Periodic surface structure bifurcation induced by ultrafast laser generated point defect diffusion in GaAs
Michael J. AbereUniversity of Michigan 1 Department of Materials Science and Engineering, , Ann Arbor, Michigan 48109, USABen TorralvaUniversity of Michigan 2 Department of Atmospheric, Oceanic, and Space Sciences, , Ann Arbor, Michigan 48109, USAS. M. YalisoveUniversity of Michigan 1 Department of Materials Science and Engineering, , Ann Arbor, Michigan 48109, USA
2016en
ABI
Abstract
The formation of high spatial frequency laser induced periodic surface structures (HSFL) with period <0.3 λ in GaAs after irradiation with femtosecond laser pulses in air is studied. We have identified a point defect generation mechanism that operates in a specific range of fluences in semiconductors between the band-gap closure and ultrafast-melt thresholds that produces vacancy/interstitial pairs. Stress relaxation, via diffusing defects, forms the 350–400 nm tall and ∼90 nm wide structures through a bifurcation process of lower spatial frequency surface structures. The resulting HSFL are predominately epitaxial single crystals and retain the original GaAs stoichiometry.
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