Spin relaxation inGaAs/Alx

Abstract

Spin dynamics of photoexcited carriers in GaAs/Al x Ga 1Ϫx As quantum wells have been investigated in a wafer containing twelve different single quantum wells, allowing full investigation of well-width and temperature dependences with minimal accidental variations due to growth conditions. The behavior at low temperatures is dominated by excitonic effects, confirming results described in detail by others. Between 50 and 90 K there is a transition from excitonic to free-carrier-dominated behavior; both the temperature and time scale of the transition are in excellent agreement with a theoretical model for exciton dissociation. Above 90 K we find two-component spin decays consisting of an unresolved component ͑faster than 2 ps͒ associated with exciton dissociation and hole spin-relaxation and a longer-lived component that yields the electron spin-relaxation time. In the free-carrier regime, the electron spin-relaxation rate in wide wells follows that for bulk GaAs, which varies approximately as T 2 . For narrow wells the rate is approximately independent of temperature and varies quadratically with confinement energy. This behavior is consistent with dominance of the D'yakonov-Perel mechanism of electron-spin relaxation and the expected behavior of the electron mobility. The data show evidence of the influence of electron scattering by interface roughness.

Spintronics: Fundamentals and applications

“…At low T, in addition to the Bir-AronovPikus mechanism, s will deviate from that in the bulk due to impurity scattering. The Bir-Aronov-Pikus and Elliot-Yafet mechanisms were found not to be relevant to the observed data (Malinowski et al, 2000). Figure 21 shows the dependence of 1/ s on the experimentally determined confinement energy E 1 for a variety of quantum wells on the same wafer (Malinowski et al, 2000).…”

“…Figure 20 plots the temperature dependence of 1/ s in the interval 90ϽTϽ300 K for quantum wells of widths L ranging from 6 to 20 nm (Malinowski et al, 2000). The wells, with xϭ0.35 and orientation along [001], were grown on a single wafer to minimize sample-to-sample variations when comparing different wells.…”

“…Spin relaxation was attributed to Bychkov-Rashba spin splitting in these asymmetric wells, estimating the corresponding ប␣ BR in Eq. (88) to be around 1ϫ10 Ϫ14 eV m (Wilamowski and 84 Here is a list of selected references with useful data on s in GaAs/AlGaAs quantum wells: confinement energy dependence has been studied by Tackeuchi et al (1996); Britton et al (1998) ;Ohno, Terauchi, et al (1999; Endo et al (2000); Malinowski et al (2000); temperature dependence is treated by Wagner et al (1993); Ohno, Terauchi, et al (1999; Malinowski et al (2000); Adachi et al (2001); carrier concentration dependence is studied by Sandhu et al (2001); dependence on mobility is examined by Ohno, Terauchi, et al (1999); and dependence on magnetic field is studied by Zhitomirskii et al (1993). .…”

Effect of symmetry reduction on the spin dynamics of (001)-oriented GaAs quantum wells

“…The dominant spin relaxation mechanism in (001) grown GaAs/AlGaAs quantum wells is the Dyakonov-Perel (DP) spin-dephasing mechanism. 17 The electron experiences a momentum dependent effective magnetic field about which the electron spin precesses. Momentum relaxation occurs due to scattering from ionized impurities.…”

Spin Extraction Theory and Its Relevance to Spintronics

“…It is assumed that spin relaxation time in the well is faster than the escape time (n i;s ' n i =2). The spin relaxation time in the well is around tens of ps [10], whereas the escape rate is 1 ns [11]. Spin relaxation in the well does not cancel the spin polarization in the bulk region.…”