GaN Nanoribbons Research Articles

Ab-Initio Calculation of Electronic Properties of Doped GaN Nanoribbon

In this study, the electronic and magnetic properties of hydrogen-passivated armchair and zigzag GaN nanoribbons are investigated using density-functional theory. We explore that doped TM atom leads to additional levels in the band gap and thus plays an essential role in spin polarization and changes their properties. Depending on its location in the nanoribbon, the character of spin-dependent electronic property of a doped GaN-NR was analyzed. Our calculations show that, regardless of the position of Mn atoms, GaNNTs are stable in ferromagnetic phase.

Influence of fluorine molecule adsorption on the structural and electronic properties of armchair GaN nanoribbons

We have investigated how the structural and electronic properties of armchair GaN nanoribbons (AGaNNR) are affected under the influence of fluorine (F2) molecule adsorption. The adsorption was modeled considering different combinations of adsorption sites and orientations of the molecule. It was revealed that adsorption of F2-molecule over AGaNNR proceeds via exothermic process. The magnetic stabilization is also noticed which is greater than the thermal excitation energy and pledges magnetic properties for practical applications. The adsorption of F2 molecule causes a semiconductor to metallic transition in all the considered structures. The concentration effects were also investigated which revealed remarkable findings and may further lead to spintronic-device applications.

Ab Initio Investigations of Gallium Nitride Nanoribbons for Spin Filter and Negative Differential Behavior

This work demonstrates the influence of alternative edge passivation via H/F on the electronic and magnetic characteristics of gallium nitride nanoribbons (GaNNRs). For this study, the first-principles density functional theory (DFT) and non-equilibrium green function (NEGF) frameworks are deployed. Our study demonstrates that the selective edge passivation with F/H zigzag GaN nanoribbon (NR) is a strong contender for spintronics due to its half-metallic property under specific conditions. Various nano-configurations for the H/F ZGaNNRs passivation are investigated here. Thermodynamically, most stable configuration is alternate fluorinated F-GaN-F NR. Further, the negative differential resistance (NDR) behavior is also reported along with the perfect spin-filtering properties. This study paves the way to employ these 2-D nanostructures-based devices for spin filters, spin logic switches, and steep switching nanoelectronic devices.

Strain-Engineering of Electronic and Magnetic Properties of Chemically Passivated Zigzag GaN Nanoribbons: An Ab Initio Study

Strain-Engineering of Electronic and Magnetic Properties of Chemically Passivated Zigzag GaN Nanoribbons: An <i>Ab Initio</i> Study

First-principles predictions of tunable half metallicity in zigzag GaN nanoribbons with possible applications in CO detection and spintronics

Based on systematic first-principles density-functional theory simulations, we predict that the zigzag GaN nanoribbons (ZGaNNRs) can be used both as highly efficient CO detectors as well as spin filters. Our calculations, performed both on infinitely long nanoribbons, and also on finite strands, suggest that: (a) CO binds strongly at the edges of ZGaNNRs, and (b) that several of the resultant configurations exhibit half-metallic behavior. We considered various edge-passivation sites and found that all the resultant structures are thermodynamically stable. The metallic, half-metallic, and semiconducting configurations are observed as a function of CO passivation coverage. We also compute the current–voltage (I–V) characteristics of various structures using the Landauer formalism, and find that the devices made up of half-metallic configurations act as highly-efficient spin filters. The effect of CO concentration is also investigated which suggests a viable way to not just tune the electronic band gap of ZGaNNRs, but also their half metallicity. Our simulations thus suggest a new direction of research for possible device applications of III–V heterostructures.

Thermal transport properties of hexagonal monolayer group-III nitride nanoribbons

In this study, the thermal transport properties of hexagonal monolayer BN, AlN, and GaN nanoribbons are systematically investigated using non-equilibrium molecular dynamics simulations. Firstly, the effect of length, width, and temperature on the lattice thermal conductivities of these ribbons are explored. It is observed that increases in sample geometry lengths of simulations and decreases in temperature lead to an increase in the thermal conductivity of all three materials. Secondly, thermal rectification coefficients of ribbons are calculated by creating asymmetric thermal contacts through non-equilibrium molecular dynamics simulations. Thus, it is shown that thermal rectification factors of up to 20% can be achieved by manipulating the thermal asymmetry ratio in pristine structures without asymmetry of group-III nitride nanoribbons. These results imply that group-III nitride nanoribbons may be considered as an alternative option to control the heat flow in thermal management and thermoelectric device applications.

