Photovoltaic Ge/SiGe quantum dot mid-infrared photodetector enhanced by surface plasmons

We report the fabrication and characterization of a multilayer Ge quantum dot detector grown on Si_1-xGex virtual substrate (x = 0.18) for photovoltaic mid-wave infrared photodetection. Detector displays an over 100% photovoltaic response enhancement as compared to a conventional Ge/Si device due to smaller hole effective mass in the SiGe barriers. A further enhancement in sensitivity is achieved by excitation of surface plasmon polariton waves in a Ge/SiGe photodetector coupled with a two-dimensional plasmonic structure. The plasmonic resonance induced photocurrent enhancement is found to be larger when the incident infrared light illuminates the detector from its substrate side. At zero bias and 90 K, the responsivity of 40 mA/W and peak detectivity of 1.4 × 10¹¹ cm·Hz^1/2/W are determined at a wavelength of 4 µm.