Geometry and diameter dependence of the electronic and physical properties of GaN nanowires from first principles

Abstract

We present a comprehensive first-principles investigation of the atomic and electronic structures of gallium nitride nanowires, and examine the dependence on nanowire diameter and shape. We consider nanowires in the [0001] growth direction, with diameters ranging from 8 to 35 Å, and investigate the influence of saturating the dangling bonds at the edges of nanowires. We find that unsaturated nanowires are semi-conducting and contain dangling bond states in the region of the band gap, the positions of which remain rather constant with varying diameter. Saturating the nanowires with hydrogen removes these states, and the band gap decreases with increasing nanowire diameter. For the unsaturated wires there is a considerable contraction of the Ga-N bondlengths at the edge of the wires of 6.0-7.4%, while for saturated wires it is <1.5%. We also calculate the heat of formation of the nanowires and find that as the diameter of the nanowire increases, the average relative stability of the nanowire increases, as intuitively expected.

Quantum confinement effects in gallium nitride nanostructures:ab initioinvestigations

“…We generate GaN nanodots using our previously reported wurtzite bulk GaN (a=3.18Å, c=5.18Å, u=0.377) structure. [23] Nanodots of varying sizes are generated, where we saturate the dangling bonds at the surface with appropriately chosen fractional charge hydrogen atoms (a charge of 0.75e or 1.25e, depending on whether the dangling bond is on a nitrogen or gallium atom, respectively). This ensures that effectively bulk-like GaN bonds are formed, as has been suggested for saturating dangling bonds of semiconductor compounds.…”

Bandgap engineering of GaN nanowires

“…The first principles was performed to study Hex-GaN NWs with diameters ranging 11 to 32 Å, found that n is 1.17. 30 Carter et al 14 reported the value of n for hexagonal wires form SIESTA is 1.17 and from DMOL 3 is 1.46. But the Tri-angular wires have a small value of n is 0.901 and 0.965 form SIESTA and DMOL.…”

“…3 shows, which is agreeable with previous study. 14 We further investigate the dependence of bandgap on transverse size with different cross sections. Fig.…”

“…13 Moreover, nanowires with different cross sectional shapes, including triangular and hexagonal have also been successfully prepared. [14][15][16] However, the impact of diameters and cross sectional geometries on electronic properties of GaN nanowires is still largely unknown.…”

Transition from positive to negative magnetoresistance induced by a constriction in semiconductor nanowire

“…1(a)], z 0 = 100 nm is the position of its center (measured with respect to the source, for which z = 0), the nanowire has length L = 200 nm, r 0 = 20 nm is the radius of the nanowire outside the constriction region, and r c is the radius of the nanowire in the middle of the constriction. Since for the values of r c less then ∼5 nm the band structure strongly depends on the geometric parameters of the nanosystems, 36,37 and thus the effective mass approximation is no longer valid, we limit our calculations to r c > 10 nm.…”