| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Borg, Mattias, et al.
(författare)
-
InAs/GaSb Heterostructure Nanowires for Tunnel Field-Effect Transistors.
- 2010
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:Online August 24, 2010, s. 4080-4085
-
Tidskriftsartikel (refereegranskat)abstract
- InAs/GaSb nanowire heterostructures with thin GaInAs inserts were grown by MOVPE and characterized by electrical measurements and transmission electron microscopy. Down-scaling of the insert thickness was limited because of an observed sensitivity of GaSb nanowire growth to the presence of In. By employing growth interrupts in between the InAs and GaInAs growth steps it was possible to reach an insert thickness down to 25 nm. Two-terminal devices show a diode behavior, where temperature-dependent measurements indicate a heterostructure barrier height of 0.5 eV, which is identified as the valence band offset between the InAs and GaSb. Three-terminal transistor structures with a top-gate positioned at the heterointerface show clear indications of band-to-band tunnelling.
|
|
| 6. |
- Borg, Mattias, et al.
(författare)
-
Influence of doping on the electronic transport in GaSb/InAs(Sb) nanowire tunnel devices
- 2012
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:4
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of various doping profiles on the electronic transport in GaSb/InAs(Sb) nanowire tunnel diodes is investigated. Zn-doping of the GaSb segment increases both the peak current density and the current level in reverse bias. Top-gated diodes exhibit peak current modulation with a threshold voltage which can be controlled by Zn-doping the InAs(Sb) segment. By intentionally n-doping the InAs(Sb) segment degenerate doping on both sides of the heterojunction can be achieved, as well as tunnel diodes with peak current of 420 kA/cm(2) at V-DS = 0.16V and a record-high current density of 3.6 MA/cm(2) at V-DS = -0.5V. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739082]
|
|
| 7. |
- Deppert, Knut, et al.
(författare)
-
Epitaxielle Kristallnadeln und -bäume
- 2005
-
Ingår i: Book of abstracts: DGKK-Jahrestagung, Köln, Germany (2005).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 8. |
|
|
| 9. |
- Dey, Anil, et al.
(författare)
-
High Current Density InAsSb/GaSb Tunnel Field Effect Transistors
- 2012
-
Ingår i: Device research conference. - 1548-3770. ; , s. 205-206
-
Konferensbidrag (refereegranskat)abstract
- Steep-slope devices, such as tunnel field-effect transistors (TFETs), have recently gained interest due to their potential for low power operation at room temperature. The devices are based on inter-band tunneling which could limit the on-current since the charge carriers must tunnel through a barrier to traverse the device. The InAs/GaSb heterostructure forms a broken type II band alignment which enables inter-band tunneling without a barrier, allowing high on-currents. We have recently demonstrated high current density (Ion,reverse = 17.5 mA/µm) nanowire Esaki diodes and in this work we investigate the potential of InAs/GaSb heterostructure nanowires to operate as TFETs. We present device characterization of InAs 0.85 Sb 0.15 /GaSb nanowire TFETs, which exhibit record-high on-current levels.
|
|
| 10. |
- Dey, Anil, et al.
(författare)
-
High-Current GaSb/InAs(Sb) Nanowire Tunnel Field-Effect Transistors
- 2013
-
Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 34:2, s. 211-213
-
Tidskriftsartikel (refereegranskat)abstract
- We present electrical characterization of GaSb/InAs(Sb) nanowire tunnel field-effect transistors. The broken band alignment of the GaSb/InAs(Sb) heterostructure is exploited to allow for interband tunneling without a barrier, leading to high ON-current levels. We report a maximum drive current of 310 μA/μm at Vds = 0.5 V. Devices with scaled gate oxides display transconductances up to gm = 250 mS/mm at Vds = 300 mV, which are normalized to the nanowire circumference at the axial heterojunction.
|
|
| 11. |
- Dey, Anil, et al.
(författare)
-
High-Performance InAs Nanowire MOSFETs
- 2012
-
Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 33:6, s. 791-793
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, we present a 15-nm-diameter InAs nanowire MOSFET with excellent on and off characteristics. An n-i-n doping profile was used to reduce the source and drain resistances, and an Al2O3/HfO2 bilayer was introduced in the high-k process. The nanowires exhibit high drive currents, up to 1.25 A/mm, normalized to the nanowire circumference, and current densities up to 34 MA/cm2 (VD = 0.5 V). For a nominal LG = 100 nm, we observe an extrinsic transconductance (gm) of 1.23 S/mm and a subthreshold swing of 93 mV/decade at VD = 10 mV.
|
|
| 12. |
- Dick Thelander, Kimberly, et al.
