GaN-Based Ultraviolet Passive Pixel Sensor on Silicon (111) Substrate.

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Conventional Gallium Nitride (GaN)-based ultraviolet (UV) imaging devices often rely on hybrid integration, involving complex backside substrate etching and wafer-to-wafer bonding.
• Developing efficient single-pixel sensors is crucial for fabricating advanced array-type pixel sensors.

Purpose of the Study:

• To develop a GaN-based UV passive pixel sensor (PPS) utilizing a monolithic integration technique.
• To demonstrate the integration of a GaN metal-semiconductor-metal (MSM) UV photodetector and a Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET).

Main Methods:

• Monolithic integration of a GaN MSM UV photodetector and a GaN SB-MOSFET on an epitaxially grown GaN layer on a silicon substrate.
• Characterization of the fabricated MSM UV sensor for dark current density and UV/visible rejection ratio.
• Evaluation of the GaN SB-MOSFET performance, including drain current, transconductance, and threshold voltage.
• Testing the UV PPS response and dark-to-photo contrast ratio under 365-nm UV irradiation.

Main Results:

• The integrated GaN MSM UV sensor achieved a low dark current density of 3.3 × 10^-7 A/cm² and a high UV/visible rejection ratio of 10³.
• The GaN SB-MOSFET demonstrated normally-off operation with a maximum drain current of 0.5 mA/mm, maximum transconductance of 30 μS/mm, and a threshold voltage of 4.5 V.
• The developed UV PPS exhibited good UV response and a high dark-to-photo contrast ratio of 10³.

Conclusions:

• The developed monolithic integration technique successfully combined a GaN UV photodetector and a GaN SB-MOSFET on a silicon substrate.
• This approach offers a viable method for the monolithic integration of GaN-based optoelectronic devices, potentially simplifying fabrication processes.
• The demonstrated performance metrics indicate the potential of this integrated device for UV imaging applications.