Investigation of Nonlocal Conduction in Two Dimensional Electron System Controlled by Various Gate

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We have investigated 2DES in semiconductor with various gate structures and obtained the following results.(1) Magnetocapacitance in the Quantum Hall RegimeWe have measured the temperature and frequency dependence of the magnetocapacitance minima between 2DES and the gate GaAs/AlGaAs in QHE regime. It is found that we can separate the capacitance which is prportional to the area of the edge state and that from the bulk state, which is a function of sigma_<xx>.(2) Nonlocal Resistance and Edges State in GaAs/AlGaAs and Si-MOSFETFrom the nonlocal magnetoresistance in QHE regime, it is determined that energy relaxation lengh of edge state in GaAs/AlGaAs and Si-MOSFET is several cm and several hundred of microns.Reflection from Extra Probes in Magnetic Electron Focusing EffectWe have found that the electron in apparently reflected from the extra probe in MEFE and the reflected electron comes from the remitted electron from the extra probe, whose potential increases due to the pile of electrons.(4) Angular Distribution of Electron from Oblique WireWe have determined the angular distribution of electron from the oblique wire by the ballistic electron transport at low magnetic fields. The emitted distribution is found to depend on the structure at the outlet rather than the wire direction.(5) Commensutate Oscillations in Artificial Antidot SuperlatticeWe have investigated the influence of current direction and the anisotropy of superlattice on the commensurate oscillations in antidot superlattice. It is found that the peak position of the oscillations is determined by the nearest neighbor distance except for the direction of nearest neighbor parallel to the current.(6) Electron Localization Effect in poly-Si TFTFrom the low temperature electrical measerement of poly-Si TFT,it is found that the TFT samples show various Anderson localization phenomena from the 2D weak localization to the variable range hopping due to the strong localization.