Investigation on the Isolation Approaches for High-Voltage GaN-on-Sapphire Monolithic Power Integrated Circuits

Area of Science:

• Materials Science
• Semiconductor Physics
• Electrical Engineering

Background:

• Gallium Nitride (GaN) on insulated sapphire substrates enable higher rated voltages for monolithic power integrated circuits (MPICs) compared to silicon substrates.
• Investigating isolation techniques is crucial for optimizing performance and stability in GaN-on-Sapphire MPICs.

Purpose of the Study:

• To evaluate the effectiveness of isolation approaches in GaN-on-Sapphire MPICs, focusing on substrate bias and crosstalk effects.
• To analyze the impact of ion implantation and shallow trench isolation on device performance and stability.

Main Methods:

• Fabrication of GaN-on-Sapphire MPICs with ion implantation isolation.
• Analysis of substrate bias and crosstalk effects between adjacent high-side and low-side power devices.
• Implementation and evaluation of shallow trench isolation (STI) to mitigate crosstalk.

Main Results:

• Ion implantation effectively suppresses substrate bias and crosstalk between power devices, irrespective of substrate termination.
• Ion implantation isolates adjacent high-voltage and low-voltage devices, though a minor crosstalk (up to 3% degradation) due to capacitive coupling is observed.
• Shallow trench isolation within the implantation region significantly mitigates crosstalk between high-voltage and low-voltage devices.

Conclusions:

• Ion implantation is a viable isolation approach for GaN-on-Sapphire MPICs, reducing parasitic effects.
• Shallow trench isolation is recommended to further enhance the stability of integrated logic circuits and drivers during high-voltage switching.