(författare)
-
Crystal Phase Engineering in Single InAs Nanowires.
- 2010
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:9, s. 3494-3499
-
Tidskriftsartikel (refereegranskat)abstract
- Achieving phase purity and control in III-V nanowires is a necessity for future nanowire-based device applications. Many works have focused on cleaning specific crystal phases of defects such as twin planes and stacking faults, using parameters such as diameter, temperature, and impurity incorporation. Here we demonstrate an improved method for crystal phase control, where crystal structure variations in single InAs nanowires are designed with alternating wurtzite (WZ) and zinc blende (ZB) segments of precisely controlled length and perfect interfaces. We also demonstrate the inclusion of single twin planes and stacking faults with atomic precision in their placement, designed ZB quantum dots separated by thin segments of WZ, acting as tunnel barriers for electrons, and structural superlattices (polytypic and twin plane). Finally, we present electrical data to demonstrate the applicability of these designed structures to investigation of fundamental properties. From electrical measurements we observe clear signatures of controlled structural quantum dots in nanowires. This method will be directly applicable to a wide range of nanowire systems.
|
|
| 13. |
- Ek, Martin, et al.
(författare)
-
Formation of the axial heterojunction in GaSb/InAs(Sb) nanowires with high crystal quality
- 2011
-
Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 11:10, s. 4588-4593
-
Tidskriftsartikel (refereegranskat)abstract
- Switching of the group-III element in III-V nanowire heterostructures is difficult due to the high solubility of group-III atoms in the Au seed particle. In addition, switching from Sb to a different group-V element has not been achieved in binary materials, largely due to its high solubility in Au. In MOVPE growth the use of Sb precursors presents further complications due to reactor background contamination. In this paper we demonstrate growth of GaSb/InAs(Sb) nanowire heterostructures with potential applications in tunneling devices, and study the processes occurring during the transition from GaSb to InAs growth. We show how the heterostructure can be grown with a sharp transition by taking advantage of a growth stop, which occurs naturally as the Au seed particle is emptied of Ga and filled with In. The remaining Sb background in the reactor during the InAs growth results in a finite Sb incorporation into this segment. This has the advantage of suppressing stacking faults in the InAs(Sb) segment, making the entire heterostructure a single zincblende crystal.
|
|
| 14. |
- Fahlvik Svensson, Sofia, et al.
(författare)
-
Control and understanding of kink formation in InAs-InP heterostructure nanowires.
- 2013
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 24:34
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowire heterostructures are of special interest for band structure engineering due to an expanded range of defect-free material combinations. However, the higher degree of freedom in nanowire heterostructure growth comes at the expense of challenges related to nanowire-seed particle interactions, such as undesired composition, grading and kink formation. To better understand the mechanisms of kink formation in nanowires, we here present a detailed study of the dependence of heterostructure nanowire morphology on indium pressure, nanowire diameter, and nanowire density. We investigate InAs-InP-InAs heterostructure nanowires grown with chemical beam epitaxy, which is a material system that allows for very abrupt heterointerfaces. Our observations indicate that the critical parameter for kink formation is the availability of indium, and that the resulting morphology is also highly dependent on the length of the InP segment. It is shown that kinking is associated with the formation of an inclined facet at the interface between InP and InAs, which destabilizes the growth and leads to a change in growth direction. By careful tuning of the growth parameters, it is possible to entirely suppress the formation of this inclined facet and thereby kinking at the heterointerface. Our results also indicate the possibility of producing controllably kinked nanowires with a high yield.
|
|
| 15. |
- Ganjipour, Bahram, et al.
