| 1. |
- Rouhani-Kalleh, A., et al.
(författare)
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Resistance in sub-m size GaAs lines
- 1987
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 3:4, s. 417-419
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistance in GaAs submicron mesa lines has been studied as a function of the line width. Using molecular beam epitaxy two types of conducting layers were made: an n+-layer and a two-dimensional electron gas confined to an (AlGa)As/GaAs heterostructure. Processing of the lines was made by photolithography, electron beam lithography and ion etching. Resistance data at 77 K and 300 K are discussed for line widths in the interval 0.2 to 5 m. A size dependent conduction was found and interpreted in terms of geometry induced limitation of the effective conducting path
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| 2. |
- MOLENKAMP, LW, et al.
(författare)
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STOCHASTIC COULOMB-BLOCKADE AND SCALING OF CHARGING ENERGY IN A DOUBLE-QUANTUM DOT SYSTEM
- 1994
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Ingår i: Superlattices and Microstructures. - : ACADEMIC PRESS (LONDON) LTD. - 0749-6036 .- 1096-3677. ; 16:3, s. 275-278
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the transport properties of a device consisting of two quantum dots, defined electrostatically in a (Al,Ga)As heterostructure. In the series conductance of the two dots, we observe irregularly spaced conductance peaks of fluctuating amplitude. This behaviour results from transport in the stochastic Coulomb blockade regime. In a second experiment, we measure the charging energy of one dot through the effect of its potential (which varies in a saw-tooth fashion with gate voltage) on the conductance of the other dot. We find that the charging energy scales quadratically with the reflection probability of the tunnel barriers, in agreement with a recent theory.
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| 3. |
- Akabli, H., et al.
(författare)
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Intersubband energies in Al1-yInyN/Ga1-xInxN heterostructures with lattice constant close to aGaN
- 2012
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 52:1, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the conduction band profile and the intersubband transition energy, E-12, of Al1-yInyN/Ga1-xInxN quantum well structures. We have considered how material parameters such as non-parabolicity and the uncertainty in the bowing parameter affect E-12 and the corresponding wavelength, lambda(12). The calculations include strain and cover the transition range from telecommunication wavelengths (1.55 mu m) to the mid-infrared (similar to 10 mu m). Our results show that the transition energies of strain-free Al1-yInyN/Ga1-xInxN quantum well structures, which are lattice-matched to GaN (y = 17.7%, x = 0), resulted in wavelengths above similar to 2 mu m. To reach shorter wavelengths, we explored structures with other indium concentrations but maintaining a small mismatch to GaN. For similar to 1% lattice mismatch the wavelength lambda(12) could be reduced to less than 1.55 mu m. The results serve as a starting point for designing and epitaxial growth of photonic intersubband structures.
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| 4. |
- Arnaudov, B., et al.
(författare)
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Free-to-bound radiative recombination in highly conducting InN epitaxial layers
- 2004
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 36:4-6, s. 563-571
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical simulation of near-band-edge emission spectra of highly conducting n-InN assuming the model of 'free-to-bound' radiative recombination (FBRR) of degenerate electrons from the conduction band with nonequilibrium holes located in the valence band tails. We also study experimental photoluminescence (PL) spectra of highly conducting InN epitaxial layers grown by MBE and MOVPE with electron concentrations in the range (7.7 × 1017-6 × 1018) cm-3 and find that the energy positions and shape of the spectra depend on the impurity concentration. By modeling the experimental PL spectra of the InN layers we show that spectra can be nicely interpreted in the framework of the FBRR model with specific peculiarities for different doping levels. Analyzing simultaneously the shape and energy position of the InN emission spectra we determine the fundamental bandgap energy of InN to vary between Eg = 692 meV for effective mass mn0 = 0.042m0 and Eg =710 meV for mn0 = 0.1m0. © 2004 Elsevier Ltd. All rights reserved.
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| 5. |
- Badel, Xavier, et al.
