Study on formation of three-fold symmetric group III-nitride quantum dot using self-limited growth mechanism: Towards generation of polarization entangled photon pair

Abstract

Epitaxial semiconductor quantum dots (QDs) have been attractive to a quantum light source that emits a single photon as well as a polarization entangled photon pair because the QD can imitate the energy structure of an atom. Specifically, in principle, nitride QDs contribute toward polarization entanglement because of six-fold in-plane rotational symmetry and strong carrier confinement. However, the irregular shapes of the QD from the self-assembly method lower symmetry, which limits the demonstration of the polarization entanglement. In this thesis, the method for the formation of a three-fold symmetric group III-nitride quantum using a self-limited growth mechanism was investigated. The three-dimensional pyramidal structures were formed with selective area growth during a metalorganic chemical vapor deposition. In particular, the morphology evolution of unconventional triangular GaN pyramids was investigated. Moreover, the width of the finite truncation was controlled at the apex of the pyramid under the self-limited growth mechanism, and the triangular nitride QD was formed at the truncation. The triangular QD exhibit the suppression of fine structure splitting as compared to the previous self-assembled QDs. The calculation results support the optical property of QD, which is based on the k∙p theoretical model accompanied by a configuration interaction method. As a result, the control of the symmetry of nitride QD is available through the method proposed in this thesis. Therefore, this work suggests that a polarization-entangled photon emitter can be realized using a group III-nitride QD in the future.