(författare)
-
Carrier control and transport modulation in GaSb/InAsSb core/shell nanowires
- 2012
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:10
-
Tidskriftsartikel (refereegranskat)abstract
- We report transport studies of GaSb/InAs core/shell nanowires. It is shown that with increasing InAs shell thickness, it is possible to tune the carrier concentrations and transport in the structures from p-type (core-dominated) to n-type (shell dominated). For nanowires with an intermediate shell thickness (5-7 nm), we show that the transport is ambipolar, such that an applied top-gate potential can provide further control of carrier type and transport path. In this range, the nature of the GaSb-InAs junction also changes from broken gap (semimetal) to staggered (narrow bandgap) with a small decrease in shell thickness. From a device point of view, we demonstrate that the presence of a thin (<3 nm) InAs shell improves p-type GaSb nanowire transistor characteristics. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4749283]
|
|
| 16. |
- Ganjipour, Bahram, et al.
(författare)
-
Electrical properties of GaSb/InAsSb core/shell nanowires
- 2014
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:42
-
Tidskriftsartikel (refereegranskat)abstract
- Temperature dependent electronic properties of GaSb/InAsSb core/shell and GaSb nanowires have been studied. Results from two-probe and four-probe measurements are compared to distinguish between extrinsic (contact-related) and intrinsic (nanowire) properties. It is found that a thin (2-3 nm) InAsSb shell allows low barrier charge carrier injection to the GaSb core, and that the presence of the shell also improves intrinsic nanowire mobility and conductance in comparison to bare GaSb nanowires. Maximum intrinsic field effect mobilities of 200 and 42 cm(2) Vs(-1) were extracted for the GaSb/InAsSb core/shell and bare-GaSb NWs at room temperature, respectively. The temperature-dependence of the mobility suggests that ionized impurity scattering is the dominant scattering mechanism in bare GaSb while phonon scattering dominates in core/shell nanowires. Top-gated field effect transistors were fabricated based on radial GaSb/InAsSb heterostructure nanowires with shell thicknesses in the range 5-7 nm. The fabricated devices exhibited ambipolar conduction, where the output current was studied as a function of AC gate voltage and frequency. Frequency doubling was experimentally demonstrated up to 20 kHz. The maximum operating frequency was limited by parasitic capacitance associated with the measurement chip geometry.
|
|
| 17. |
|
|
| 18. |
- Ganjipour, Bahram, et al.
(författare)
-
High current density Esaki tunnel diodes based on GaSb-InAsSb heterostructure nanowires
- 2011
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:10, s. 4222-4226
-
Tidskriftsartikel (refereegranskat)abstract
- We present electrical characterization of broken gap GaSb-InAsSb nanowire heterojunctions. Esaki diode characteristics with maximum reverse current of 1750 kA/cm2 at 0.50 V, maximum peak current of 67 kA/cm2 at 0.11 V, and peak-to-valley ratio (PVR) of 2.1 are obtained at room temperature. The reverse current density is comparable to that of state-of-the-art tunnel diodes based on heavily doped p-n junctions. However, the GaSb-InAsSb diodes investigated in this work do not rely on heavy doping, which permits studies of transport mechanisms in simple transistor structures processed with high-κ gate dielectrics and top-gates. Such processing results in devices with improved PVR (3.5) and stability of the electrical properties.
|
|
| 19. |
- Gluschke, Jan-Göran, et al.
(författare)
-
Characterization of Ambipolar GaSb/InAs Core-Shell Nanowires by Thermovoltage Measurements.
- 2015
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 9:7, s. 7033-7040
-
Tidskriftsartikel (refereegranskat)abstract
- In semiconductor heterostructures with a type II band alignment, such as GaSb-InAs, conduction can be tuned from electron- to hole-dominated using an electrostatic gate. However, traditional conductance measurements give no direct information on the carrier type, and thus limit the ability to distinguish transport effects originating from the two materials. Here, we employ thermovoltage measurements to GaSb/InAs core-shell nanowires, and reliably identify the dominant carrier type at room temperature as well as in the quantum transport regime at 4.2 K, even in cases where the conductance measurement does not allow for such a distinction. In addition, we show that theoretical modeling using the conductance data as input can reproduce the measured thermovoltage under the assumption that electron and hole states shift differently in energy with the applied gate voltage.
|
|
| 20. |
- Gorji, Sepideh, et al.
(författare)
-
Demonstration of Defect-Free and Composition Tunable Ga(x)In(1-x)Sb Nanowires.
