Fabrication Of Flexible Al_xGa_1-xAs Thin Film And Analysis On Its Optical Property

With the widespread development of wearable electronics, to meet the requirement of real-time monitoring, future electronic devices should have the function to fit the surfaces of different shapes, e.g. human skin, to collect and analyze data. The method of constructing conventional high-quality electronic material and soft polymer substrate into a mechanical structure to realize flexibility and even stretchability has already attracted huge focuses. Among these mechanical designing, buckling has been proved to be an effective way to achieve the abilities. When buckling formed in brittle inorganic material film which has been transferred onto soft substrate, the formative system can bear the hypernormal strain which is beyond material fracture limit but not to fail. In this thesis, based on multi-layer Al_xGa_1-xAs film, we transferred it onto Polydimethylsiloxane（PDMS） from hard GaAs native substrate and then made it buckling. Significantly, we put effort on studying the process of buckling, the effect of buckling on film’s stretchability as well as the material bandgap tuning with buckling profile.Addressed to above subjects, firstly, we have done research on the change of Young’s modulus with ratio of pre-polymer and cross-linker. Combing to the result, we have determined the last ratio of 10:1 in our experiment. Moreover, we studied on the curve of Young’s modulus versus temperature under the determined ratio with 1.5mm thickness. The analysis provided a precise mechanical parameter for later theoretical calculation.After the discussion on mechanical property of PDMS, we successfully transferred ribbon multi-layer Al_xGa_1-xAs film onto pre-treated PDMS substrate by undercutting the sacrificial layer of Al0.9Ga0.1As from GaAs substrate and then by applying thermal expansion method we realized buckling on ribbon Al_xGa_1-xAs film. Comparison between measured sizes of buckled film by 3D microscopy and the theoretical sizes revealed identity that our experimental result accords with one-dimensional buckling theory. Furthermore, with the help of stretching platform, the Al_xGa_1-x As film with one-dimensional buckling was proved to possess uniaxial stretchability that exceeds material fracture limit. Similarly, we also exhibited another buckled model which could endure biaxial stretching in the thesis.In the last, by the characterization of Raman spectra and Photoluminescence（PL） spectra, we analyzed the strain and the bandgap distribution in some specific positions on the surface of the film. The analytical conclusion showed that the bandgap of buckled Al_xGa_1-xAs is periodically modified by the periodic strain which is resulted from the buckling profile. Hence, we considered this kind of periodic modification will have a prospective application in some novel fields where periodic-property tuning is demanded.