Growth and Characterization of Position Controlled Droplet Epitaxy Quantum Dots

Abstract

Semiconductor quantum dots have been studied extensively for various quantum optical devices. Recently, it has been demonstrated that single quantum dots have the potential to be used in quantum cryptography and quantum computing. However, in order to realize a practical quantum device for such applications, many obstacles remain. Droplet epitaxy is a versatile method in the growth of quantum nanostructures. The separation of group III materials and group V materials has opened up new possibilities in the growth of nanostructures. By using droplet epitaxy, it is possible to overcome the obstacles which have been associated with conventional self assembled quantum dot growth for quantum optic devices such as single photon emitters. <br/> In this thesis, droplet epitaxy and growth methods derived from droplet epitaxy has been researched for the use quantum optic device applications. The basic growth technique for Ga droplets were experimented with various arsenization processes. An annealing method which improves the optical quality of the quantum dots under a thin capping layer for the use of surface plasmonics was developed with droplet epitaxial<br/> quantum dots.<br/> Among the many uses of metal droplets, an in-situ etching method was studied and used for improved quantum dots. The nanoholes generated by the droplet drilling were used as a template for symmetric quantum dots. Shape symmetry of the quantum dots is an important factor in generating entangled photon pairs, which is used for quantum information devices. The nanoholes were filled with InAs to form In(Ga)As quantum dots. A multistage drilling method was developed to overcome temperature limitations of the<br/> droplet drilling process. The multistage drilling method was also utilized for the position control of the quantum dots by combining it with an AFM lithography method. The results show promising characteristics for quantum optic device applications.