- 2012
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 12:9, s. 4914-4919
-
Tidskriftsartikel (refereegranskat)abstract
- The Ga(x)In(1-x)Sb ternary system has many interesting material properties, such as high carrier mobilities and a tunable range of bandgaps in the infrared. Here we present the first report on the growth and compositional control of Ga(x)In(1-x)Sb material grown in the form of nanowires from Au seeded nanoparticles by metalorganic vapor phase epitaxy. The composition of the grown Ga(x)In(1-x)Sb nanowires is precisely controlled by tuning the growth parameters where x varies from 1 to ∼0.3. Interestingly, the growth rate of the Ga(x)In(1-x)Sb nanowires increases with diameter, which we model based on the Gibbs-Thomson effect. Nanowire morphology can be tuned from high to very low aspect ratios, with perfect zinc blende crystal structure regardless of composition. Finally, electrical characterization on nanowire material with a composition of Ga(0.6)In(0.4)Sb showed clear p-type behavior.
|
|
| 21. |
|
|
| 22. |
- Namazi, Luna, et al.
(författare)
-
Selective GaSb radial growth on crystal phase engineered InAs nanowires.
- 2015
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 7:23, s. 10472-10481
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we have developed InAs nanowire templates, with designed zinc blende and wurtzite segments, for selective growth of radial GaSb heterostructures using metal organic vapor phase epitaxy. We find that the radial growth rate of GaSb is determined by the crystal phase of InAs, and that growth is suppressed on InAs segments with a pure wurtzite crystal phase. The morphology and the thickness of the grown shell can be tuned with full control by the growth conditions. We demonstrate that multiple distinct core-shell segments can be designed and realized with precise control over their length and axial position. Electrical measurements confirm that suppression of shell growth is possible on segments with wurtzite structures. This growth method enables new functionalities in structures formed by using bottom-up techniques, with complexity beyond that attainable by using top-down techniques.
|
|
| 23. |
|
|
| 24. |
- Persson, Olof, et al.
(författare)
-
Scanning Tunneling Spectroscopy on InAs-GaSb Esaki Diode Nanowire Devices during Operation.
- 2015
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:6, s. 3684-3691
-
Tidskriftsartikel (refereegranskat)abstract
- Using a scanning tunneling and atomic force microscope combined with in-vacuum atomic hydrogen cleaning we demonstrate stable scanning tunneling spectroscopy (STS) with nanoscale resolution on electrically active nanowire devices in the common lateral configuration. We use this method to map out the surface density of states on both the GaSb and InAs segments of GaSb-InAs Esaki diodes as well as the transition region between the two segments. Generally the surface shows small bandgaps centered around the Fermi level, which is attributed to a thin multielement surface layer, except in the diode transition region where we observe a sudden broadening of the bandgap. By applying a bias to the nanowire we find that the STS spectra shift according to the local nanoscale potential drop inside the wire. Importantly, this shows that we have a nanoscale probe with which we can infer both surface electronic structure and the local potential inside the nanowire and we can connect this information directly to the performance of the imaged device.
|
|
| 25. |
- Samuelson, Lars, et al.
(författare)
-
Semiconductor nanowires for 0D and 1D physics and applications
- 2004
-
Ingår i: Physica E: Low-Dimensional Systems and Nanostructures. - : Elsevier BV. - 1386-9477. ; 25:2-3, s. 313-318
-
Tidskriftsartikel (refereegranskat)abstract
- During the last 5 years the potential for applications of semiconductor nanowires has grown rapidly via the development of methods for catalytically induced nanowire growth using the, so-called vapor-liquid-solid (VLS) growth mode. The VLS method offers a high degree of control of parameters such as position, diameter, length and composition, including the realization of atomically abrupt heterostructure interfaces inside a nanowire. In this review, we summarize the progress and the standing of our research from the point of view of controlled growth, structural and electronic properties and in terms of different families of devices which have been possible to realize. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 26. |
|
|
| 27. |
- Schukfeh, Muhammed Ihab, et al.
(författare)
-
Conductance Enhancement of InAs/InP Heterostructure Nanowires by Surface Functionalization with Oligo(phenylene vinylene)s
- 2013
-
Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 7:5, s. 4111-4118
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the electronic transport through 3 mu m long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I-V characteristic with significantly increased currents of up to 1 mu A at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.
|
|
| 28. |
- Schukfeh, Muhammed Ihab, et al.
