Waveguide-integrated microdisk light-emitting diode and photodetector based on Ge quantum dots

Area of Science:

• Optoelectronics
• Quantum Dot Technology
• Integrated Photonics

Background:

• Silicon-on-insulator (SOI) platforms are crucial for integrated photonics.
• Germanium (Ge) quantum dots offer tunable optoelectronic properties.
• Microdisk resonators enable wavelength-selective light-matter interactions.

Purpose of the Study:

• To fabricate and characterize a novel microdisk device integrated with a bus waveguide.
• To utilize Ge self-assembled quantum dots as the active medium for light emission and detection.
• To demonstrate the dual functionality of the device as a light-emitting diode (LED) and a photodetector.

Main Methods:

• Fabrication of a microdisk resonator on an SOI substrate.
• Integration of Ge self-assembled quantum dots within the microdisk.
• Characterization of electroluminescence and photo-response under varying bias conditions.
• Analysis of whispering gallery modes and resonant cavity enhancement.

Main Results:

• The device operated as an LED, emitting light at 1.45-1.6 μm with sharp resonant peaks (Q-factor up to 1350) due to whispering gallery modes.
• As a photodetector, it exhibited wavelength-selective photo-response, with photocurrent 50 times larger at resonance.
• Achieved low dark current density (0.29 mA/cm²) and a peak responsivity of 5.645 mA/W.

Conclusions:

• The integrated microdisk device with Ge quantum dots successfully functions as both an LED and a photodetector.
• Whispering gallery modes enhance both light emission efficiency and photodetector sensitivity.
• This demonstrates a promising platform for on-chip optical communication and sensing applications.