First Principle Investigations on Gas Molecules (CO₂, CO, NO₂, No and O₂) Using Armchair GaN Nanoribbons for Nano Sensor Applications

The paper presents the structural stability and electronic properties of various gas molecules AGaNNR with a width (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) of 5, 7 and 9. Width dependency is analysed using density functional theory (DFT). The electronic properties of all bare AGaNNR configurations exhibit the semiconducting nature. The reduction in the band gap has been noticed for selective edge adsorption. Due to interactions between CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , CO, NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , NO and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas molecules, AGaNNR turns its nature from semiconducting to metallic. Based on binding energy/adsorption calculations, O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -AGaNNR configuration found to be the most stable and energetically favoured configuration as compared to other configurations. CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , CO, NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , NO and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gases are selected as the targeted gas molecules and their adsorption on AGaNNRs have been selected for different configurations. The sensing capabilities of various harmful environmental gases are investigated and compared with width dependency. The selectivity of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> of AGaNNR configuration is the most preferred one amongst all considered configurations. Due to the lower recovery time, CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -AGaNNR configuration can be considered for fast sensing devices. The proposed device shows the potential for futuristic low power and high speed nano-scale sensor device applications.

DFT Investigation on Targeted Gas Molecules Based on Zigzag GaN Nanoribbons for Nano Sensors

In the present investigation, we studied the structural stability and electronic properties of bare and various adsorbed gas molecules ZGaNNR-2, ZGaNNR-4 and ZGaNNR-6 configurations. The electronic properties of all considered ZGaNNR configurations exhibit the metallic behaviour and it is verified through their band structures and densities of states. Based on binding energy/adsorption calculations, Bare-ZGaNNR-6 and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZGaNNR-6 configurations found the most thermostatic stable and energetically favoured configurations among all other considered ZGaNNRs. In transmission spectra, many distinct conductive states are observed in case of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZGaNNR-6. The selectivity of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZGaNNR has emerged as the most preferred (24.6) one among all considered configurations. CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZGaNNR-6 is emerged as the fast sensing device due to the lower recovery time (0.14 sec). The proposed device proves the high sensing capability towards the nano-scale devices.

First-principle investigations of cove edged GaN nanoribbon for nanoscale resonant tunneling applications

This work investigates the impact of cove edges in gallium nitride nanoribbons (GaNNRs) as cove edges nanoribbons are energetically more stable and facilitates further tunability of electronic properties of nanoribbons. Here structural, electronic, and transport properties of cove edged GaNNRs with hydrogen (H) passivation are investigated. For this investigation, the framework of non-equilibrium Green function (NEGF) formalism based on density functional theory (DFT) has been deployed. The effect of cove edge at nitrogen (N), gallium (Ga), and at both the edges for its potential ultra-scaled device applications are studied. As compared to the pristine semiconducting nature of H–GaN–H, present DFT-based calculations of cove edged GaNNRs exhibit a metallic nature via selective H-passivation. A comparative study of binding energy (Eb) revealed that the C–GaN–H nanoribbon is structurally more stable irrespective of the width in all considered cove edged GaNNRs. Interestingly, the proposed two-terminal cove edged GaNNRs devices exhibit negative differential resistance (NDR) effect based on selective edge passivation with hydrogen atoms. The observed NDR behavior suggests that cove edged GaNNRs with selective H-passivated GaNNRs have immense potential applications for preparing nanoscale NDR devices.