(författare)
-
Selective etching of InP in InAs/InP nanowires resulting in 11 nm nanogaps
- 2016
-
Ingår i: IEEE-NANO 2015 - 15th International Conference on Nanotechnology. - 9781467381550 ; , s. 1489-1492
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate a wet chemical method to selectively etch InP segments within InAs/InP heterostructure nanowires based on a photo-assisted HAc/HBr solution etching process. We successfully etched InP segments ranging from 60 nm down to about 10 nm in size.
|
|
| 29. |
- Sun, Rong, et al.
(författare)
-
Sn-Seeded GaAs Nanowires as Self-Assembled Radial p-n Junctions
- 2015
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:6, s. 3757-3762
-
Tidskriftsartikel (refereegranskat)abstract
- The widespread use of Au as a seed particle in the fabrication of semiconductor nanowires presents a fundamental limitation to the potential incorporation of such nanostructures into electronic devices. Although several other growth techniques have been demonstrated, the use of alternative seed particle metals remains an underexplored but potentially very promising way to influence the properties of the resulting nanowires while simultaneously avoiding gold. In this Letter, we demonstrate the use of Sn as a seed particle metal for GaAs nanowires grown by metal-organic vapor phase epitaxy. We show that vertically aligned and stacking defect-free GaAs nanowires can be grown with very high yield. The resulting nanowires exhibit Esaki diode behavior, attributed to very high n-doping of the nanowire core with Sn, and simultaneous C-doping of the radial overgrowth. These results demonstrate that the use of alternative seed particle metals is a potentially important area to explore for developing nanowire materials with controlled material properties.
|
|
| 30. |
- Thelander, Claes, et al.
(författare)
-
Effects of crystal phase mixing on the electrical properties of InAs nanowires
- 2011
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:April 29, 2011, s. 2424-2429
-
Tidskriftsartikel (refereegranskat)abstract
- We report a systematic study of the relationship between crystal quality and electrical properties of InAs nanowires grown by MOVPE and MBE, with crystal structure varying from wurtzite to zinc blende. We find that mixtures of these phases can exhibit up to 2 orders of magnitude higher resistivity than single-phase nanowires, with a temperature-activated transport mechanism. However, it is also found that defects in the form of stacking faults and twin planes do not significantly affect the resistivity. These findings are important for nanowire-based devices, where uncontrolled formation of particular polytype mixtures may lead to unacceptable device variability.
|
|
| 31. |
- Thelander, Claes, et al.
(författare)
-
Electrical properties of InAs1-xSbx and InSb nanowires grown by molecular beam epitaxy
- 2012
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:23
-
Tidskriftsartikel (refereegranskat)abstract
- Results of electrical characterization of Au nucleated InAs1-xSbx nanowires grown by molecular beam epitaxy are reported. An almost doubling of the extracted field effect mobility compared to reference InAs nanowires is observed for a Sb content of x = 0.13. Pure InSb nanowires on the other hand show considerably lower, and strongly diameter dependent, mobility values. Finally, InAs of wurtzite crystal phase overgrown with an InAs1-xSbx shell is found to have a substantial positive shift in threshold voltage compared to reference nanowires. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4726037]
|
|
| 32. |
- Thelander, Claes, et al.
(författare)
-
The electrical and structural properties of n-type InAs nanowires grown from metal-organic precursors.
- 2010
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:20
-
Tidskriftsartikel (refereegranskat)abstract
- The electrical and structural properties of 111B-oriented InAs nanowires grown using metal-organic precursors have been studied. On the basis of electrical measurements it was found that the trends in carbon incorporation are similar to those observed in the layer growth, where an increased As/In precursor ratio and growth temperature result in a decrease in carbon-related impurities. Our results also show that the effect of non-intentional carbon doping is weaker in InAs nanowires compared to bulk, which may be explained by lower carbon incorporation in the nanowire core. We determine that differences in crystal quality, here quantified as the stacking fault density, are not the primary cause for variations in resistivity of the material studied. The effects of some n-dopant precursors (S, Se, Si, Sn) on InAs nanowire morphology, crystal structure and resistivity were also investigated. All precursors result in n-doped nanowires, but high precursor flows of Si and Sn also lead to enhanced radial overgrowth. Use of the Se precursor increases the stacking fault density in wurtzite nanowires, ultimately at high flows leading to a zinc blende crystal structure with strong overgrowth and very low resistivity.
|
|
| 33. |
|
|
| 34. |
- Webb, James, et al.
