Semiconductor Nanowire-based Optoeletronic Device Fabrication And Its Characteristics

Semiconductor nanowire optoelectronic devices have attracted intense interests, concerning the advantages of nanowire growth, fabrication, architecture, functionality, etc. A lot of prototypes, such as nanowire photode tec tors, solar cells, light emitting diodes, lasers, have been studied. The nanowire building-block growth and related "top-down" and "bottom-up" combined fabrication, as a new strategy, potentially break through the limitation of the traditional micro-fabrication. The device architecture at the feature scales exhibit unique physical behaviors and promise extraordinary functions. Therefore, the interdisciplinary study of nanowire and optoelectronics is significantly valuable. To develop the nanowire optoelectronic application, researches have been focused on several key issues:high-quality nanowires, optimum architecture, reliable and compatible fabrication, electrical and optical characteristics.In this work, the research progress of nanowire optoelectronic devices has been systematically surveyed. A sequent study has been carried out, including the ZnO nanowire non-catalyst growth, lateral electrode fabrication, photodetection, interfacial transport and optical resonances.A method of fabricating the lateral electrodes on nanowires is developed, which provides a large contact area, a short transport path in diameter and compatibility for varied building-block geometries. The method involves with the nanowire transfer and the anodic oxidation. Metallic electrodes enable to be evaporated on the oppositely lateral sides of the nanowires, while the structurally matched alumina insulates the electrodes, without rigorously precise fabrication. Directional ion migration under electrochemical high-field model attributes to the structurally matched insulation. The insulator layer exhibit qualified properties of leakage and breakdown for the applied bias of further optoelectronic applications.A Schottky-type and a MIS-type UV photodetectors are constructed based on the lateral electrode architecture. The Schottky photodetector exhibits a on/off ratio of6000, a cut-off wavelength near380nm and zero-bias photoresponse behavior, with Au as the semi-transparent electrode. The photoresponse originates from the enhanced transport because of the interfacial-state related barrier reduction. Furthermore, the interfacial transport inhomogeneity is studied in a nanowire ensemble device with the discrete structure and instantaneous interfacial state. A modification of the ultra-thin Al2O3insertion is introduced to construct a MIS photodetector. Stable and rapid photoresponse is exhibited, with a high on/off ratio. The homogeneous tunneling across the uniform and conformal insertion layer contributes to the improvement, which is analyzed by direct and Fowler-Nordheim tunneling models.Polarization photodetection is integrated in the nanowire photodetector, with50%enhancement of polarization ratio. The optical resonances in the metal-nanowire cavities is analyzed by FDTD simulation. The photocurrent varied with the angel between the excitation polarization and the nanowire orientation. The optical absorption is related to the Fabry-Perot resonance under TE and the surface plasmon resonance under TM. The electric field distribution and the Poynting vector certify the relationship of polarization photodetection and the optical resonances, calculated with varied incident wavelength and diametrical geometries.