[Show abstract][Hide abstract] ABSTRACT: The magneotransport properties of a high carrier concentration and high mobility 20-nm thick In0.53Ga0.47As/In0.52Al0.48As quantum well (QW) are investigated by tilt angle dependent Shubnikov-de Haas oscillations and by weak antilocalization (WAL) in an in-plane magnetic field. The effective g-factor g* and zero field spin splitting Δ0 are extracted from tilt angle dependent beating pattern. We found that g* shows a dramatic reduction with increasing carrier density due to the increased effective band gap. Furthermore, an anomalously rapid suppression of the WAL effect with increasing in-plane magnetic field B|| is observed. This reveals that the total dephasing rate is not solely contributed by Zeeman splitting. The microroughness scattering in the QW is proposed to be another factor to cause the dephasing and thus responsible for this effect.
Journal of Applied Physics 01/2013; 113:033704. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of different scattering on two-dimensional electron gases (2DEGs) in lattice matched In0.53Ga0.47As/In0.52Al0.48As quantum wells with silicon δ-doped in one barrier layer have been investigated by means of magneto-transport measurements. For the studied samples, the 2DEGs have occupied two subbands. It is found that the dominant scattering mechanism is ionized impurities scattering for the two subbands’ electrons. Besides the dominant scattering mechanism of ionized impurities scattering, Coulomb scattering also plays a role in scattering mechanism for both subbands. Both the transport scattering time and the quantum scattering time of the second subband are larger than those of the first subband. It is because that the electrons of the first subband are, on average, closer to the ionized impurities in the doped layer, they will be scattered more strongly than those in the second subband. Due to the electron wave functions for the second subband spread more widely in the quantum wells, the alloy disorder scattering is more important for the carriers in the second subband than that in the first subband.
Journal of Applied Physics 07/2012; 112(2). · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have investigated spin-related oscillatory magnetoresistances of the two-dimensional electron gas in the inversion layer on bulk p-Hg1−xCdxTe at low temperatures. The oscillatory magnetoresistances are found to display beating pattern at low magnetic fields and to exhibit spin-splitting structure at high magnetic fields. We attribute the beating pattern to zero-field spin splitting due to spin-orbit coupling by analyzing fast-Fourier-transform results and Hall resistance. By modulating the oscillatory magnetoresistances we investigate the influence of spin-orbit coupling, Zeeman splitting, and the second populated subband on the appearance of beating patterns and the spin-splitting structure in oscillatory magnetoresistances. The strong spin-orbit coupling and the large effective g factor are demonstrated to be the significant parameters in controlling the appearance of spin-related oscillatory magnetoresistance in the inversion layer on bulk p-Hg1−xCdxTe. A good agreement between magnetoresistance data and theory suggests a spin-orbit coupling parameter α = 2.8 × 10−11 eV•m and the effective g factor g* = −44.0. The spin-orbit coupling effect presented in the inversion layer on bulk p-Hg1−xCdxTe provides a potential candidate for spintronic devices.
Journal of Applied Physics 06/2011; 109(11):113717-113717-6. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The results of an experimental study of quantum correction of electron–electron interaction (EEI) to the conductivity of two-dimensional electron gas (2DEG) in an undoped heterostructure are reported. A small but significant decrease of the Hall slope with the increase of temperature was discovered. This is not due to the increase of electron concentration as temperature increases but to the EEI effect. Both diffusion and ballistic contributions of EEI to the conductivity of 2DEG were observed. As the temperature increases, the negative diffusion EEI correction to the conductivity increases in an absolute value while the ballistic EEI correction reduces to a renormalization of the transport mobility.Highlights► The electron–electron interactions are studied by magneto-transport measurements. ► The Hall slope decreases with the increase of temperature. ► The ballistic EEI correction reduces to a renormalization of the mobility. ► The diffusion EEI correction increases in absolute value with the temperature.
Solid State Communications 06/2011; 151(12):879-882. · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effective masses for spin-up and spin-down electrons of a partially spin-polarized Fermi liquid are theoretically expected to be different. We extract the spin-up and spin-down effective masses from magnetotransport measurements at different temperatures for a two-dimensional electron gas in an In0.65Ga0.35As/In0.52Al0.48As quantum well exhibiting zero-field spin splitting. We apply two analytical methods, one involving the simultaneous fitting of fast Fourier transform (FFT) spectra and the other involving inverse FFT analysis. Both methods confirm that the effective masses for spin-up and spin-down are different, consistent with theoretical expectations.