(författare)
-
High resolution scanning gate microscopy measurements on InAs/GaSb nanowire Esaki diode devices
- 2014
-
Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 7:6, s. 877-887
-
Tidskriftsartikel (refereegranskat)abstract
- Gated transport measurements are the backbone of electrical characterization of nanoscale electronic devices. Scanning gate microscopy (SGM) is one such gating technique that adds crucial spatial information, accessing the localized properties of semiconductor devices. Nanowires represent a central device concept due to the potential to combine very different materials. However, SGM on semiconductor nanowires has been limited to a resolution in the 50-100 nm range. Here, we present a study by SGM of newly developed III-V semiconductor nanowire InAs/GaSb heterojunction Esaki tunnel diode devices under ultra-high vacuum. Sub-5 nm resolution is demonstrated at room temperature via use of quartz resonator atomic force microscopy sensors, with the capability to resolve InAs nanowire facets, the InAs/GaSb tunnel diode transition and nanoscale defects on the device. We demonstrate that such measurements can rapidly give important insight into the device properties via use of a simplified physical model, without the requirement for extensive calculation of the electrostatics of the system. Interestingly, by precise spatial correlation of the device electrical transport properties and surface structure we show the position and existence of a very abrupt (<10 nm) electrical transition across the InAs/GaSb junction despite the change in material composition occurring only over 30-50 nm. The direct and simultaneous link between nanostructure composition and electrical properties helps set important limits for the precision in structural control needed to achieve desired device performance.
|
|
| 35. |
- Wu, Phillip, et al.
(författare)
-
Large Thermoelectric Power Factor Enhancement Observed in InAs Nanowires.
- 2013
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:9, s. 4080-4086
-
Tidskriftsartikel (refereegranskat)abstract
- We report the observation of a thermoelectric power factor in InAs nanowires that exceeds that predicted by a single-band bulk model by up to an order of magnitude at temperatures below about 20 K. We attribute this enhancement effect not to the long-predicted 1D subband effects but to quantum-dot-like states that form in electrostatically nonuniform nanowires as a result of interference between propagating states and 0D resonances.
|
|
| 36. |
- Aspegren, Markus, et al.
(författare)
-
Perfect Zeeman Anisotropy in Rotationally Symmetric Quantum Dots with Strong Spin-Orbit Interaction
- 2024
-
Ingår i: Nano Letters. - 1530-6984. ; 24:26, s. 7927-7933
-
Tidskriftsartikel (refereegranskat)abstract
- In nanoscale structures with rotational symmetry, such as quantum rings, the orbital motion of electrons combined with a spin-orbit interaction can produce a very strong and anisotropic Zeeman effect. Since symmetry is sensitive to electric fields, ring-like geometries provide an opportunity to manipulate magnetic properties over an exceptionally wide range. In this work, we show that it is possible to form rotationally symmetric confinement potentials inside a semiconductor quantum dot, resulting in electron orbitals with large orbital angular momentum and strong spin−orbit interactions. We find complete suppression of Zeeman spin splitting for magnetic fields applied in the quantum dot plane, similar to the expected behavior of an ideal quantum ring. Spin splitting reappears as orbital interactions are activated with symmetry-breaking electric fields. For two valence electrons, representing a common basis for spin-qubits, we find that modulating the rotational symmetry may offer new prospects for realizing tunable protection and interaction of spin-orbital states.
|
|
| 37. |
- Barker, David, et al.
(författare)
-
Experimental Verification of the Work Fluctuation-Dissipation Relation for Information-to-Work Conversion
- 2022
-
Ingår i: Physical Review Letters. - 0031-9007. ; 128:4
-
Tidskriftsartikel (refereegranskat)abstract
- We study experimentally work fluctuations in a Szilard engine that extracts work from information encoded as the occupancy of an electron level in a semiconductor quantum dot. We show that as the average work extracted per bit of information increases toward the Landauer limit Formula Presented, the work fluctuations decrease in accordance with the work fluctuation-dissipation relation. We compare the results to a protocol without measurement and feedback and show that when no information is used, the work output and fluctuations vanish simultaneously, contrasting the information-to-energy conversion case where increasing amount of work is produced with decreasing fluctuations. Our study highlights the importance of fluctuations in the design of information-to-work conversion processes.
|
|
| 38. |
|
|
| 39. |
|
|
| 40. |
- Björk, Mikael, et al.
