| 11. |
- Athle, Robin, et al.
(författare)
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Improved Endurance of Ferroelectric HfxZr1–xO2 Integrated on InAs Using Millisecond Annealing
- 2022
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 9:27
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Tidskriftsartikel (refereegranskat)abstract
- Ferroelectric HfxZr1–xO2 (HZO) is typically achieved by crystallization of an amorphous thin film via rapid thermal processing (RTP) at time scales of seconds to minutes. For integration on III–V semiconductors, this approach can severely degrade the sensitive HZO/III–V interface. To evaluate whether a reduced thermal budget can improve the interface quality, millisecond duration thermal anneals are utilized using a flash lamp annealer (FLA) on HZO/InAs capacitors. Through thorough electrical characterization such as polarization hysteresis, endurance, and capacitance-voltage measurements, as well as synchrotron-based chemical interface characterization, the FLA and RTP treatments are compared and the FLA results are found in lower interface defect density and higher endurance, but also have generally lower remanent polarization (Pr) compared to RTP. Additionally, ways to achieve high Pr and low interface defect density using multiple lower energy flashes, as well as by pre-crystallization during the ALD growth step are investigated. Using FLA, Pr exceeding 20 µC cm−2 is achieved, with extended endurance properties compared to RTP treatment and a considerably decreased defect density, indicative of a higher quality HZO/InAs interface. This work presents valuable insight into the successful integration of ferroelectric HZO on low thermal budget III–V semiconductors.
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| 12. |
- Athle, Robin, et al.
(författare)
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Top Electrode Engineering for Freedom in Design and Implementation of Ferroelectric Tunnel Junctions Based on Hf1- xZrxO2
- 2022
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 4:3, s. 1002-1009
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Tidskriftsartikel (refereegranskat)abstract
- Ferroelectric tunnel junctions (FTJs) based on ultrathin HfO2 have great potential as a fast and energy-efficient memory technology compatible with complementary metal oxide semiconductors. FTJs consist of a ferroelectric film sandwiched between two distinct electrodes, the properties of which are intricately linked to the electrical properties of the FTJs. Here we utilize a W crystallization electrode (CE) to achieve a high and reproducible remanent polarization, combined with a metal replacement process in which the W is carefully removed and replaced by another top electrode (TE). In this way we separate the ferroelectric film properties from the device design and can thereby evaluate the effect of the TE work function (WF) and conduction band electron density (ne) on the tunneling electroresistance (TER) and device reliability. We compare FTJs designed with a TiN bottom electrode and W, Cr, or Ni TE and find that the use of high electron density metals such as Ni or Cr as TE allows for an improved TER, albeit at the cost of reliability due to a large built-in electric field. To bypass this effect, a bilayer Cr/Ni TE is implemented, which allows for a high TER and minimal built-in field, leading to excellent retention and endurance beyond 108 cycles. The results presented here thus highlight a process flow for reliable design and implementation of FTJs.
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| 13. |
- Berdnikov, Yury, et al.
(författare)
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Broadening of length distributions of Au-catalyzed InAs nanowires
- 2016
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Ingår i: State-of-the-Art Trends of Scientific Research of Artificial and Natural Nanoobjects, STRANN 2016: Proceedings of the 5th International Conference "State-of-the-Art Trends of Scientific Research of Artificial and Natural Nanoobjects". - : Author(s). - 9780735414051 ; 1748
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Konferensbidrag (refereegranskat)abstract
- We investigate kinetic broadening effects on the length distributions of gold-catalyzed InAs nanowires having different diameters. It is shown that the length distributions acquire bimodal shape when the longest nanowires exceed the diffusion length of indium adatoms on the nanowire sidewalls. Later on, the length distributions recover unimodal shapes. We develop a theoretical model that is capable of describing the observed behaviors by accounting for the diffusion-induced character of the vapor-liquid-solid growth.
