Formation of femtosecond laser-induced periodic nanostructures on GaN

Abstract

The femtosecond laser-induced periodic surface structure (LIPSS) method has attracted considerable interest as a way to form fine structures with dimensions below the laser wavelength. These structures are highly reproducible, demonstrating that this method is suitable for applications such as quantum devices. In this study, we investigated the shape and crystalline state of a LIPSS to clarify the material properties and laser conditions that define its structure. While a LIPSS composed of GaN maintained its crystallinity, disturbances in its local crystalline orientation were generated. The direction and periodicity of the LIPSS did not depend on the in-plane crystal direction of GaN or the scanning direction, but the aspect ratio of each LIPSS depended on the in-plane crystal direction. The LIPSS with exposed {1-100} GaN faces showed high aspect ratios, with narrower widths and deeper depths, than LIPSS with different exposed faces.

Laser-Induced Periodic Nanoripples Generation on Gallium Nitride Using Near-infrared Ultrashort Pulsed Laser

“…Moreover, HSFL formation has a relatively stable period at ~60 nm on the GaN surface. Other research has reported that the width and periods of ripple depends on the in-plane crystal direction of material [6], which we will investigate in a future report. In dielectric materials and semiconductors, models of surface plasmon polaritons (SPPs) and a nano-plasmonic enhancement of laser field can be used to predict the size of LIPSS.…”

“…Furthermore, the polarization shape, laser power, scanning direction, and crystalline dependence of LIPSS formation on GaN has important implications for optimization of this laser processing techniques. By carefully controlling all those parameters, it is possible to create well-defined LIPSS patterns with a desired periodicity, which can be used for various applications, such as surface texturing, anti-reflection coatings, and light extraction enhancement in LEDs [6]. As a response, this paper demonstrates the generation of LIPSS patterns on GaN using a femtosecond laser and predicts the suitable physical mechanism.…”

“…Several LIPSS laser type generation shapes are actively investigated (e.g., with nanosecond and femtosecond lasers [4,5]), and yet still pose many open questions, such as control of periodicity, nanoripples direction, and the physical mechanism. To this end, several models and mechanisms of its generation have been underpinned, including the activation of surface plasmon polaritons, a parametric decay process, second harmonic generation, and surface plasma created by ultrashort pulsed laser irradiation [6]. Furthermore, the polarization shape, laser power, scanning direction, and crystalline dependence of LIPSS formation on GaN has important implications for optimization of this laser processing techniques.…”

Large area uniform femtosecond-laser-induced periodic surface structures fabricated on heated LiNbO3:Fe

“…The rapid development and widespread application of femtosecond (fs) laser with the additional advantages of high peak fluence and minimal thermal effect have opened a new avenue in micro-/nano-processing, which is especially important for wide bandgap and transparent materials. 1,2) The irradiation of solids with linearly-polarized fs laser has been known to result in the formation of laser-induced periodic surface structures (fs-LIPSS), also known as ripples, [3][4][5] which have been observed extensively in metals 6,7) and semiconductors, [8][9][10][11][12] with multifarious irradiation conditions. Due to the novel electronic, optical, and mechanical properties, the fs-LIPSS have broadened the potential applications in the high-tech industry.…”