Journal of Applied Physics 01/2011; 110. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the insulator-quantum Hall conductor transition in two high-density gated InGaAs/InAlAs quantum well samples. We observe a well-defined critical magnetic field and verify this marks a genuine phase transition by investigating the scaling behavior of the longitudinal resistivity with field and temperature at fixed electron density. Consistent with prevailing experimental results the critical field decreases with increasing electron density in one sample (QW0710). In the other sample (QW0715), with higher delta doping density, however, we unexpectedly find that the critical field increases with increasing electron density. This unexpected behavior may be the result of the system entering the classical percolation regime.
Journal of Applied Physics 09/2010; 108(6):063701-063701-6. · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The beating patterns in the Shubnikov-de Haas oscillatory
magnetoresistance originating from zero-field spin splitting of
two-dimensional electron gases (2DEGs) in
quantum wells with silicon δ doped on the upper barrier layer
have been investigated by means of magnetotransport measurements before
and after illumination. Contrary to the expectation, after each
illumination, the beating nodes induced by the zero-field spin-splitting
effect shift to lower and lower magnetic field due to the decrease in
the zero-field spin-splitting energy of the 2DEGs. The anomalous
phenomenon of the shift of the beating nodes and the decrease in
spin-orbit coupling constants after illumination cannot be explained by
utilizing the previous linear Rashba model. It is suggested that the
decrease in the zero-field spin-splitting energy and the spin-orbit
coupling constant arise from the nonlinear Rashba spin splitting.
[Show abstract][Hide abstract] ABSTRACT: We report on the strong spin-orbit (SO) interaction in a gated high-mobility In <sub>0.53</sub> Ga <sub>0.47</sub> As / InP quantum well two-dimensional electron gas. We establish that the SO interaction is dominated by the Rashba mechanism. The Rashba coupling parameters determined from analysis of both weak antilocalization and the beating pattern in the Shubnikov–de Haas oscillations are in reasonable agreement, and the small difference between them was explained by a magnetic-field-dependent effective g factor. The zero-field spin splitting shows nonmonotonic behavior with a maximum as the electron density is varied with the applied gate voltage. This is related to strong Rashba SO coupling in our sample.
Journal of Applied Physics 04/2010; · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the parabolic negative magnetoresistivity in a gated In0.53Ga0.47As/InP quantum well structure where the scattering potential is predominantly long range. This magnetoresistivity is caused by the electron–electron interactions and is fitted to estimate the interaction corrections to the Drude conductivity. These corrections are smaller than the prediction of a recent theory [I.V. Gornyi, A.D. Mirlin, Phys. Rev. Lett. 90 (2003) 076801], and can be quantitatively described by Altshuler’s theory.
Solid State Communications 02/2010; 150(s 5–6):251–253. · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the magnetotransport properties of a gated In <sub>0.53</sub> Ga <sub>0.47</sub> As / In P quantum well structure in the presence of spin splitting when only one electronic subband is occupied. We develop an analytical method to extract the quantum mobilities for the two spin subbands. Ionized impurity scattering and alloy disorder scattering are determined to be important in this system. Larger quantum mobility is found for the higher-energy spin subband. We also demonstrate that the difference between the quantum mobilities for the two spin subbands can be altered with the gate.
Journal of Applied Physics 11/2009; · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The quantum corrections to magnetoconductivity were studied in a
high-mobility InGaAs/InAlAs sample with strong spin-orbit coupling. The
weak antilocalization-induced drop in conductivity increases with
decreasing conductivity. The experiment is well explained by theory. A
spin-splitting energy larger than 5 meV obtained by fitting indicates
strong spin-orbit coupling. The extracted dephasing rate as a function
of temperature can be qualitatively described by modified Fermi-liquid
theory with small-energy-transfer processes. Nonetheless, the extracted
dephasing rate linearly increases with increasing conductivity, which is
in conflict with the Fermi-liquid model.