Fe-functionalized zigzag GaN nanoribbon for nanoscale spintronic/interconnect applications

The paper investigated the Zigzag GaN nanoribbons (ZGaNNR) using the density functional theory(DFT) and non equilibrium Green’s function(NEGF) framework. We have calculated the structural, electronic and transport properties of various Fe-ZGaNNR configurations. Based on the binding energy( $$E_{B}$$ ) calculations, Fe-doped@Ga_edge ZGaNNR(-6.51eV) is observed to be most structurally stable among different configurations. Our findings show the substitutional Fe passivation provides a stable bonding as compared to pristine configuration. The magnetic moment of different configurations depends upon the position of Fe atom. The discontinuity is observed in degenerative states of spin modes and same is follows by their respective density of states(DOS) and projected density of states(PDOS). Fe-termination@N_edge ZGaNNR is found to be a strong candidate for magnetic stabilization. High metallicity is observed in Fe-termination@both_the_edges ZGaNNR configuration. Further same is verified through current-voltage characteristics as current follow the pure linear behaviour. The practical application of the work on ZGaNNR can serve as a potential candidate for future low bias nanoscale spitronic devices and low power high speed interconnect applications.

Electronic structures and transport properties of low-dimensional GaN nanoderivatives: A first-principles study

Low-dimensional gallium nitride (GaN) nanoderivatives have recently attracted great attention, and they are one of the most attractive fields for future development of microelectronic devices. Here, the electronic structures and transport properties of GaN nanoderivatives were investigated by density functional theory. For two-dimensional bilayer GaN nanosheets, we found that AA-NN(GaGa) is the most stable structure among the five GaN stacking structures, and the stacking arrangement does not change the wide and indirect band gap of these two-dimensional bilayer stacked nanosheets. The transport properties of one-dimensional GaN nanoribbons were also investigated. The current in the bilayer GaN nanodevices was about twice that in the monolayer GaN nanodevices regardless of the nanoribbon morphology. That is, the bilayer GaN nanodevices show the current superposition law, like a parallel circuit, compared with their respective monolayer GaN model devices. The one-dimensional armchair boundary GaN nanoribbon devices showed the width effect because the width had a great effect on the current–voltage (I-V) curve and transport characteristics, but the one-dimensional zigzag boundary GaN nanoribbon devices did not and the I-V characteristic curves for different nanoribbon widths were similar. These extraordinary electronic structures indicate that GaN is promising for application in microelectronic devices.

Modulating Electronic Structures of Armchair GaN Nanoribbons by Chemical Functionalization under an Electric Field Effect.

The electronic and magnetic properties of oxygen- and sulfur-passivated one-dimensional armchair GaN nanoribbons (A-GaNNRs) are revealed using both first-principles density-functional theory and ab initio molecular dynamics simulations. We explore that an applied external electric field can further modulate the electronic properties of both pristine and passivated A-GaNNRs, thus changing their properties (semiconducting–metallic–half-metallic). A-GaNNRs of 0.9–3.1 nm width are subjected to further investigations, which reveal that sulfur termination transforms pristine A-GaNNRs from direct into indirect band gap semiconductors, without affecting their nonmagnetic nature. On the other hand, oxygen passivation introduces spin-polarized behavior with a finite magnetic moment. Magnetism characteristics in both bare and sulfur-passivated A-GaNNRs are induced by applying a critical electric field along the direction of NR width. The passivated A-GaNNRs are more stable compared to bare ones, while sulfur-passivated A-GaNNRs exhibit higher stability at higher temperatures (>500 °C). Thus, our results suggest that A-GaNNRs can be used in a broad range of electronic, optoelectronic, and spintronic applications.