(författare)
-
Few-electron quantum dots in nanowires
- 2004
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 4:9, s. 1621-1625
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate transport spectroscopy on bottom-up grown few-electron quantum dots in semiconductor nanowires. The dots are defined by InP double barrier heterostructures in InAs nanowires catalytically grown from nanoparticles. By changing the dot size, we can design devices ranging from single-electron transistors to few-electron quantum dots. In the latter case, electrons can be added one by one to the dots from 0 to similar to50 electrons while maintaining an almost constant charging energy, with addition spectra of the devices displaying shell structures as a result of spin and orbital degeneracies. The reduced dimensionality of the nanowire emitter gives rise to pronounced resonant tunneling peaks, where a gate can be used to control the peak positions.
|
|
| 41. |
- Björk, Mikael, et al.
(författare)
-
Nanowire resonant tunneling diodes
- 2002
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 81:23, s. 4458-4460
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconductor heterostructures and their implementation into electronic and photonic devices have had tremendous impact on science and technology. In the development of quantum nanoelectronics, one-dimensional (1D) heterostructure devices are receiving a lot of interest. We report here functional 1D resonant tunneling diodes obtained via bottom-up assembly of designed segments of different semiconductor materials in III/V nanowires. The emitter, collector, and the central quantum dot are made from InAs and the barrier material from InP. Ideal resonant tunneling behavior, with peak-to-valley ratios of up to 50:1 and current densities of 1 nA/mum(2) was observed at low temperatures. (C) 2002 American Institute of Physics.
|
|
| 42. |
- Björk, Mikael, et al.
(författare)
-
One-dimensional heterostructures in semiconductor nanowhiskers
- 2002
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 80:6, s. 1058-1060
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the growth of designed heterostructures placed within semiconductor nanowhiskers, exemplified by the InAs/InP material system. Based on transmission electron microscopy, we deduce the interfaces between InAs and InP to be atomically sharp. Electrical measurements of thermionic emission across an 80-nm-wide InP heterobarrier, positioned inside InAs whiskers 40 nm in diameter, yield a barrier height of 0.6 eV. On the basis of these results, we propose new branches of physics phenomena as well as new families of device structures that will now be possible to realize and explore.
|
|
| 43. |
- Björk, Mikael, et al.
(författare)
-
One-dimensional steeplechase for electrons realized
- 2002
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:2, s. 87-89
-
Tidskriftsartikel (refereegranskat)abstract
- We report growth of one-dimensional semiconductor nanocrystals, nanowhiskers, in which segments of the whisker with different composition are formed, illustrated by InAs whiskers containing segments of InP. Our conditions for growth allow the formation of abrupt interfaces and heterostructure barriers of thickness from a few monolayers to 100s of nanometers, thus creating a one-dimensional landscape along which the electrons move. The crystalline perfection, the quality of the interfaces, and the variation in the lattice constant are demonstrated by high-resolution transmission electron microscopy, and the conduction band off-set of 0.6 eV is deduced from the current due to thermal excitation of electrons over an InP barrier.
|
|
| 44. |
|
|
| 45. |
|
|
| 46. |
- Chen, I. Ju, et al.