(författare)
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Formation of ordered pore arrays at the nanoscale by electrochemical etching of n-type silicon
- 2004
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 36:1/3, s. 245-254
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical etching has been studied to structure n-type silicon substrates at the nanoscale. In this work, well-ordered pore arrays with diameters in the range of 150-500 nm and depths up to 50 mum have been fabricated. The pores were successfully formed by anodic etching in (100)oriented n-type silicon wafers of low-resistivity, typically 1 Omegacm, using aqueous hydrofluoric acid solutions. The lithographic step was performed in a thermally grown oxide using a stepper and dry oxide etching technique. Two types of oxide openings and pitch sizes were tested. The smallest oxide opening realised at this stage was 0.5 mum for a pitch of 1 mum. Stable pore formation was obtained and the smallest pore size obtained was about 200 nm with an aspect ratio close to 100.
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| 6. |
- Behloul, M., et al.
(författare)
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Theoretical investigation of the electronic and magnetic properties of Zn (Fe, Co) Se : Ab initio calculations and Monte Carlo simulations
- 2019
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Ingår i: Superlattices and Microstructures. - : ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD. - 0749-6036 .- 1096-3677. ; 127, s. 66-70
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Tidskriftsartikel (refereegranskat)abstract
- On the basis of spin density functional calculation, the electronic and magnetic properties of ZnSe doped with double impurities Zn1-2xFexCoxSe (x = 0.05) are studied using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method within the local density approximation (LDA). The half-metallic ferromagnetic nature of (Fe, Co) doped ZnSe is investigated. Therefore the electronic structure and magnetic properties of Zn1-2xFexCoxSe exhibit a half-metallic ferromagnetic character; the stability of ferromagnetic (FM) compared to the disorder local moment (DLM) has been discussed. Our calculation is supported by Monte Carlo simulations (MCS) based on the heat bath algorithm. We have examined the effects of system size L on magnetization, specific heat and magnetic susceptibility. The spin density functional calculation results are in good agreement with the literature, especially for 5% of (Co, Fe) each, which gives the most interesting results.
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| 7. |
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| 8. |
- Benhouria, Y., et al.
(författare)
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Thermodynamic properties and hysteresis behaviors of a mixed spin-3/2 and spin-1/2 Ising double walled ferrielectric nanotubes : A Monte Carlo study
- 2014
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 75, s. 761-774
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Tidskriftsartikel (refereegranskat)abstract
- The hysteresis loops and the thermodynamic properties of a ferroelectric or ferrielectric double walled nanotubes (A and B) are studied within the Ising model with mixed spins (S-A = 3/2 and S-B = 1/2) in the presence of the crystal and the external longitudinal electric fields. We use the Monte Carlo method to investigate the effects of the external electric field, the crystal field and the exchange interactions on the total polarization, susceptibility, specific heat and the internal energy of a double walled nanotubes (DWNTs).
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| 9. |
- Berland, Kristian, 1983
(författare)
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A general solution to the Schrodinger-Poisson equation for a charged hard wall: Application to potential profile of an AlN/GaN barrier structure
- 2011
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 50:4, s. 411-418
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Tidskriftsartikel (refereegranskat)abstract
- A general, system-independent, formulation of the parabolic Schrodinger-Poisson equation is presented for a charged hard wall in the limit of complete screening by the ground state. It is solved numerically using iteration and asymptotic boundary conditions. The solution gives a simple relation between the band bending and sheet charge density at an interface. Approximative analytical expressions for the potential profile and wave function are developed based on properties of the exact solution. Specific tests of the validity of the assumptions leading to the general solution are made. The assumption of complete screening by the ground state is found be a limitation; however, the general solution provides a fair approximate account of the potential profile when the bulk is doped. The general solution is further used in a simple model for the potential profile of an AlN/GaN barrier structure. The result compares well with the solution of the full Schrodinger-Poisson equation.
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| 10. |
- Berman, G. P., et al.
(författare)
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Single-spin measurements for quantum computation using magnetic resonance force microscopy
- 2003
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 34:06-mar, s. 509-511
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Tidskriftsartikel (refereegranskat)abstract
- The quantum theory of a single-spin measurement using magnetic resonance force microscopy is presented. We use an oscillating cantilever-driven adiabatic reversal technique. The frequency shift of the cantilever vibrations is estimated. We show that the frequency shift causes the formation of a Schrodinger cat state for the cantilever. The interaction between the cantilever and the environment quickly destroys the coherence between the two cantilever trajectories. It is shown that using partial adiabatic reversals one can obtain a significant increase in the frequency shift. We discuss the possibility of sub-magneton spin density detection in molecules using magnetic resonance force microscopy.
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