A New Understanding For The Quantum Confinement In High Al Content AlGaN And Tailorable Orbital-state Coupling

Different atomic orbitals exhibit unique physical properties in quantum structures,and it is difficult to explain by the conventional quantum confinement which is based on continuous potential derived from the heterostructure band offset.Especially in AlGaN semiconductors with high polarization lattice,the interactions between atomic orbitals must be taken into considerations.In this thesis,the deconfinement of quantum state is found,and a new understanding of quantum confinement is studied with the orbital inter-coupling.The orientation of orbitals are sensitive to the confining direction,thus the orbital coupling effects can be tuned through the orbital engineering for efficiently confining quantum states.The orbital engineering presented in this thesis aims to spur on the further improvement of solid state ultraviolet light source.Here we highlight four parts in this thesis:The technique for nanoscale lighting of quantum states study.Through the combination of electron probe,double scanning tunneling probes and fiber probe,the detect of micro-optical and electrical properties is of high precision.Compared to the conventional characterizing methods,this method provide the multiscale analysis aims at the targeted quantum states.It is a breakthrough in both function and performance.The success development of this method provide an important approach to our work.The observation of abnormal radiative interband transitions.Through the investigation of the high Al content AlGaN multi-quantum well based LED,the origin of each excited peak in its cross-section is distinguished by spatial resolution cathodoluminescence spectra.According to the traditional quantum confined models,the band bending is tunable by effective electric field on the quantum structure,and result in the quantum state energies shift.By applying an external electric field to the quantum structure,the abnormal interband transition is observed.By first-principle calculation,the deconfinement of the CH band in the quantum well is responsible for the unusual optical phenomenon.A new understanding for the quantum confinement in high Al content AlGaN.Through the deconfinement of quantum states,the limitation of conventional quantum confinement is found,and deeply analysis through orbital interaction is needed.By theoretical calculation,the orbital orientation would affect the coupling energy as the interaction between p orbitals dependent on the direction of confinement.The atomic orbital interacting energy is joint to offer the barrier potential for quantum confinement.Through this new mechanism,the deconfinement of pz orbital quantum states can be explained.Tailorable orbital-state coupling engineering.Through theoretical simulation,the orientation of p orbital can be tuning to offer better confinement of quantum structure,and achieve an improving in emitting efficiency.Through MOVPE methods,different oriented quantum wells are growing on pyramid microrods experimentally,and the characterization of optical properties confirm the theoretical prediction.The tailorable orbital-state coupling engineering spur on the further improvement of solid state deep ultraviolet source,and also inadequate for the design of structures with strong polarization.