(författare)
-
Conduction Band Offset and Polarization Effects in InAs Nanowire Polytype Junctions
- 2017
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:2, s. 902-908
-
Tidskriftsartikel (refereegranskat)abstract
- Although zinc-blende (ZB) and wurtzite (WZ) structures differ only in the atomic stacking sequence, mixing of crystal phases can strongly affect the electronic properties, a problem particularly common to bottom up-grown nanostructures. A lack of understanding of the nature of electronic transport at crystal phase junctions thus severely limits our ability to develop functional nanowire devices. In this work we investigated electron transport in InAs nanowires with designed mixing of crystal structures, ZB/WZ/ZB, by temperature-dependent electrical measurements. The WZ inclusion gives rise to an energy barrier in the conduction band. Interpreting the experimental result in terms of thermionic emission and using a drift-diffusion model, we extracted values for the WZ/ZB band offset, 135 ± 10 meV, and interface sheet polarization charge density on the order of 10-3 C/m2. The extracted polarization charge density is 1-2 orders of magnitude smaller than previous experimental results, but in good agreement with first principle calculation of spontaneous polarization in WZ InAs. When the WZ length is reduced below 20 nm, an effective barrier lowering is observed, indicating the increasing importance of tunneling transport. Finally, we found that band-bending at ZB/WZ junctions can lead to bound electron states within an enclosed WZ segment of sufficient length, evidenced by our observation of Coulomb blockade at low temperature. These findings provide critical input for modeling and designing the electronic properties of novel functional devices, such as nanowire transistors, where crystal polytypes are commonly found.
|
|
| 47. |
- Chen, I. Ju, et al.
(författare)
-
Hot-Carrier Extraction in Nanowire-Nanoantenna Photovoltaic Devices
- 2020
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 20:6, s. 4064-4072
-
Tidskriftsartikel (refereegranskat)abstract
- Nanowires bring new possibilities to the field of hot-carrier photovoltaics by providing flexibility in combining materials for band engineering and using nanophotonic effects to control light absorption. Previously, an open-circuit voltage beyond the Shockley-Queisser limit was demonstrated in hot-carrier devices based on InAs-InP-InAs nanowire heterostructures. However, in these first experiments, the location of light absorption, and therefore the precise mechanism of hot-carrier extraction, was uncontrolled. In this Letter, we combine plasmonic nanoantennas with InAs-InP-InAs nanowire devices to enhance light absorption within a subwavelength region near an InP energy barrier that serves as an energy filter. From photon-energy- and irradiance-dependent photocurrent and photovoltage measurements, we find that photocurrent generation is dominated by internal photoemission of nonthermalized hot electrons when the photoexcited electron energy is above the barrier and by photothermionic emission when the energy is below the barrier. We estimate that an internal quantum efficiency up to 0.5-1.2% is achieved. Insights from this study provide guidelines to improve internal quantum efficiencies based on nanowire heterostructures.
|
|
| 48. |
- Chen, I. Ju, et al.
(författare)
-
Thermoelectric Power Factor Limit of a 1D Nanowire
- 2018
-
Ingår i: Physical Review Letters. - 0031-9007. ; 120:17
-
Tidskriftsartikel (refereegranskat)abstract
- In the past decade, there has been significant interest in the potentially advantageous thermoelectric properties of one-dimensional (1D) nanowires, but it has been challenging to find high thermoelectric power factors based on 1D effects in practice. Here we point out that there is an upper limit to the thermoelectric power factor of nonballistic 1D nanowires, as a consequence of the recently established quantum bound of thermoelectric power output. We experimentally test this limit in quasiballistic InAs nanowires by extracting the maximum power factor of the first 1D subband through I-V characterization, finding that the measured maximum power factors conform to the theoretical limit. The established limit allows the prediction of the achievable power factor of a specific nanowire material system with 1D electronic transport based on the nanowire dimension and mean free path. The power factor of state-of-the-art semiconductor nanowires with small cross section and high crystal quality can be expected to be highly competitive (on the order of mW/m K2) at low temperatures. However, they have no clear advantage over bulk materials at, or above, room temperature.
|
|
| 49. |
- Debbarma, Rousan, et al.
(författare)
-
Effects of Parity and Symmetry on the Aharonov-Bohm Phase of a Quantum Ring
- 2021
-
Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992.
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigate the properties of one-dimensional quantum rings that form near the surface of nanowire quantum dots. In agreement with theoretical predictions, we observe the appearance of forbidden gaps in the evolution of states in a magnetic field as the symmetry of a quantum ring is reduced. For a twofold symmetry, our experiments confirm that orbital states are grouped pairwise. Here, a π-phase shift can be introduced in the Aharonov-Bohm relation by controlling the relative orbital parity using an electric field. Studying rings with higher symmetry, we note exceptionally large orbital contributions to the effective g-factor (up to 300), which are many times higher than those previously reported. These findings show that the properties of a phase-coherent system can be significantly altered by the nanostructure symmetry and its interplay with wave function parity.
|
|
| 50. |
|
|
