| dc.description.abstract | In this thesis, we demonstrate the micro-optics components fabricated in GaN-based materials. GaN diffractive microlenses are designed based on the optical path difference method. Gray-level mask is used to fabricate the diffractive microlenses on GaN epitaxial layer grown on sapphire substrate. The patterns of the microlenses are first formed on the photoresist deposited on GaN. The smooth microrelief on the photoresist is then transferred onto the GaN layer by inductively coupled plasma dry etching technique to form the diffractive microlenses. Three GaN diffractive microlenses are characterized with He-Cd laser, at the wavelength of 442 nm. The measured focal lengths are of the range of 1260~1650+100 ?m.
In this work, to our knowledge, gratings on GaN membrane were also first demonstrated. First, GaN with the thickness of 1?m was grown (111)-oriented Si by metal organic chemical vapor deposition. Secondly, photolithography and dry etching are used to define the grating patterns on the GaN layer. The period of the gratings is 20 ?m and the etching depth is 0.15 ?m. The both sides of the sample are covered by Ni-Cr/Au metal thin films. To remove the Si below the gratings, a rectangular window is opened by etching the metal thin films on the back side of the sample. An isotropic wet etchant, HNA (composition of HNO3, HF and CH3COOH), is used to remove the Si in the window. Finally, after removal of the metal thin films by wet etching, the GaN membrane gratings are obtained.
Due to the high transparency of the GaN-based materials such as AlGaN and InGaN in blue and UV regions, the stacked GaN-based components can be used in the applications of the UV micro-optics system. | en_US |