Effect of ionized impurity screening on spin decoherence at low and intermediate temperatures in GaAs

Abstract

We study the effect of charged impurity screening on spin decoherence in bulk n-type GaAs, and analyse in details the effect of the use of different Born approximations applied to a linearized Thomas-Fermi screening theory. The spin relaxation times are calculated by ensemble Monte Carlo techniques, including electron-electron, electron-impurities, and electron-phonons scattering. We carefully choose a parameter region so that all the physical approximations hold, and, in particular, a Yukawa-type potential can be used to describe the screened Coulomb interaction and the Born series converges. Our results show that including the second order Born approximation yields much shorter spin relaxation times compared to the commonly implemented first Born approximation: spin relaxation times may be reduced by hundreds of picoseconds, with the first Born approximation overestimating results by 30% or more for a large region of parameters. Though our ensemble Monte Carlo simulations include electron-electron and electron-phonon interactions, when considering low to intermediate carrier densities and T > 50 K, but T smaller than the Fermi temperature, our results are in good agreement with Dyakonov-Perel theory when this includes electron-impurity interactions only, which supports this to be the most relevant scattering mechanism for bulk GaAs in this low-intermediate temperature regime.

Inconsistency between linearized Thomas–Fermi approximation and electron-ionized impurity scattering rate in the first Born approximation

“…5 we expect that the B2 becomes important for much lower carrier energies than E F , that is, when the scattering probability, given by Eq. 12, becomes weakly dependent on the angle θ [5].…”

“…In the following we study wave vector transfer distribution for a doped GaAs with these band-structure parameters: ε = 12.9 ε 0 , m * = 0.067 m e , ε 0 , m e being the vacuum permittivity and the electron bare mass respectively [40]. The doping concentration is n i = 5 × 10 17 cm −3 , and we shall assume that the electron density n e = n i [5] which, ignoring the crystal lattice structure, corresponds to a homogeneous electron gas (jellium model) at T F 398 K with Wigner-Seitz radius r s = 0.7 (1/n e ≡ (4π/3) (r s a * 0 ) 3 , a * 0 being the effective Bohr radius). The latter condition guarantees that RPA holds.…”

“…In general ionized impurities affect the carrier dynamics in bulk semiconductors at high doping concentrations or at low temperatures, see Ref. [4,5].…”

“…Imperfections, vacancies and interstitials, can alter major physical properties of solids such as the phonon spectrum, as well as optical and electrical properties to some extent [1].Defects in semiconductors such as Si, Ge and compound semiconductors such as GaAs in general dissolve on lattice sites creating shallow point-like acceptors or donors, which make them suitable for electronic and spintronic device applications [2,3]. In general ionized impurities affect the carrier dynamics in bulk semiconductors at high doping concentrations or at low temperatures, see [4,5].Different theoretical approaches have been proposed to tackle the problem of interactions between point-like ionized impurities and electrons in solids. The standard tools are: the Green's function formalism [6], density functional theory (DFT) [7-9] and first order time-dependent perturbation theory of quantum mechanics [10].…”

“…Defects in semiconductors such as Si, Ge and compound semiconductors such as GaAs in general dissolve on lattice sites creating shallow point-like acceptors or donors, which make them suitable for electronic and spintronic device applications [2,3]. In general ionized impurities affect the carrier dynamics in bulk semiconductors at high doping concentrations or at low temperatures, see [4,5].…”