First-principles study of sensing SO2 adsorption on III–V nitride nanoribbons

The design of efficient, low dimensional sensors is an active topic of research and development. Here, we study the adsorption of SO2 molecules on the edges of III–V nitride nanoribbons to explore their sensing potentials. Zigzag nanoribbons (ZXNNR) and armchair nanoribbons (AXNNR), X = B,Al,Ga, have been investigated. It was noticed that the adsorption of SO2 is mediated via formation of chemical bonds. The calculated adsorption energy varies from -1.09 eV to -4.89 eV for ZXNNR and -0.42 eV to -4.61 eV for AXNNR which ensures the structural stability of considered configurations against thermal excitations. Moreover, for all ZXNNR, a semiconducting to metallic transition has been observed whereas the band gaps in AXNNR are subjected to the adsorption configuration. Further, the selectivity of SO2 with all considered configurations with respect to O2 and N2 is also studied. It is revealed that the selectivity of SO2 with respect to N2 is more suitable as compared to O2. The analysis of recovery time indicates an excellent reversible characteristics in BN nanoribbons irrespective of their edge geometries. GaN nanoribbons could be reversible only for zigzag edges whereas unusually long recovery time in AlN nanoribbons presents them as a disposable sensing material. Present analysis portrays a detailed comparison of zigzag and armchair III–V nanoribbons towards their potential for designing futuristic nano-sensor devices.

Modulation of electronic structure properties of C/B/Al-doped armchair GaN nanoribbons

ABSTRACTThe electronic structures of C/B/Al-doped armchair GaN nanoribbons (aGaNNRs) are systematically studied by using density functional theory. We find that the original aGaNNRs are direct band gap semiconductors and that the gaps monotonically decrease with increasing widths. Interestingly, the B- or Al-doped aGaNNRs are also direct-band gap semiconductors with a slightly larger gap than their undoped aGaNNRs, while the C-doped aGaNNRs display metallic characteristics with an impurity state across the Fermi level in band structures. The semiconducting or metallic behaviours of C/B/Al-doped aGaNNRs can be explained by the orbital coupling between the extrinsic atom and primary Ga, N in their partial density of states. Our results show a useful way to modulate the band gaps of aGaNNRs.Using the density-functional theory, we performed a theoretical research to study the electronic structures of C/B/Al-doped armchair gallium nitride nanoribbons. The calculated band structures show that the perfect and original aGaNNRs are direct semiconductors regardless of ribbon widths, and gaps monotonically decrease with increasing the widths. The B/Al-doped aGaNNRs are semiconductors with a slightly larger gap, while metallic behavior presents in C-doped aGaNNRs with an impurity band across the EF. The results show a useful way to modulate the band gaps of aGaNNRs.

High-performance spin rectification in gallium nitride-based molecular junctions with asymmetric edge passivation

The spin transport properties of molecular devices constructed from zigzag gallium nitride nanoribbons (ZGaNNRs) are investigated by applying the non-equilibrium Green’s function formalism in combination with density functional theory. The computational results indicate that ZGaNNR systems show spin rectification with a high efficiency, approaching nearly 109, giant magnetoresistance with a ratio up to 108, perfect spin-filtering, and negative differential resistance effects. Importantly, our results reveal that intrinsic rectification can be observed regardless of their width. The microscopic origins of the rectification are revealed and discussed in terms of a spin-resolved transmission spectrum, the band structures of the ZGaNNRs, and the molecular projected self-consistent Hamiltonian. Our findings could be useful for designing GaN-based spintronic nanodevices.

Modulating the properties of multi-functional molecular devices consisting of zigzag gallium nitride nanoribbons by different magnetic orderings: a first-principles study.

Using the non-equilibrium Green's function formalism in combination with density functional theory, we calculated the spin-dependent electronic properties of molecular devices consisting of pristine and hydrogen-terminated zigzag gallium nitride nanoribbons (ZGaNNRs). Computational results show that the proposed ZGaNNR models display multiple functions with perfect spin filtering, rectification, and a spin negative differential resistance (sNDR) effect. Spin-dependent transport properties, spin density and transmission pathways with applied bias values were calculated to understand the spin filter and the sNDR effect. The spin filtering efficiency can be up to -100% or 100% within a large range of biases, and a dual spin filtering effect can also be found in these model devices. The highest rectification ratio reaches 4.9 × 109 in spin-down current of ZGaNNRs with only the passivated nitrogen edge, and only ZGaNNRs with the passivated gallium edge exhibit an obvious sNDR behavior with the largest peak to valley current ratio of 1.25 × 107. The proposed hydrogenated ZGaNNRs can be preferred materials for realizing oscillators, memory circuits and fast switching applications.

