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We study the effects of GaN interlayer on the transport properties of two-dimensional electron gases confined in lattice-matched AlInN/AlN/GaN heterostructures. It is found that the Hall mobility is evidently enhanced when an additional ultrathin GaN interlayer is introduced between AlInN and AlN layers. The enhancement of the Hall mobility is especially remarkable at low temperature. The high Hall mobility results in a low sheet resistance of 23Ω=⧠ at 2K. Meanwhile, Shubnikov-de Haas oscillations (SdH) are also remarkably enhanced due to the existence of GaN interlayer. The enhancement of the SdH oscillations is related to the larger quantum mobility μq owing to the suppression of the interface roughness, alloy disorder, and ionized impurity scatterings by the GaN interlayer. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We report on the strong spin-orbit (SO) interaction in a gated high-mobility In0.53Ga0.47As/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. [ABSTRACT FROM AUTHOR]

We study the magnetotransport properties of a gated In0.53Ga0.47As/InP 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The weak antilocalization (WAL) effects of the two-dimensional electron gas (2DEG) in high mobility AlxGa1-xN/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)]. [ABSTRACT FROM AUTHOR]

The oscillatory magnetoresistance of the two-dimensional electron gas (2DEG) in AlxGa1-xN/GaN heterostructures has been studied by means of magnetotransport measurements at low temperatures and high magnetic fields. The split peaks of the Shubnikov–de Haas oscillations are observed at high magnetic fields, which are attributed to the spin splitting of the 2DEG. It is found that the spin splitting energy becomes smaller with an increase in magnetic field, indicating that the Zeeman spin splitting is not dominant at measured magnetic field range. Within this magnetic field range, the zero-field spin splitting, as well as Zeeman spin splitting, affects the split peaks in the oscillatory magnetoresistance of the 2DEG in AlxGa1-xN/GaN heterostructures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We study the magnetoresistance of a high-density two-dimensional electron gas confined in an InAlAs/InGaAs quantum well and observe a parabolic negative magnetoresistivity at moderate field. This negative magnetoresistivity is induced by electron-electron interactions. The interaction correction to the Drude conductance is extracted from the negative magnetoresistivity. However, due to inhomogeneity in the electron density, there is a contribution of positive magnetoresistivity, which induces the larger extracted correction than anticipated. [ABSTRACT FROM AUTHOR]

The weak antilocalization effects of the two-dimensional electron gas in a high mobility AlxGa1-xN/GaN heterostructure 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 as a function of electron concentration as well as a function of temperature is studied using the weak antilocalization analysis. The Rashba spin-orbit coupling constant α deduced using the weak antilocalization analysis shows a rapid decrease with the increase of the measured electron concentration. [ABSTRACT FROM AUTHOR]

Crystalline microporous Co11(HPO3)8(OH)6 nanowires have been synthesized through a soft hydrothermal reaction between red phosphor, KOH, and metal halides. These nanowires were found to have their main hexagonal channels along the long axis and a narrow distribution around 30–40 nm in diameter. The growth of the nanowires were found to initiate at Co(OH)2 nuclei. The length of the nanowires depends mainly on the hydrothermal reaction time and the amount of Co(OH)2 available at the nuclei to feed the growth of the nanowires. Blue shift of up to 85 nm was observed in UV-visible absorption spectra from the Co11(HPO3)8(OH)6 nanowires in comparing with that from the micro-size particle sample, giving an absorption edge deep in the ultraviolet region at about 255 nm or a bandgap Eg∼4.9 eV. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]