Si/Ge phototransistor with responsivity >1000A/W on a silicon photonics platform

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Phototransistors are crucial components in optical communication systems.
• Existing designs often face limitations in responsivity and dark current under low bias.
• Efficient light detection requires optimized device structures and electric field engineering.

Purpose of the Study:

• To develop a Si/Ge waveguide phototransistor with enhanced performance.
• To investigate the impact of engineered electric field distribution on device characteristics.
• To achieve high responsivity and low dark current at low operating voltages.

Main Methods:

• Fabrication of a Si/Ge waveguide phototransistor utilizing n-i-p-i-n doping.
• Integration of two p+-doped regions within the silicon slab beneath the Ge epitaxial layer.
• Characterization of responsivity, dark current, bandwidth, and phase noise under varying bias conditions.

Main Results:

• Achieved responsivity of 606 A/W at 1 V bias and 1032 A/W at 2.8 V bias for -50 dBm input optical power.
• Demonstrated low dark current of 4 µA at 1 V and 42 µA at 2.8 V.
• Measured a small signal -3 dB bandwidth of 1.5 GHz and phase noise of -80 dBc/Hz at 1 KHz offset.

Conclusions:

• The engineered electric field distribution significantly enhances phototransistor performance.
• The developed Si/Ge waveguide phototransistor offers high responsivity and low dark current.
• This device shows potential for advanced optoelectronic applications requiring efficient light detection.