Research On The Key Properties Of Gaas-BasedⅢ-Ⅴ Self-Rolled-Up Microtubes

There has been considerable recent research on the semiconductor self-rolling microtubes worldwide, because they possess massive potentials to provide a wide range of functionalities for optoelectronics、 plasmonics、microelectromechanical systems (MEMS), and sensing. Especially, III-V self-rolled-up microtubes attract great attention. When strained membranes are released from the substrate, they roll up to microtubes by releasing strain. Microtubes/nanotubes with diameter ranging from a few nanometers to micrometers can be realized through changing the strained membrane structures. The fabrication process combines the bottom-up design of material structure and top-down patterning via photolithography.To realize the highly ordered arrays of microtubes and their application, the self-rolled-up mechanism should be elucidated. Although some reports about the self-rolled-up mechanism, there are still some controversies.In this dissertation, GaAs-based III-V strained membranes will be used to investigate the self-rolled-up mechanism. The characteristics of microtubes will be studied as well. The main research works and achievements are listed as follows:1. The highly ordered arrays of InGaAs/GaAs microtubes with18×9the basic unit are realized by using the rectangle mesas with aspect ratios varying from1to3. The length of microtubes are varying from10μm to100μm, the tube-wall thickness is3μm or5μm. The experimental results show that all the rectangle strained membranes roll from the long-side. Comparing the critical point drying to the natural drying in the air, we found that critical point drying avoid the doubly curved regions to appear at the two ends of self-rolled-up microtubes. In addition, microtubes are also fabricated by U-shaped mesas.2. According FEM model is designed to calculate the entire evolution of strain energy during the self-rolled-up process to elucidate the preferential long-side rolling of rectangle mesas. The calculated results show that the long-side rolling behavior has lower strain energy in the intermediate rolling states (The reason is that membranes rolling from the long-side possess more strain-released regions). Therefore, long-side rolling behavior is proved to be preferential.3. The optical properties of microtubes fabricated by the rectangle mesas are studied by photoluminescence. Optical modes in InGaAs/GaAs microtubes ring resonator are investigated through FEM, showing that just TE modes exist when the tube-wall thickness is much smaller than the light wavelength.