| Summary: | 碩士 === 長庚大學 === 光電工程研究所 === 97 === The AlGaN/GaN HEMT structure in this investigation was growth by MOCVD. The carrier density was obtained by making Hall measurements and from capacitance–voltage (C–V) curves. In the experiment, the values were inconsistent. The carrier density varied with the surface conditions of the samples that were prepared for Hall and C–V measurements.
To study further the effects of the surface conditions on the sheet carrier densities, the samples were annealed at various temperatures that were used MOCVD to anneal for one hour at an environment of H2. Five samples were reloaded into the MOCVD reactor, and separately annealed at 1000℃, 900℃, 800℃, 700℃ and 600℃. The surface of samples random to became defects of hexagonal with SEM (Scanning Electron Microscopy), because Hydrogen pyrolysis with gallium atoms. Then, we were investigated that various temperatures for electrical measurements from the annealed temperature influenced surface condition. The annealed temperature was increased, because surface conditions became badly, and lead to the leakage current became hardly .Because the leakage current were related to the defects, so lead to concentration were lower. Thus, the relationship between surface state and the carrier density was determined.
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