| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 94 === 1. Studies of electron heating in a GaAs/AlxGa1-xAs heterostructure at low temperatures
In recent studies of two-dimensional electron transport at low temperature in GaAs/AlGaAs heterojunctions one normally investigates degenerate electron systems with mobilities which can exceed 10^5cm^2/Vs. At liquid helium temperatures, the only technique that has successfully been used to determine the electron temperature of hot electron at heterojunctions is using the amplitude of Shubnikov-de Haas (SdH) oscillations in the resistivity subjected to various applying currents I. In this work, we shall show that in our system joule heating E^2 is proportional to Te^3-TL^3 where TL is the lattice temperature and E is the applying electric fields. It is interesting to note that for a fixed heating current I, Te appears to increase with increasing magnetic field B. Finally we find that Te ~ I^(0.52) at various B, in good agreement with recent experimental work on broadening of the resistivity peaks.
2. Studies of electron heating of GaAs/AlxGa1-xAs heterostructure in QH regime at low temperatures
We will treat the same physics properties of heating electron in different magnetic fields range, which is enough to separate spin up and down in Landan levels as increasing magnetic fields. At filling factors 3, 5, 7, and 11, the behavior of minimum longitudinal resistivity obey the equation of activation energy, So we can derive Te using the activation equation, and also find the power law behavior at I > 10^(-9)A in those ranges. Finally we find that Te ~ I^(0.45) at odd-integer filling factor. From the mobility gas.
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