Ordered Quantum Dots Lattice Growth and Studies of Semiconductor Quantum Rings
|關鍵字:||分子束磊晶;半導體;砷化鎵;砷化銦;量子點;量子環;molecular beam epitaxy;semiconductor;GaAs;InAs;quantum dot;quantum ring|
This dissertation consists of two parts: ordered quantum dots lattice growth and semiconductor quantum rings structures. In the first part, selective growth methods on patterned substrates to achieve position- and number-controlled self-assembled quantum dots were proposed and demonstrated experimentally. In the second part, the growth and characterization of self-assembled semiconductor quantum rings were discussed. As regards QDs selective growth, two approaches of patterned substrates were used in this dissertation. First of all, a high quality crystalline and long-range ordering of QDs array was obtained by making use of different migration behaviors on the faceted surface generating by e-beam nanolithography and wet chemical etching. Besides, a new technique based on strain accumulation was developed for achieving single QDs fabrication. Using this method, 2D ordered single QDs lattice have been demonstrated. In the following, studies and fabrication of self-assembled semiconductor In(Ga)As quantum rings on (100) GaAs substrate were discussed in detail. Using AFM measurements, four main growth parameters, GaAs capped growth rate, GaAs capped temperature, annealing temperature and annealing time, have been studied and discussed respectively. We found that the dewetting process is the dominant mechanism in the formation of quantum rings, and the diffusion-driven transformation greatly influences the surface morphology and composition distribution. Furthermore, a new growth technique based on the diffusion barrier method was developed to solve the problem that the fabrication of quantum rings is strongly dependent on the growth conditions traditionally. An additional AlAs layer impedes the inward diffusion of the Ga and Al atoms and results in nano-ring formation with a more relaxed growth condition.
|Appears in Collections:||Thesis|
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