[Show abstract][Hide abstract] ABSTRACT: We report on the magnetotransport properties of 100 nm wide parabolic quantum wells and observe an enhancement of the Hall resistance in one sample but not the other. This phenomenon is likely related to the effective thickness of the electronic slab. We also observe a parabolic negative magnetoresistance originating from electron-electron interactions when only one subband is occupied in one of the samples. The interaction correction to the Drude conductivity is extracted using two methods. We find that the extracted interaction correction increases with increasing tilted angle, for which two possible explanations are given.
Journal of Applied Physics 02/2009; · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: (La0.5Sr0.5)CoO3 (LSCO) thin films have been fabricated on silicon substrate by the pulsed laser deposition method. The effects of substrate
temperature and post-annealing condition on the structural and electrical properties are investigated. The samples grown above
650°C are fully crystalline with perovskite structure. The film deposited at 700°C has columnar growth with electrical resistivity
of about 1.99×10−3Ω cm. The amorphous films grown at 500°C were post-annealed at different conditions. The sample post-annealed at 700°C and
10−4Pa has similar microstructure with the sample in situ grown at 700°C and 25Pa. However, the electrical resistivity of the
post-annealed sample is one magnitude higher than that of the in situ grown sample because of the effect of oxygen vacancy.
The temperature dependence of resistivity exhibits semiconductor-like character. It was found that post-annealing by rapid
thermal process will result in film cracks due to the thermal stress. The results are referential for the applications of
LSCO in microelectronic devices.
Applied Physics A 01/2009; 95(3):721-725. · 1.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The weak antilocalization (WAL) effects of the two-dimensional electron gas (2DEG) in high mobility Al <sub>x</sub> Ga <sub>1-x</sub> N / GaN heterostructure as well as beating patterns in the Shubnikov–de Haas (SdH) oscillatory magnetoresistance have been investigated by means of magnetotransport measurements before and after illumination. The zero-field spin splitting mainly arising from the Rashba spin-orbit coupling effect is studied using the weak antilocalization and beating patterns analysis, respectively. The Rashba spin-orbit coupling constant α deduced using the weak antilocalization analysis showed a good agreement with that estimated from the analysis of the beating patterns for the sample before and after illumination. For our sample, the electron motion in the high mobility system is in the ballistic regime, the experimental WAL curves were fitted by a simulated quantum conductance correction according to a model proposed by [Golub [Phys. Rev. B 71, 235310 (2005)].
Journal of Applied Physics 10/2008; · 2.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Magneto-transport measurements have been carried out on double/single-barrier-doped In0.52Al0.48As/ In0.53Ga0.47As/ In0.52Al0.48As quantum well samples from 1.5 to 60 K in an applied magnetic field up to 13 T. Beating Shubnikov–de Haas oscillation is observed for the symmetrically double-barrier-doped sample and demonstrated due to a symmetric state and an antisymmetric state confined in two coupled self-consistent potential wells in the single quantum well. The energy separation between the symmetric and the antisymmetric states for the double-barrier-doped sample is extracted from experimental data, which is consistent with calculation. For the single-barrier-doped sample, only beating related to magneto-intersubband scattering shows up. The pesudospin property of the symmetrically double-barrier-doped single quantum well shows that it is a good candidate for fabricating quantum transistors.
Solid State Communications 05/2007; 142(7):393-397. · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have observed the weak antilocalization (WAL) and beating SdH oscillation through magnetotransport measurements performed on a heavily δ-doped In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As single quantum well in an applied magnetic field up to 13 T and a temperature at 1.5 K. Both effects are caused by the strong Rashba spin–orbit (SO) coupling due to high structure inversion asymmetry (SIA). The Rashba SO coupling constant α and zerofield spin splitting are estimated and the obtained values are consistent from different analysis for this sample.
Solid State Communications 01/2007; · 1.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electron–electron interaction effect of the two-dimensional electron gas (2DEG) in AlxGa1−xN/GaN heterostructures has been investigated by means of magnetotransport measurements at low temperatures. From the temperature dependence of the longitudinal conductivity of the heterostructures, a clear transition region has been observed. Based on the theoretical analysis, we conclude that this region corresponds to the transition from the diffusive regime to the ballistic regime of the 2DEG transport property. The interaction constant is determined to be −0.423, which is consistent with the theoretical prediction. However, the critical temperature for the transition, which is 8 K in AlxGa1−xN/GaN heterostructures, is much higher than the theoretical prediction.
Physics Letters A - PHYS LETT A. 01/2007; 366(3):267-270.