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| 14. |
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| 15. |
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| 16. |
- Borg, Mattias
(författare)
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Antimonide Heterostructure Nanowires - Growth, Physics and Devices
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Abstract in UndeterminedThis thesis investigates the growth and application of antimonide heterostructure nanowires for low-power electronics. In the first part of the thesis, GaSb, InSb and InAsSb nanowire growth is presented, and the distinguishing features of the growth are described. It is found that the presence of Sb results in more than 50 at. % group-III concentration in the Au seed particle on top of the nanowires. It is further concluded that the effective V/III ratio inside the seed particle is reduced compared to the outside. This enables the suppression of radial growth with remaining high axial growth rate. Furthermore, the low effective V/III ratio may affect the crystal structure formation, which is pure Zinc-blende in all investigated Sb-based nanowires. The strong segregating properties of Sb results in a strong Sb memory effect, and a difficulty to nucleate Sb-based nanowires directly on substrates.The second part of the thesis deals with the growth and application of GaSb/InAs(Sb) nanowires for tunnel device applications. The GaSb/InAs(Sb) nanowire heterojunction has a defect-free crystal structure with an extremely abrupt heterojunction due to an inherent delay before the initiation of InAs(Sb) growth. The Sb carry-over from the GaSb growth step into the InAs growth leads to a high Sb background in the InAs(Sb) segment. The diameter of the heterojunction can be reduced below 30 nm by an in-situ annealing treatment, in which material is selectively etched from the region near the heterojunction.The performance of GaSb/InAs(Sb) tunnel diodes is modeled and measured on fabricated single nanowire devices. The diodes exhibit peak current levels of 67 kA/cm^{2} , peak-to-valley current ratio between 2 and 3 at room temperature and a tunnel current at V_{D} = -0.5 V of 1.7 MA/cm^{2} . The expected performance of GaSb/InAs(Sb) tunnel field-effect transistors is discussed and preliminary measurement data on top-gated devices with 300 nm gate length is also presented.
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| 17. |
- Borg, Mattias, et al.
(författare)
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Autonomy in PhD-education – Supervising for Independence
- 2016
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Ingår i: LTHs 9:e Pedagogiska Inspirationskonferens. ; , s. 9-13
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Konferensbidrag (refereegranskat)abstract
- According to the Swedish higher ordinance of education the development of autonomy of PhD students is of high importance. Graduates should be able to formulate new ideas and to independently assess and evaluate scientific results. Therefore it is interesting to investigate how the relationship between student and supervisor impacts the development of autonomy. In this work, we have evaluated the impact of the supervision relationship by a supervisor/studentalignment test (N=25) where both students and their supervisors perform a self-evaluation of the student’s level of autonomy and the supervisor’s supervision style. The test results show that the autonomy is greater for students with longer experience and also more aligned with the level of autonomy as perceived by their supervisors. The misalignment between the assessment done by students and supervisors decreases with age and time spent as a PhD student. However, we find that the misalignment increases when supervisors have many concurrent PhD students. We observe no statistical differences with respect to gender or nationality.
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| 18. |
- Borg, Mattias, et al.
(författare)
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Characterization of GaSb nanowires grown by MOVPE
- 2008
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Ingår i: Journal of Chrystal Growth. - : Elsevier BV. - 0022-0248. ; 310:23, s. 5119-5122
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Konferensbidrag (refereegranskat)abstract
- We report the growth and characterization of GaSb nanowires grown by MOVPE. The structural properties of the nanowires are investigated by the means of transmission electron microscopy, X-ray diffraction and single nanowire photoluminescence. The measurements confirm a high material quality in the GaSb nanowires. Also, a back-gated nanowire transistor structure is used to extract values for the polarity and resistivity of the GaSb. Finally, a simple kinetic model is presented to explain the non-linear time dependence of the GaSb nanowire growth. (C) 2008 Elsevier B.V. All rights reserved.
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| 19. |
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| 20. |
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