Shinji Kawaji

The Two-Dimensional Lattice Scattering Mobility in a Semiconductor Inversion Layer

A theory of two-dimensional lattice scattering for electrons or holes in a semiconductor inversion layer is described. The theory can explain the electron mobility in Si inversion layers at room temperature taking the two-dimensional deformation potential constant as 23±1 eV.

Negative Magnetoresistance in Silicon (100) MOS Inversion Layers

The observation of the negative magnetoresistance in silicon (100) n-channel inversion layers is well reproduced by the recent theory for the random potential scattering in two dimension by Hikami, Larkin and Nagaoka. The parameter α is 0.30±0.05 at an areal concentration of electrons of 5.0×10 12 cm -2 .

Surfons and the Electron Mobility in Silicon Inversion Layers

Surfons are acoustic phonons in a body with surfaces, having both bulk and surface modes. To account for the electron mobility µ in Si inversion layers in the range of surface electron density Ns=(0.5~5)×1012 cm-2 and temperature T=200~300 K, scattering due to the surfon deformation potential is calculated. Qualitative features of the calculated mobility µcalc such as its dependence upon Ns and T, its variation with the surface orientation and its anisotropy agree with experiments. Quantitatively, however, µcalc is about three times as large as the values measured so far, when the estimated scattering by optical phonons is taken into account. The effect of the phonon reflection on the surface is about 15%. The theory uses the deformation potential constants and all the other parameters from bulk measurements. Some of these values could perhaps be different in the surface region, or the value of the mobility may become bigger as sample preparation techniques improve further so that the discrepancy may be less pronounced.

Quantum galvanomagnetic experiments in silicon inversion layers under strong magnetic fields

Abstract Experimental research so far made in our group on galvanomagnetic phenomena for n-type (001) silicon inversion layers in the quantum regime is described. Particular emphasis is given to measurements of the conductivity tensors for a normal two-dimensional electron gas and localized electrons both under strong magnetic field. The spectroscopic aspect of quantum transport experiments on SOSMOS systems is also described.

Breakdown of the Quantum Hall Effect in GaAs/AlGaAs Heterostructures Due to Current

Properties of the breakdown of the quantum Hall effect due to current have been measured in specially designed samples with the width ranging from 10 to 120 µm made from a GaAs/AlGaAs heterostructu...

Temperature dependence of the magnetoconductivity in the ground Landau level in silicon inversion layers

Abstract The magnetoconductivity σ xx in the lower edge of the lowest Landau level in silicon inversion layers shows an activation type temperature dependence in H = 97.5 kOe and T = 4.2−1.5 K. An attempt is made to describe the experimental results by a simple model based on the quantum diffusion of Schottky defects in the two-dimensional Wigner crystal.

Device-width dependence of plateau width in quantum Hall states

Abstract Hall bar type devices having a total length of 2900 μm, a source and drain electrode width of 400 μm and different widths w ranging from 10 to 120 μm in its central 600 μm long part are fabricated from a GaAs/AlGaAs wafer with electron mobility of 21 m 2 V −1 s −1 . The current at which the quantum Hall plateau for i =2 at B =9.7T at T =1.2K disappears is proportional to w . The average critical current density is J cr =(1.6±0.2) A m −1

Experiments on the Critical Exponent of Localization in Landau Subbands with the Landau Quantum Numbers 0 and 1 in Si-MOS Inversion Layers

Temperature ( T ) dependence of the mobility edge is examined by a model calculation which reproduces the experimental line shape of dσ x y /d N s (σ x y : Hall conductivity, N s : electron concentration) for (0↓-) and (1↑-) Landau subbands in Si-MOS inversion layers in the range of 0.35 K≦ T ≦1.5 K and in a magnetic field of 15 T. The result show that the critical behaviour of localization depends on the Landau quantum number.

Temperature Dependence of Transverse and Hall Conductivities of Silicon MOS Inversion Layers under Strong Magnetic Fields

An n-channel MOS inversiln layer on Si (100) surface is a typical two-dimensilnal electrln system. When a strlng magnetic field is applied along a directiln nlrmal tl the Si-SiO2 interface, the continuum of electron energy levels in two-dimensilnal mltiln clalesces intl a series lf perfectly quantized Landau levels [1], In such a system in an extreme-quantum-limit clnditiln, there exist gap regilns in the density of states of electrons between the boundaries of each Landau level.

FIELD EFFECT MEASUREMENTS ON THE A AND B (111) SURFACES OF INDIUM ANTIMONIDE.

Abstract Large signal alternating current field effect experiments have been performed at 113° K on the A and B {111} “real” surfaces of InSb exposed to different ambients. Discrete fast surface states were observed in the energy gap near the valence as well as near the conduction band edge on both types of surfaces. The discrete state near the conduction band edge exhibited essentially the same density on the A and B surfaces, while the state near the valence band edge was found to be more dense on the B surface. In all cases, both surfaces were p-type, the B surface being invariably more p-type than the A surface. A model is presented according to which the surface state near the conduction band edge is acceptor-like and characteristic of the In atom while the surface state near the valence band edge is also acceptor-like but characteristic of the Sb atom. This model is consistent with the Gatos-Lavine model of the polar surfaces of the III-V compounds.