GeSn Nanobeam Light-Emitting Diode as a GHz-Modulated Light Source

Designs and theoretical analysis are presented for a room temperature resonant-cavity-enhanced GeSn LED whose emission peaks at the 2 \mum wavelength. The Ge/GeSn/Ge PIN hetero-diode of length 1 \mum is embedded in a rib-type Ge-on-Si nanobeam having either 24 or 36 air holes. The maximum LED modulation bandwidth f_{3\text{dB}} is proportional to the Purcell factor and is inversely proportional to \tau _{s\,p0} the GeSn bulk spontaneous emission lifetime. For an emission linewidth of 200 nm and \tau _{s\,p0} of 10 ns, an f_{3\text{dB}} of 1.6 GHz is predicted.