Subwavelength Antireflection Gratings for Light Emitting Diodes and Photodiodes Fabricated by Fast Atom Beam Etching

A two-dimensional antireflection subwavelangth-structured (SWS) surface is fabricated on GaAlAs light-emitting diodes (LEDs) and photodiodes. The SWS is patterned by electron beam lithography and etched by fast atom beams of SF 6 and Cl 2 gases. The SWS grating has a conical profile, 200 nm period and 270 nm groove depth. The emission intensity from this LED is 30% larger than that from the LED without a SWS grating at the peak emission wavelength. When this device is used as a photodiode, the reflection reduced by the SWS surface increases both the short-circuit current and open-circuit voltage. The SWS surface is useful as an antireflection structure improving the efficiency of the light emission of LEDs and the light detection of photodiodes.