| 1. |
- Achermann, M, et al.
(författare)
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Carrier dynamics around nano-scale Schottky contacts: a femtosecond near-field study
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1-4, s. 513-516
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Tidskriftsartikel (refereegranskat)abstract
- We report spatially and time-resolved measurements of ultrafast carrier dynamics around buried nano-scale Schottky contacts, performed with a novel femtosecond near-field scanning optical microscope. The experimental results are modeled by a self-consistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. We show that the built-in field suppresses electron transport towards and trapping into the metal particles at lower optically excited carrier densities. In contrast, efficient electron trapping into the metal occurs at higher electron densities, which screen the built-in field, allowing for efficient transport of electrons towards the Schottky contact. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Ohki, S, et al.
(författare)
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A study of estimation method for conduction band offset in semiconductor heterostructure by using triple-barrier resonant tunneling diodes
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1-4, s. 288-293
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Tidskriftsartikel (refereegranskat)abstract
- A method for evaluating a band offset of a heterojunction is proposed by measuring temperature dependence of current-voltage (I-V) characteristics in triple-barrier resonant tunneling diodes (TBRTDs). The method was applied for investigating a conduction band offset by using GaAs0.25P0.75/GaAs TBRTDs with thin strain heterobarriers grown by MOCVD and DeltaE(c) was estimated as 200-240 meV. In the strain-barrier TBRTDs, negative differential resistance was observed below 100 K. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Wernersson, Lars-Erik, et al.
(författare)
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Thin layers of GaInP, GaP and GaAsP in metalorganic vapour phase epitaxy-grown resonant tunnelling diodes
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1, s. 252-257
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the epitaxial growth and electrical performance of Al-free, GaAs-based, resonant tunnelling diodes (RTDs) including thin barriers of GaInP, GO, or GaAsxP1-x. n-Type tunnelling diodes have been fabricated and the symmetry in the current-voltage (I-V) characteristics, as well as the peak-to-valley ratios, are found to be sensitive probes for the inter-face quality in the heterostructures. For GaInP RTDs, we show that the introduction of Gap intermediate layers is crucial for the realisation. of a useful tunnelling current. RTDs including thin barriers (less than about 10 monolayers (ML)) of Gap are realised, but the strong mismatch between the materials limit the useful thickness. Finally, RTDs with GaAslambdaP1-x alloys are fabricated showing the best peak-to-valley ratio of the diodes (about 5), as well as a symmetric I-V characteristics. The electrical data are further compared to studies by transmission electron microscopy (TEM) in the various material systems.
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| 4. |
- Yong, Zhihua, et al.
(författare)
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Tuning oxygen vacancies and resistive switching properties in ultra-thin HfO2 RRAM via TiN bottom electrode and interface engineering
- 2021
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Ingår i: Applied Surface Science. - : Elsevier BV. - 1873-5584 .- 0169-4332. ; 551
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Tidskriftsartikel (refereegranskat)abstract
- Resistive random access memory (RRAM) technologies based on non-volatile resistive filament redox switching oxides have the potential of drastically improving the performance of future mass-storage solutions. However, the physico-chemical properties of the TiN bottom metal electrode (BME) can significantly alter the resistive switching (RS) behavior of the oxygen-vacancy RRAM devices, yet the correlation between RS and the physico-chemical properties of TiN and HfOx/TiN interface remains unclear. Here, we establish this particular correlation via detailed material and electrical characterization for the purpose of achieving further performance enhancement of the stack integration. Two types of RRAM stacks were fabricated where the TiN BME was fabricated by physical vapor deposition (PVD) and atomic layer deposition (ALD), respectively. The HfOx layer in HfOx/PVD-TiN is more oxygen deficient than that of the HfOx/ALD-TiN because of more defective PVD-TiN and probably because pristine ALD-TiN has a thicker TiO2 overlayer. Higher concentration of oxygen vacancies induces a larger magnitude of band bending at the HfOx/PVD-TiN interface and leads to the formation of a higher Schottky barrier. Pulsed endurance measurements of up to 106 switches, with 10 μA ± 1.0 V pulses, demonstrate the potential of the studied ultra-thin-HfOx/TiN device stack for dense, large scale, and low-power memory integration.
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