Research On The Characteristics Of Ⅲ-ⅤSelf-Rolled-Up Microtubes

Three-dimensional III-V semiconductor self-rolled-up microtubes are becoming an academic research hot spot because of their great potential applications in micro-electromechanical systems (MEMS) and biosensing. Particularly, the research on the Si-based Ⅲ-Ⅴ semiconductor self-rolled-up microtubes is significant for the development of silicon photonics. In comparison with other fabrication techniques of micro-and nano-structure, the fabrication process of Ⅲ-Ⅴ self-rolled-up microtubes combines advantages of the "bottom-up" pseudomorphical growth with "top-down" traditional photolithography and wet etching, resulting in a smooth epitaxial surface with controllable radius and morphology of the self-roll-up microtubes.The thesis is focused on the fabrication and morphological and optical properties of GaAs-and Si-based Ⅲ-Ⅴ semiconductor self-rolled-up microtubes. The main achievements are listed below.1. GaAs-based self-supporting self-rolled-up microtube array and Si-based self-supporting self-rolled-up microtubes have been fabricated by using In0.2Ga0.8As (15nm)/GaAs (35nm) pseudomorphically strained epitaxial bilayers through U-shaped mesas method. The results of scanning electron microscope (SEM) show that the radius of Si-based microtubes is slightly smaller than that of the GaAs-based counterpart.2. Self-supporting self-rolled-up InGaAs/GaAs Ⅲ-Ⅴ semiconductor microtubes with single GaAs/AlGaAs quantum well have been obtained. InGaAs/GaAs strained bilayers with2nm-thick Au membrane deposited rolled up into self-supporting microtube, which lays the foundation of the fabrication of self-rolled-up microtubes devices.3. Micro-PL measurements were used to characterize the photoluminescence of GaAs-and Si-based non-self-supporting InGaAs/GaAs microtubes. The results show that the PL intensity of microtube is stronger than that of as-grown strained membrane, and becomes stronger with the increment of number of turns, which is attributed to an enhancement of light confinement in the microtube wall. In addition, the peak of microtube exhibits a redshift compared with that of the as-grown strain membrane due to the release of the built-in strain.4. The strain characteristics of GaAs-and Si-based self-rolled-up InGaAs/GaAs microtubes have been studied by micro-Raman measurements. The results show that both the longitudinal optical (LO) and transverse optical (TO) phonon modes of GaAs material exhibit a blueshift (-3cm-1) after the InGaAs/GaAs strained membrane rolled up to be microtube, and the peak positions of LO and TO are independent with the number of turns, suspending or not as well as the measurement position along the axial direction.