Fabrication of Photonic Crystal Structures on GaAs by Single Pulse Laser Interference Lithography

Photonic crystal (PhC) structures generated through periodic surface nanostructuring are pivotal for controlling light-matter interactions. These structures are essential for reducing high surface reflectivity in semiconductor optical devices, enhancing light absorption in photovoltaic cells, and improving light extraction in LEDs. Although various methods for PhC fabrication are well-documented, the use of single-pulse laser interference lithography (LIL) with commercial photoresists remains unexplored. Single nanosecond pulses for photoresist exposure offer significant advantages, including high throughput for large-scale patterning and reduced dependence on stable optical platforms. In this study, we used single-pulse LIL to fabricate antireflective PhC structures on GaAs substrates using a commercial photoresist. This process involved exposing the photoresist to single 7 nanosecond pulses at a wavelength of 355 nm, with relatively low energy levels. High-quality nanohole arrays were subsequently created via inductively coupled plasma (ICP) etching. Reflectivity analysis revealed that these structures reduced the average reflectance of GaAs to below 5% across the visible wavelength range of 450-700 nm. This work is crucial for optimizing current photonic technologies and advancing future devices with enhanced light management capabilities.