Broadband antirefraction property is demonstrated by using subwavelength grating structures on GaSb wafers, which are the base material of GaSb PV cells. Surface nano-structure with 350nm periods is fabricated by means of electron beam lithography and fast atom beam (FAB) etching. Since FAB is electrically neutral atomic or molecular beam, it is possible to obtain fine patterns with nanometer order. The reflectivity of this sample is strongly suppressed from the visible to near IR region. The experimental data is compared with numerical simulations by using the rigorous coupled wave analysis. The thermal stability of SWG structures are also studied by measuring reflection spectra of heated samples.
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