Electronic and magnetic properties of zigzag GaN nanoribbons with hydrogenation and fluorination

First principles calculations are performed to investigate the electronic and magnetic properties of hydrogenated and fluorinated zigzag GaN nanoribbons (zGaNNRs). Five kinds of possible different hydrogenated structures and four kinds of possible fluorinated structures are considered, and they show various electronic and magnetic properties. We find that the Ga-edges with two hydrogen atoms terminated or two fluorine atoms terminated are ferromagnetic while the N-edges with two hydrogen atoms terminated or two fluorine atoms terminated are nonmagnetic. Results show the structure is half-metal when the Ga-edges are saturated with two fluorine atoms and N-edges saturated with one fluorine atom. The Gibbs free energy of all the considered structures are calculated here to analyze the stability and their relation with chemical potentials. Moreover, the magnetic and electronic properties can be tailored by external electric field. zGaNNRs transform from half-metal to semiconductor under Ga→N direction electric field; it also can change from half-metal to magnetic metal then to nonmagnetic metal under N→Ga direction electric field.

Realizing Negative Differential Resistance/Switching Phenomena in Zigzag GaN Nanoribbons by Edge Fluorination: A DFT Investigation

AbstractGallium nitride (GaN) is a commonly used material for the high power electronic devices. Its 2D analog (layered GaN) can be a promising material in low power applications due to its flexible bandgap. This study investigates the structural stability, electronic and transport properties of zigzag edged GaN nanoribbons (ZGaNNRs), considering various edge passivations to gauge its potential for beyond silicon electronic devices. Present density functional theory based calculations reveal that metallic/semiconducting nature can be obtained in ZGaNNRs via controlled edge fluorination. Interestingly, F passivated ZGaNNRs are found to be most stable, making them preferable for practical applications. The proposed two terminal device exhibits a negative differential resistance behavior/switching characteristic with sufficiently large peak to valley current ratio/threshold voltage on the order of 102–1014/2.8–3.6 V which is a function of selective edge passivation. Present results can find practical applications in oscillators, memory circuits, and fast switching devices.

Electronic edge-state and space-charge phenomena in long GaN nanowires and nanoribbons

We studied space-charge-distribution phenomena in planar GaN nanowires and nanoribbons (NRs). The results obtained at low voltages demonstrate that the electron concentration changes not only at the edges of the NR, but also in the middle part of the NR. The effect is stronger with decreasing NR width. Moreover, the spatial separation of the positive and negative charges results in electric-field patterns outside the NR. This remarkable feature of electrostatic fields outside the NR may be even stronger in 2D material structures. For larger voltages the space-charge-limited current (SCLC) effect determines the main mechanism of transport in the NR samples. The onset of the SCLC effect clearly correlates with the NR width. The results are confirmed by noise spectroscopy studies of the NR transport. We found that the noise increases with decreasing NR width and the shape of the spectra changes with voltage increase with a tendency toward slope (3/2), reflecting diffusion processes due to the SCLC effect. At higher voltages noise decreases as a result of changes in the scattering mechanisms. We suggest that the features of the electric current and noise found in the NRs are of general character and will have an impact on the development of NR-based devices.

Ferromagnetism in zigzag GaN nanoribbons with tunable half-metallic gap

Using first-principles calculations, we investigate the electronic and magnetic properties of pristine and hydrogen-terminated zigzag GaN nanoribbons (ZGaNNRs). When the nitrogen edge of the ZGaNNRs is passivated, regardless of the gallium edge, the ZGaNNRs are wide band-gap semiconductors. However, when the nitrogen edge is unpassivated, the ZGaNNRs have 100% spin polarization around the Fermi level and become half metals. It is the strong interaction between the N-2p orbitals and Ga-4p orbitals that leads to the half-metallic ferromagnetism. What’s more, with the ribbons width increases, the half-metallic gap of only gallium edge hydrogenated ZGaNNRs decreases monotonously in a wide range. The tunability of half-metallic gap for ZGaNNRs can be applied to electronic and spintronic devices with wide or specific energy gaps.