| Summary: | 碩士 === 國立交通大學 === 電子物理系 === 89 === Abstract
The samples of single InAs/GaAs QD and superlattice InAs/GaAs QDs with RTA (rapid thermal annealing) at different temperature are investigated by capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS) measurement. The C-V measurement shows carrier confinement for 2.3ML single QD and 7.56Å superlattice QDs samples. And the carrier depletion by lattice relaxation is observed in 3.4ML QD sample. For the 2.3ML single QD sample, the quantum-confinement peak concentration of at low temperature is higher than at room temperature. However, in superlattice QDs, the quantum peak concentration is found lower at low temperature than at room temperature. These effects are found to reduce for samples after annealing at high temperature. In contrast with the 2.3ML single QD sample which no traps is found, three traps at 0.63, 0.51 and 0.37eV are detected in the 3.4ML single QD sample. The trap at 0.63eV has been found in plastic deformation GaAs bulk material. The traps at 0.51 and 0.37eV are found similar to the traps observed in relaxed 1000Å In0.2Ga0.8As/GaAs single quantum well structure and are suspected to be related to lattice relaxation. In superlattice QDs samples, two traps at 0.39 and 0.54eV are detected. The trap at 0.54eV is similar to the 0.51eV trap found in 3.4ML single QD indicating that the superlattice QD sample is relaxed. Moreover the
concentration of both traps can be decreased with increasing RTA temperature.
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