Experimental determination of Rashba spin-orbit coupling in wurtziten-GaN:Si

Abstract

Millikelvin magnetotransport studies are carried out on heavily n-doped wurtzite GaN:Si films grown on semi-insulating GaN:Mn buffer layers by metal-organic vapor phase epitaxy. The dependence of the conductivity on magnetic field and temperature is interpreted in terms of theories that take into account disorder-induced quantum interference of one-electron and many-electron self-crossing trajectories. The Rashba parameter α R = (4.5 ± 1) meVÅ is determined, and it is shown that in the previous studies of electrons adjacent to GaN/(Al,Ga)N interfaces, bulk inversion asymmetry was dominant over structural inversion asymmetry. The comparison of experimental and theoretical values of α R across a series of wurtzite semiconductors is presented as a test of current relativistic ab initio computation schemes. Low-temperature decoherence is discussed in terms of disorder-modified electron-electron scattering.

Controlling a three dimensional electron slab of graded AlxGa1−xN

“…According to the curves in Fig. 3 (a) Since all the samples discussed here have n c far above the Mott MIT limit, the graded Al 1−x Ga x N layers are expected to be in a weak localization regime [39]. This is confirmed by the observation of negative MR (positive magnetoconductance) in the magnetoresistance data acquired as a function of the applied magnetic field and for various temperatures 2 K≤T≤50 K, as reported in Fig.…”

“…However, for samples S3 and S4, grown on a degenerate GaN:Si reservoir with n c =(1.2×10 19 ) cm −3 , one can observe an enhanced carrier density, reaching (6×10 19 ) cm −3 for S3 and (1.4×10 20 ) cm −3 for S4. These values are greater than those observed for n-GaN:Si [39] and for 3DES in MBE g-Al x Ga 1−x N/GaN systems [19,36]. The difference between S3 and S4 resides solely in the thickness of the g-Al x Ga 1−x N layer.…”

“…The conductivity of the samples increases with increasing n c and this can be achieved either by augmenting the gradient range of the Al content while not varying the thickness of the graded layer, or by decreasing the layer thickness for a fixed range of the gradient, or by using a buffer/reservoir with a carrier concentration orders of magnitude higher than the one of u-GaN. The observed magnetoresistance points to quantum corrections to the conductivity, due to weak localization [39]. With the present work it is shown that controllable g-Al x Ga 1−x N leading to a 3DES can be fabricated in a MOVPE process.…”

Two-Probe Measurements of Electron Transport in GaN:Si/(Ga,Mn)N/GaN:Si Spin Filter Structures

“…4. A very weak negative magnetoresistance is measured in every case with the overall line-shape analogous to the one observed in similarly heavily Si doped GaN layers, which was well accounted for by the weak localization effect in semiconductors on the metallic side of the MIT [11]. However, on every MR(H) a symmetric maximum at around 1.5 kOe is seen.…”

“…• C and annealed at 1040 18 cm −3 [10] and it guarantees the semimetallic behaviour of these layers down to the lowest cryogenic temperatures [11]. The obtained samples are systematically characterized by atomic force microscope (AFM), high resolution X-ray diffraction (HRXRD), and high resolution transmission electron microscopy (HRTEM).…”