Long room-temperature electron spin lifetimes in highly doped cubic GaN

Buß, J. H.; Rudolph, J.; Schupp, T.; As, D. J.; Lischka, K.; Hägele, D.

doi:10.1063/1.3478838

Cited by 22 publications

(18 citation statements)

References 23 publications

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“…Sample details are given in Ref. (). The cubic GaN is higly n‐doped with Si to a carrier concentration

n_{D} = 1 \times 10^{19}

cm −3 .…”

Section: Spin Dynamics In Bulk Cubic Ganmentioning

confidence: 99%

“…for cubic GaN by averaging over an isotropic angular distribution of

bold k

and replacing the absolute value k by the Fermi wavevector

k_{F}^{2} = false(3 π^{2})^{2 / 3} n_{D}^{2 / 3}

. A spin relaxation rate

γ_{italiczz, normalzb}^{D} = \frac{96 π^{4} γ_{normale, zb}^{2}}{35 ℏ^{2}} n_{D}^{2} τ_{p}

follows . This spin relaxation rate shows only a very weak temperature dependence due to the weak temperature dependence of both

n_{D}

and

τ_{p}

().…”

Section: Spin Dynamics In Bulk Cubic Ganmentioning

confidence: 99%

“…While the spin dynamics in the dilute nitrides GaNAs and GaInNAs , and of holes () and especially excitons in GaN has been intensively studied, the electron spin dynamics in GaN had been only rarely studied after the early work of Beschoten (). Here, we will give a review of our experimental investigations of the electron spin dynamics in bulk GaN by time‐resolved magneto‐optical Kerr‐rotation (TRKR) spectroscopy . After a short overview of the theory of electron spin relaxation in GaN, we will first discuss the spin dynamics in bulk wurtzite GaN in dependence on external magnetic field, temperature, and doping density.…”

Section: Introductionmentioning

confidence: 99%

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Electron spin dynamics in GaN

Rudolph

Buß

Hägele

2014

Physica Status Solidi (b)

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This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Gallium nitride is a promising material system for spintronics, offering long spin relaxation times and prospects for room-temperature ferromagnetism. We review the electron spin dynamics in bulk GaN. Time-resolved magneto-optical studies of both the wurtzite and the cubic phase of GaN show the dominance of Dyakonov-Perel (DP) relaxation for free conduction band electrons. Spin relaxation in the wurtzite phase is characterized by an intrinsic spin relaxation anisotropy and the limitation of spin lifetimes by a strong Rashba term. Spin lifetimes are strongly enhanced in cubic GaN, where only a weak Dresselhaus term contributes to DP relaxation. Ion-implanted wurtzite GaN shows a strong increase of electron spin lifetimes for increasing implantation dose, caused by increasing localization of carriers. The spin dynamics of conduction band electrons in Gd-implanted GaN as a candidate for a room-temperature ferromagnetic semiconductor is also only governed by localization effects and does not show signs of an efficient exchange coupling between the electrons and the magnetic Gd ions.1 Introduction Spintronics as the novel spin-based semiconductor electronics has been an intense and fruitful field of research in the last years, leading to the discovery and detailed understanding of numerous spin effects [1][2][3][4][5]. In addition, a plethora of possible applications including, e.g., the famous spin transistor [6] or spin optoelectronic devices [7][8][9], has been proposed. However, for the realization of the proposed concepts challenging requirements are imposed on the underlying semiconductor materials, like, e.g., very long spin lifetimes or ferromagnetic behavior with Curie temperatures above room temperature. These challenges have triggered intense research on optimized structures and new materials. In particular, GaN has attracted strong interest as it promises to combine fascinating properties, ranging from weak spin-orbit coupling due to its light constituting elements over high-temperature ferromagnetism upon doping with rare earth ions [10] up to its good optoelectronic properties [11] and its well established use in the semiconductor industry [12]. In addition, GaN is a highly instructive model system for the influence of crystal symmetry on the electron spin dynamics as besides the thermodynamically stable wurtzite phase also the metastable cubic phase can be prepared [13]. While the spin dynamics in the dilute nitrides GaNAs and GaInNAs [14][15][16][17][18], and of holes [19] and especially excitons in GaN [20][21][22][23]

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“…Sample details are given in Ref. (). The cubic GaN is higly n‐doped with Si to a carrier concentration

n_{D} = 1 \times 10^{19}

cm −3 .…”

Section: Spin Dynamics In Bulk Cubic Ganmentioning

confidence: 99%

“…for cubic GaN by averaging over an isotropic angular distribution of

bold k

and replacing the absolute value k by the Fermi wavevector

k_{F}^{2} = false(3 π^{2})^{2 / 3} n_{D}^{2 / 3}

. A spin relaxation rate

γ_{italiczz, normalzb}^{D} = \frac{96 π^{4} γ_{normale, zb}^{2}}{35 ℏ^{2}} n_{D}^{2} τ_{p}

follows . This spin relaxation rate shows only a very weak temperature dependence due to the weak temperature dependence of both

n_{D}

and

τ_{p}

().…”

