Optical Phonon-Assisted Resonant Tunneling In Multilayered Semiconductor Materials

In this thesis, within the framework of the dielectric continuum model, we investigated the dispersion relation of optical phonon modes and the interaction between an electron and different kinds of optical phonons in multilayered semiconductor materials using a transfer matrix method. Furthermore, the emitting probabilities of phonons are calculated using the Fermi golden rule and the phonon-assisted tunneling current to investigate the assistant role on resonant tunneling from optical phonons.1. The dispersion relations of interface optical phonon modes and the interaction between an electron and interface optical (IO) phonons in AlxGa1-xAs/GaAs double barrier structures consisting of ternary mixed crystals have been discussed theoretically in detail. Furthermore, the optical phonon-assisted tunneling (PAT) is discussed for the barriers and wells being ternary mixed crystals, respectively. It is found that only one phonon-assisted tunneling peak appears for ternary mixed crystals as barriers. This conclusion agrees well with that given by experiments: Whereas, the effect of ternary mixed crystal is obvious, that two phonon-assisted tunneling peaks appear for ternary mixed crystals as wells. The effect of pressure on tunneling current has been also discussed. The result shows that the PAT peaks and the resonant tunneling peak are reduced with the pressure increasing. The effect of phonon-assisted tunneling is increased with the pressure.2. The interaction between an electron and optical phonons and phonon assistant role on the tunneling in a AlxGa1-xAs/GaAs coupled-quantum-wells are discussed. The results show that, among the influences on the tunneling from different phonons, IO phonons are more important. Only one PAT peak does appear when the middle barrier is wide enough or its Al component is high enough because the energies of IO phonons and confined longitudinal optical phonons are almost equivalent. The peak moves to the lower applied voltage direction, whereas two PAT peaks do appear when the middle barrier is narrow enough or its Al component is low enough. When the middle barrier is narrow and its Al component is low, more information about phonons can be demonstrated.3. The different modes of optical phonons in wurtzite InxGa1-xN/GaN double barrier structures are calculated. Furthermore, the interaction between an electron and optical phonons in these structures are investigated. Moreover, the influences on the currents of PAT from different kinds of optical phonons are given. The results reveal that the IO phonons play an important role in the process of PAT.The above results enriched the related theory and can be helpful to experiments and device design.