Surface quantum oscillations in tellurium inversion layers

We report results and the analysis of properties of the two-dimensional inversion layer in the [0001] plane at the surface of tellurium, showing special features associated with the dispersion relation of the conduction band of tellurium.     

Surface quantum oscillations in n-type (100) silicon inversion layers on sapphire

Measurements of Shubnikov-de Haas oscillations in (100) Si/($\text{1}$012)Al₂O₃ MOSFET's were performed in magnetic fields up to 10 Tesla for different tilt angles between the magnetic field direction and the surface normal. The experimental results show that the lowest electric subband in this system is twofold degenerate and is formed by the “heavy” cyclotron mass valleys. This can be explained by a large lateral stress present in the SOS (silicon on sapphire) system.     

Surface quantum oscillations in (100) inversion layers under uniaxial stress

Surface quantum oscillations have been measured with uniaxially stressed (100) n-type inversion layers. A relation between mechanical stress and cyclotron mass m_c has been observed. In the quantum limit the two-fold valley degeneracy is lifted by about 1 meV with compression.     

Surface quantum oscillations in (110) and (111) n-type silicon inversion layers

Shubnikov-de Haas oscillations have been studied for (110) and (111) n-type silicon inversion layers. The measured cyclotron masses m_c = (0.38 ± 0.03)m₀ and m_c = (0.40 ± 0.03)m₀ for (110) and (111) planes, respectively, are larger than theoretically predicted values. The experimental valley degeneracy factor g_v = 2 ± 0.2 for both orientations is also at variance with self consistent calculations. The electronic g-factor depends on the surface carrier concentration and is enhanced over its bulk value. There was no evidence for the occupation of other subbands.     

Shubnikov-de Haas oscillations in p-type inversion layers on n-type silicon

Surface Shubnikov-de Haas oscillations have been measured in p-type channels of (110) silicon field effect transitors between 1.4 and 4.2 K in magnetic fields up to 10 Tesla. Two electric subbands were revealed and the effective masses of the holes in both bands could be determined. For one subband the dependence of the mass on the surface electric field was investigated. At low gate voltages the g-factor of the holes was measured from the spin splitting of the Landau-levels.     

Influence of uniaxial stress on quantum effects in Si inversion layers

We show that the application of a compressional stress to the Si substrate decreases the mobility of electrons in the lowest subband and causes piezoresistance. This effect, together with the electron transfer effect and the existence of localized band-tail states in the subbands at low electron densities, account for the piezoresistance in n-channel (100)Si inversion layer at 4.2 K.     

Far infrared emission from plasma oscillations of Si inversion layers

We observed narrow-band far infrared emission from Si-MOSFETs with metallic gratings fabricated on the optically semitransparent gate. The gate voltage dependence of the emission frequency, analyzed by a magnetic field tuned detector, shows that it results from radiative decay of the two-dimensional metallic grating.     

Surface optical solitons in semiconductor quantum dot layers

A theory of optical solitons under the condition of nonlinear coherent interaction of surface TM-modes with a layer of inhomogeneously broadened semiconductor quantum dots is developed. Explicit analytical expressions for a surface soliton (2π-pulse) in the presence of single and biexciton transitions are obtained in the regime of self-induced transparency with realistic parameters which can be reached in current experiments.     

Surface optical solitons in semiconductor quantum dot layers

A theory of optical solitons under the condition of nonlinear coherent interaction of surface TM-modes with a layer of inhomogeneously broadened semiconductor quantum dots is developed. Explicit analytical expressions for a surface soliton (2π-pulse) in the presence of single and biexciton transitions are obtained in the regime of self-induced transparency with realistic parameters which can be reached in current experiments.     

Surface oscillations and the surface thickness of classical and quantum droplets

We calculate the contribution from surface oscillations to the surface thickness of a liquid drop. The results are compared to those for a surface made plane by gravity. We find that the zero-point motion of the surface modes gives a contribution to the surface thickness which is independent of the drop radius R, and is in good agreement for liquid He⁴ with other estimates of the surface thickness. For classical droplets, the mean square displacement of the surface varies as log R, in accord with the plane surface results.     

Magnetophonon oscillations in tellurium under hot carrier conditions

The magnetoresistance of undoped tellurium crystals was measured at lattice temperatures below 4.2 K and magnetic fields up to 15 T. Under hot carrier conditions two series of magnetophonon oscillations in the longitudinal magnetoresistance with the c-axis perpendicular to the magnetic field direction were observed. On the basis of the known band parameters and an impurity binding energy of 1.4 meV, the results are explained with the capture of warm carriers at impurity sites under optical phonon emission.     

Shubnikov de Haas oscillations in n-type inversion layers on (110) and (111) surfaces of Si

Oscillatory magnetocunductance of electrons on (110) and (111) surfaces of Si have been observed. The ground-state degeneracies were determined and possible energy level schemes are proposed.     

Magnetoresistance of inversion and accumulation layers in MOS structures on pSi (100)

The magnetoresistance of two-dimensional electron and hole gases in MOS structures onpSi (100) was studied in inversion and accumulation regimes, respectively, measurements being made without contacts using a new experimental technique. In the magnetic field (h < 7 T) parallel to the sample surface the positive magnetoresistance was established to depend on a combination H/T^α (α ≈ 0.5, 1.7 ? T ? 4.2 K), that is unexplainable in terms of modern theories of electron localization and electron-electron interaction. In the perpendicular field, the magnetoresistance of p-accumulation layer is positive and comparable in magnitude with that in the parallel field.     

Quantum oscillations in an inversion layer on p-PbTe

We report the observation of a variable density inversion layer on p-PbTe. The carriers in the inversion channel are found to have a mobility on the order of 250,000 cm² V^-1 sec^-1. Shubnikov-de Haas oscillations in the channel conductivity were measured in magnetic fields up to 6 T. From the observed periodicity we conclude that the oscillations represent only a fraction of the total number of electrons in the channel.     

Magnetic quantum oscillations in nanowires

Analytical expressions for the magnetization and the longitudinal conductivity of nanowires are derived in a magnetic field, B. We show that the interplay between size and magnetic field energy-level quantizations manifests itself through novel magnetic quantum oscillations in metallic nanowires. There are three characteristic frequencies of de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) oscillations, F = F(0)/(1 + gamma)(3/2), and F(+/-) = 2F(0)/|1 + gamma +/- (1 + gamma)(1/2)|, in contrast with a single frequency F(0) = S(F)plankc/(2pie) in simple bulk metals. The amplitude of oscillations is strongly enhanced in some magic magnetic fields. The wire cross-section area S can be measured using the oscillations as S = 4pi(2)S(F)plank(2)c(2)/(gammae(2)B(2)) along with the Fermi-surface cross-section area, S(F).     

Hall effect measurements on silicon inversion layers

Hall mobility measurements have been made in the region of activated conductivity. The results are inconsistent with the mechanism being activation to a mobility edge, but agree with a new model of correlation-dominated transport, developed by Adkins.