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The deriving method of spin–orbit (SO) parameters using a single-frequency analysis was examined in a transient regime of diffusive spin dynamics in InGaAs/InAlAs multiple quantum wells. Transient regime of diffusive spin dynamics is the time regime when the spin precession frequency induced by SO magnetic fields decreases and changes with time. Recently, we have established a method of deriving SO parameters by scanning time-resolved Kerr rotation microscopy in this transient regime [Kawaguchi et al., Appl. Phys. Lett. 115, 172406 (2019)] using the time-dependent spin precession frequency analysis. Although reliable SO parameters were derived, time-independent single-frequency analysis is still attractive because of its simplicity. In this paper, SO parameters' derivation was performed by the single-frequency analysis comparing the experiment and the Monte Carlo (MC) simulation. The best fit of the simulation to the measurement for the SO-induced frequency yields the derivation of SO parameters; however, the derived values were different from the reliable SO parameters derived by the time-dependent analysis. This discrepancy arises from a spin relaxation time difference between the experiment and MC simulation. After intentionally adjusting the spin relaxation time of the MC simulation to the experiment, the SO-induced frequency obtained by the MC simulation with reliable SO parameters reproduced the experiment well. We found that the spin relaxation time adjustment of the MC simulation to the experiment is necessary to obtain accurate SO parameters from the single-frequency analysis comparing the experiment with the MC simulation. [ABSTRACT FROM AUTHOR]

Spatial and temporal diffusive spin dynamics in the transient regime for 10-nm-wide InGaAs/InAlAs quantum wells were investigated using time-resolved optical Kerr rotation (TRKR) microscopy. The transient regime of diffusive spin dynamics is a specific regime which appears after local excitation but before the formation of a spin mode. In this regime, the spin precession frequency induced by the spin–orbit (SO) magnetic field decreases with time since the diffusive velocity decreases as the distribution of spins expands. In this study, by decreasing the spot size of the excitation pulse, we examined the spin dynamics in the transient regime. We carefully analyzed the TRKR signals using time-dependent frequency equations established by Kohda et al. [Appl. Phys. Lett. 107, 172402 (2015)]. All the TRKR signals could be well reproduced by the time-dependent frequency equations. Our analysis reveals that the spin precession frequencies arising from the SO interaction gradually decrease with time, and they allowed the extraction of the Rashba and Dresselhaus SO parameters. We revealed that SO parameters can be extracted accurately via scanning measurements in the diffusive motion of local spin excitation even in the time periods before the appearance of the spin mode. [ABSTRACT FROM AUTHOR]

We investigated flatness of growth-interrupted InAlAs and InGaAs surfaces using In0.53Ga0.47As/In0.52Al0.48As quantum wells (QWs) with well widths (Lw) of 0.6–12 nm grown on a (4 1 1)A-oriented InP substrate by molecular beam epitaxy. In the (4 1 1)A QWs with growth interruption (GI) at the InGaAs/InAlAs interface (InAlAs surface), full width at half maximum (FWHM) of a photoluminescence peak of the 1.2-nm-thick InGaAs well was as narrow as 15.6 meV, which was almost the same as that of the corresponding well without GI (14.4 meV). On the other hand, the FWHM of the (1 0 0) QWs with GI at the InAlAs surface was 24.1 meV (Lw=1.2 nm), which was 55% larger than that of the (4 1 1)A QWs with GI at the InAlAs surface. This result indicates that the effectively atomically flat interfaces [(4 1 1)A super-flat interfaces] are successfully kept in spite of introducing GI, while GI makes the (1 0 0) interface much rough. [Copyright &y& Elsevier]

Single-particle relaxation times in In0.7Ga0.3As/In0.52Al0.48As quantum well high electron mobility transistor (QW-HEMT) structures for two subbands (i=0 and 1) are studied by fast Fourier transform analysis of Shubnikoov-de Haas (SdH) oscillations measured at 4 K in order to investigate remote impurity (RI) scattering in the QW-HEMT structure with effectively atomically flat interfaces over a wafer-size area ((4 1 1)A super-flat interfaces) grown on a (4 1 1)A InP substrate by molecular beam epitaxy. The (4 1 1)A QW-HEMT structure with thin spacer thickness of 3 nm shows two times longer single-particle relaxation times (τs(0)=0.71×10−13 s and τs(1)=1.08×10−13 s) compared to those (τs(0)=0.37×10−13 s and τs(1)=0.49×10−13 s) for the corresponding QW-HEMT structure with conventional (1 0 0) interfaces, indicating that RI scattering is much reduced in the (4 1 1)A sample. Calculations of τs(0) limited by RI scattering assuming random distribution of sheet-doped impurities show that the enhancement of τs(0) for the (4 1 1)A QW-HEMT structure cannot be explained by laterally uniform spacer thickness resulting from the (4 1 1)A super-flat interfaces. Much reduced RI scattering in the (4 1 1)A QW-HEMT structure is considered to be mainly caused by extremely uniform distribution of sheet-doped impurities. [Copyright &y& Elsevier]