Fabrication of sub-micrometer periodic nanostructures using pulsed laser interference for efficient light trapping in optoelectronic devices

Surface nano-texturing can play an important role for efficiency enhancement of light emission and absorption in optoelectronic devices through reduced surface reflection or enhanced broadband absorption. Periodic and uniform semiconductor nanostructures are highly applicable in bandgap tuning applications but are quite challenging to realize through conventional techniques. We present the fabrication of large area and uniform square lattice based periodic nanostructures with 300 - 400 nm spatial periodicity on a GaAs substrate using pulsed laser interference. Single pulses from a plane-polarized pulsed laser working at 355 nm with 20-50 mJ energy and 7 ns pulse duration are used in a conventional four beam interference geometry at an incidence angle of 36.3˚ to realize square lattice patterns on photoresist coated over the GaAs substrate. The optical properties of the proposed designs are studied using FDTD simulations and show more than 95% of electromagnetic energy trapping over a broad optical wavelength range. This semiconductor based nanostructuring technology can find applications in improving the efficiency of solar cells or light emitting devices.