GeSn lateral p-i-n waveguide photodetectors for mid-infrared integrated photonics
Cheng-Hsun Tsai, Kuan-Chih Lin, Chin-Yuan Cheng, Kuo-Chih Lee, Hung-Hsiang Cheng, Guo‐En Chang
Abstract
In this Letter, we demonstrate mid-infrared (MIR) lateral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>−</mml:mo></mml:mrow><mml:mi>i</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>−</mml:mo></mml:mrow><mml:mi>n</mml:mi></mml:math> GeSn waveguide photodetectors (WGPDs) on silicon, to the best of our knowledge for the first time, as a key enabler of MIR electronic–photonic integrated circuits (EPICs). Narrow-bandgap GeSn alloys were employed as the active material to enable efficient photodetection in the MIR region. A lateral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>−</mml:mo></mml:mrow><mml:mi>i</mml:mi><mml:mrow class="MJX-TeXAtom-ORD"><mml:mo>−</mml:mo></mml:mrow><mml:mi>n</mml:mi></mml:math> homojunction diode was designed and fabricated to significantly enhance the optical confinement factor of the guided modes and thus enhance the optical responsivity. Thus, a photodetection range of up to 1950 nm and a good responsivity of 0.292 A/W at 1800 nm were achieved. These results demonstrate the feasibility of planar GeSn WGPDs for monolithic MIR EPICs on silicon.