to comment on a few results presented in this work. First, we claim that important features of the imaginary component of the permittivity of copper, presented in Fig. 1(a) are due to the interpolation procedure and are not caused by physical phenomena. These features influence the calculated permittivity for imaginary frequencies, which is the quantity used to calculate the Casimir attraction. Second, we discuss the extrapolation procedure used for low frequencies. The results depend substantially on how this extrapolation is performed.
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| 7. |
- Boström, Mathias, et al.
(författare)
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Entropy of the Casimir effect between real metal plates
- 2004
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 339:01-Feb, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- We first derive the zero-and-finite-temperature dispersion-forces in terms of changes in the energy of the electromagnetic normal modes of the system. We then use this to evaluate the entropy of the electromagnetic normal modes for the "Casimir system" consisting of two metal plates. We demonstrate that this entropy obeys the Nernst heat theorem. (C) 2004 Elsevier B.V. All rights reserved.
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| 8. |
- Boström, Mathias, et al.
(författare)
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Fractional van der Waals interaction between thin metallic films
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:3, s. 2204-2210
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Tidskriftsartikel (refereegranskat)abstract
- The van der Waals (vdW) interaction between thin metallic films varies with separation as the separation to a fractional power. This is in contrast to the usual integer-power separation dependence between objects such as atoms, dielectric films, or thick metallic films. We have calculated the free energy of attraction between sheets of gold, silver, copper, beryllium, and tungsten numerically using experimentally found dielectric functions. The results are compared with the corresponding analytical results obtained using simple model dielectric functions. We have investigated how thin the metallic films must be in order for the fractional vdW interaction to be present. To our knowledge, fractional vdW interaction has not yet been confirmed experimentally.
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| 9. |
- Boström, Mathias, et al.
(författare)
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Retardation-enhanced van der Waals force between thin metal films
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:11, s. 7523-7526
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Tidskriftsartikel (refereegranskat)abstract
- We recently investigated the van der Waals force between thin metal films. Under certain conditions this force decrease with separation to a fractional power. In the present work we use optical data of metals and the zero-temperature Lifshitz formalism to demonstrate a retardation effect. The retarded attraction between thin metal films may be larger than the nonretarded attraction. This property is related to a comparatively weak retardation dependence of the energy that originates from the transverse magnetic modes. At separations where the transverse electric modes give a significant contribution, the net effect can actually be an increased attraction. This effect vanishes with increasing film thickness and with increasing dissipation.
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| 10. |
- Boström, Mathias, et al.
(författare)
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Temperature effects on the Casimir attraction between a pair of quantum wells
- 2000
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Ingår i: Microelectronic Engineering. - 0167-9317 .- 1873-5568. ; 51, s. 287-297
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Tidskriftsartikel (refereegranskat)abstract
- We present calculations of the free energy of attraction between two quantum wells in which the wells are treated as strictly two-dimensional metallic sheets. The van der Waals force exhibits fractional separation dependence in this system. This is in contrast to the usual integer separation dependence. We have performed numerical calculations at different temperatures and with different carrier densities. Except at very low temperatures thermal effects will be a dominating source of attraction. We have determined temperature criteria that must be fulfilled for the fractional separation dependence to be observable. Thermal corrections will be important already at temperatures less than 1 K. We further make some comments on a recent measurement of the Casimir force.
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