Section: Spin Dynamics In Bulk Cubic Ganmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Electron spin dynamics in GaN

Rudolph

Buß

Hägele

2014

Physica Status Solidi (b)

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“…This yields the loss of the electron spin memory in a few tens or hundreds of picoseconds [11,12]. As the driving force in the DP spin relaxation is the SO splitting, its reduction is expected to lead to an increase of the spin relaxation time [13,14]. In bulk zinc blende semiconductor, the Bulk Inversion Asymmetry (BIA) spin splitting, also called Dresselhaus term, is determined by [1,8]:…”

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confidence: 99%

Full Electrical Control of the Electron Spin Relaxation in GaAs Quantum Wells

et al. 2011

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The electron spin dynamics in (111)-oriented GaAs/AlGaAs quantum wells is studied by timeresolved photoluminescence spectroscopy. By applying an external field of 50 kV/cm a two-order of magnitude increase of the spin relaxation time can be observed reaching values larger than 30 ns; this is a consequence of the electric field tuning of the spin-orbit conduction band splitting which can almost vanish when the Rashba term compensates exactly the Dresselhaus one. The measurements under transverse magnetic field demonstrate that the electron spin relaxation time for the three space directions can be tuned simultaneously with the applied electric field.The control of the electron spins in semiconductors for potential use in transport devices or quantum information applications has attracted a great attention in recent years [1][2][3]. In 2D nanostructures made of III-V or II-VI semiconductors, the dominant loss of electron spin memory is related to the spin relaxation mechanism known under the name Dyakonov-Perel (DP) [4,5]. In these materials, the absence of inversion symmetry and the spin-orbit (SO) coupling are responsible for the lifting of degeneracy for spin | 1/2 and | −1/2 electrons states in the conduction band (CB). This splitting plays a crucial role for the spin manipulation and spin transport phenomena [6,7]. As it depends strongly on the crystal and nanostructure symmetry [8][9][10], it can be efficiently tailored as explained below. The SO splitting can be viewed as the result of the action on the electron spin of an effective magnetic field whose amplitude and direction depend on the wave vector k of the electron. The electronic spin will precess around this field with an effective, momentum dependent, Larmor vector Ω whose magnitude corresponds to the CB spin splitting. This effective magnetic field changes with time since the direction of electron momentum varies due to electron collisions. As a consequence, spin precession around this field in the intervals between collisions gives rise to spin relaxation. In the usual case of frequent collisions, the relaxation time of an electron spin oriented along the direction i can be written [4]:where Ω 2 ⊥ is the mean square precession vector in the plane perpendicular to the direction i (i=x, y, z) and τ * p the electron momentum relaxation time. This yields the loss of the electron spin memory in a few tens or hundreds of picoseconds [11,12]. As the driving force in the DP spin relaxation is the SO splitting, its reduction is expected to lead to an increase of the spin relaxation time [13,14]. In bulk zinc blende semiconductor, the Bulk Inversion Asymmetry (BIA) spin splitting, also called Dresselhaus term, is determined by [1,8]:where γ is the Dresselhaus coefficient and k = (k x , k y , k z ) the electron wavector. In a quantum well (QW) where the momentum component along the growth axis z is quantized, the vector Ω due to the BIA for the lowest electron sub-band writes:where k 2 z is the averaged squared wavevector along the growth direction and k the...

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“…13 However, for the spin dynamics under the influence of high electric field 14 or with spin pumping by high-energy laser, 15 electrons can be driven into the high valleys.…”

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confidence: 99%

Spin–orbit coupling and -factor of -valley in cubic GaN

Shen

2011

Solid State Communications

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We report our theoretically investigation on the spin-orbit coupling and g-factor of the X-valley in cubic GaN. We find that the spin-orbit coupling coefficient from sp 3 d 5 s * tight-binding model is 0.029 eV·Å, which is comparable with that in cubic GaAs. By employing the k · p theory, we find that the g-factor in this case is only slightly different from the free electron g-factor. These results are expected to be important for the on-going study on spin dynamics far away from equilibrium in cubic GaN.PACS numbers: 71.70. Ej, 61.82.Fk Due to the existence of the wide energy gap between the conduction band and the valence band, GaN has been proposed to be a promising candidate for many electronic applications, such as the solid-state ultraviolet optical sources and high-power electronic devices.

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Long room-temperature electron spin lifetimes in highly doped cubic GaN

Cited by 22 publications

References 23 publications

Electron spin dynamics in GaN

Electron spin dynamics in GaN

Full Electrical Control of the Electron Spin Relaxation in GaAs Quantum Wells

Spin–orbit coupling and -factor of -valley in cubic GaN

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