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

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Germanium (Ge) quantum dots are promising for infrared photodetection.
• Silicon-Germanium (SiGe) alloys offer tunable bandgaps for optoelectronic devices.
• Enhancing infrared detector sensitivity and responsivity remains a key challenge.

Purpose of the Study:

• To fabricate and characterize a multilayer Ge quantum dot detector on a SiGe virtual substrate for mid-wave infrared (MWIR) photodetection.
• To investigate the role of SiGe barriers in enhancing photovoltaic response.
• To explore the impact of surface plasmon polariton (SPP) excitation using a 2D plasmonic structure on detector sensitivity.

Main Methods:

• Fabrication of multilayer Ge quantum dots on a Si1-xGex (x=0.18) virtual substrate.
• Characterization of photovoltaic response and responsivity.
• Integration with a 2D plasmonic structure to excite SPPs.
• Measurement of detector performance under MWIR illumination at 90 K and zero bias.

Main Results:

• The Ge quantum dot detector on SiGe exhibited over 100% enhanced photovoltaic response compared to conventional Ge/Si devices.
• The smaller hole effective mass in SiGe barriers contributed to the enhanced response.
• Coupling with a 2D plasmonic structure significantly improved sensitivity via SPP excitation.
• Enhanced photocurrent was observed when illumination was from the substrate side.
• At 90 K and zero bias, responsivity reached 40 mA/W and peak detectivity was 1.4 × 10^11 cm·Hz^1/2/W at 4 µm.

Conclusions:

• Multilayer Ge quantum dots on SiGe virtual substrates are effective for MWIR photodetection.
• SiGe barriers play a crucial role in enhancing photovoltaic performance.
• Plasmonic structures offer a viable route to further boost the sensitivity of Ge-based infrared detectors.
• The developed detector shows high performance metrics suitable for advanced infrared imaging applications.