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- Engström, Olof, 1943, et al.
(författare)
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Properties of Metal/High-k Oxide/Graphene Structures
- 2017
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 80:1, s. 157-176
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Konferensbidrag (refereegranskat)abstract
- The challenge of interpreting experimental data from capacitance versus voltage (C-V) measurements on metal/high-k oxide/graphene (MOG) structures is discussed. Theoretical expressions for the influence of interface states, bulk oxide traps, measurement frequency, temperature and puddles are derived and compared with experiments. The nature of oxide traps and their impact on C-V data is treated especially from the view of electron-lattice interaction at electron emission and capture and possible performance as border traps, resembling interface states. We find that characterization on detailed physical origins leading to effects on C-V data is a more complicated issue than the corresponding analysis of metal/oxide/semiconductor (MOS) structures.
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| 2. |
- Engström, Olof, 1943
(författare)
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Compensation effects at electron traps in semiconductors
- 2013
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Ingår i: Monatshefte für Chemie. - : Springer Science and Business Media LLC. - 0026-9247 .- 1434-4475. ; 144:1, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- The basic qualities for fulfilling the Meyer-Neldel rule (MNR) for thermal electron emission from semiconductor traps are investigated. A trap model including vibronic properties is used with varying entropy arising from the change in elasticity of the ionic part of the trap potential when an electron transition takes place. This gives rise to a system where the compensation effect originates from the increasing entropy change as a function of the enthalpy supply needed for the transition process in concord with Yelon-Movaghar theory. The entropy increase connects to a decrease in the activation energy for electron capture, which amplifies the compensation effect for MNR manifestation. By comparing with experimental data, the result achieved from the model clarifies the experimental observation of class partitioning for centers in GaAs, obeying the MNR. Furthermore, it is demonstrated that traps at metal-oxide-silicon interfaces, with the same properties as bulk traps following the MNR, give rise to capture cross-sections steeply increasing with the Gibbs free energy involved in carrier emission, as found by experiment.
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| 5. |
- Engström, Olof, 1943, et al.
(författare)
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Electron capture at InAs/GaAs quantum dots
- 2004
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Ingår i: 8th International Conference on Nanometer Scale Science and Technology, Venice, Italy, 2004.
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Konferensbidrag (refereegranskat)
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| 6. |
- Engström, Olof, 1943, et al.
(författare)
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Electron capture cross sections of InAs/GaAs quantum dots
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85:14, s. 2908-2910
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Tidskriftsartikel (refereegranskat)abstract
- The thermal emission rates of electrons from InAs/GaAs quantum dots were measured, to found the capture cross sections in the extremely high region of 10-11-10-10 cm2. An additional method based on a static measurement at thermal equilibrium was used where the Fermi level was positioned at the free energy level of the quantum dot s shell. A Schottky diode with a plane of QDs grown in its depletion region and back-biased in such a way that the Fermi level coincides with the electron energy level. The Fermi level passes the lowest energy level of the QD, at the voltage marked by Vp in the graphs.
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| 9. |
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| 10. |
- Fu, Ying, 1964, et al.
(författare)
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Emission rates for electron tunneling from InAs quantum dots to GaAs substrate
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:11, s. 6477-6481
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Tidskriftsartikel (refereegranskat)abstract
- Tunneling emission rates of electrons from InAs quantum dots (QD) in a GaAs matrix depletion region have been calculated for application in the analysis of experimental data from deep-level transient spectroscopy (DLTS). The hybridization among metastable states localized in the InAs QD and continuum states in the GaAs substrate in the DLTS measurement is evaluated from the local densities of states. Two physical quantities have been calculated, the broadening of the metastable state localized in the InAs QD, i.e., the charge-transfer rates from the quantum dot to the substrate, and the corresponding hybridization coefficients. The metastable state is broadened significantly only when the bias is large enough, whereas the hybridization coefficients increase almost linearly with the bias. The effects of the direct Coulomb interactions and exchange energies among electrons initially confined in the QD have been included and found to be very significant. Increasing the number of electrons initially confined in the QD from 1 to 4, the charge-transfer rates increase by a factor of 1.8.
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