Studies on Quantum Transport Mechanism of Si Quasi-One-Dimensional Carrier Systems by a Time-of-Flight Method with Pulse Lasers

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The purpose of this work is to realize the low-dimensional carrier system in silicon and to make clear the transport mechanism in this system. We have examined the relationship between the fabrication condition of one-dimensional systems and the observed carrier transport mechanism. The life time of carriers in Si_<1-x>Ge_x/Si systems has been studied by means of the Time-of-Flight method. Si_<1-x>Ge_x/Si films are expected as a material for realizing low-dimensional systems on silicon.Electrical conductive wires of p-Si were fabricated on n-Si by FIB.The current-voltage characteristic was measured in the temperature range of 2K to 300K.Three kinds of characteristic transport can be observed ; the metallic conduction, the nearest neighbor hopping conduction, and the one dimensional variable hopping conduction. There exists a systematic relationship between the observed transport mechanism and the fabrication condition. In the experiments, it can be concluded that the transport mechanis … More m in the wire are controlled by changing the annealing temperature and the impurity dose.The information of localized states in the hopping conduction were studied with the measurements of transverse magnetoresistance. The negative magnetoresistance is observed on the sample with low impurity concentrations, for the sample with the nearest neighbor hopping conduction above 15K, which suggests the existence of Anderson localization. On the other hand, in the strong magnetic field, the positive magnetoresistance appears for all samples. The analysis of the positive magnetoresistance indicates that the localization is due to the confinement by the Coulomb potential. These facts mean the existance of two kinds of localized states.The Time of Flight method with pulse lasers was used for the study of transport phenomena in nano-scale semiconductor devices. In this experiments, undoped Si_<1-x>Ge_x thinfilms were selected as a test material. We have obtained the relationship between the carrieer life time and the amount of the defects. In conclusion, the method is useful for evaluating the life time and the localized state density. Less