One-dimensional antireflection gratings in (100) silicon: A numerical study

The antireflection properties of V-grooved gratings in (100) crystalline silicon are studied numerically by use of rigorous electromagnetic theory. This study shows that these gratings can exhibit antireflective behavior only for TM-polarized radiation. The V-grooved structures are analyzed as a function of grating period, duty cycle, and depth of a SiO₂ mask layer that is added to the tops of the V-grooved mesas. Specific antireflection grating designs (the duty cycle and depth versus the period) are presented that illustrate TM-polarized reflectivity much less than 10⁻³ with periods as high as 80% the wavelength of incident radiation. These designs exhibit good tolerance to fabrication errors and grating’s plane deviations in a planar-diffraction mounting.