Thermally tunable Ge waveguide photodetector with a wide operating wavelength range

Area of Science:

• Photonics and Optoelectronics
• Semiconductor Devices
• Integrated Optics

Background:

• Germanium (Ge) photodetectors are crucial for optical communications.
• Extending detection to the L-band (1565–1625 nm) is essential for increased bandwidth.
• On-chip thermal tuning offers a compact solution for wavelength management.

Purpose of the Study:

• To design and fabricate a germanium waveguide p-i-n photodetector.
• To implement on-chip thermal tuning for extended wavelength detection.
• To characterize the device's performance, including responsivity and bandwidth.

Main Methods:

• Theoretical simulations were performed to predict thermal effects.
• A germanium waveguide p-i-n photodetector was fabricated.
• Experimental measurements were conducted to evaluate performance from 1525 to 1625 nm.
• Frequency response was measured to determine bandwidth.

Main Results:

• Thermal tuning with 3 V extended the detection range to the L-band.
• The photodetector operated effectively from 1525 to 1625 nm.
• A maximum responsivity of 0.72 A/W was achieved at 1625 nm.
• A 3 dB bandwidth exceeding 40 GHz was measured at -3 V.
• Higher tuning voltages increased dark current without significant absorption improvement.

Conclusions:

• The germanium waveguide photodetector with on-chip thermal tuning is effective for L-band operation.
• The device offers high responsivity and bandwidth suitable for optical communication systems.
• Optimizing thermal tuning is important to balance performance and dark current.