An Ultraviolet Sensor and Indicator Module Based on p-i-n Photodiodes

Area of Science:

• Optoelectronics
• Semiconductor Devices
• UV Sensing Technology

Background:

• Hybrid UV sensor and warning lamp systems are bulky and expensive.
• Monolithic integration offers advantages in size, cost, and performance.

Purpose of the Study:

• To develop a cost-effective, monolithic module integrating an ultraviolet (UV) sensor and a warning lamp.
• To demonstrate the feasibility of simultaneous fabrication of Gallium Nitride (GaN)-based light-emitting diodes (LEDs) and p-i-n (PIN) photodiodes.
• To evaluate the performance of the integrated UV sensor indicator device.

Main Methods:

• Fabrication of GaN-based LEDs with an indium-tin oxide (ITO) layer and PIN photodiodes without ITO.
• Simultaneous fabrication of both photodiodes and LEDs on a single substrate.
• Characterization of photodiodes' responsivity at UV wavelengths (381 nm and 350 nm) under a 5 V bias.
• Measurement of photocurrent-to-voltage conversion and LED driving.
• Analysis of epitaxial structural effects on photocurrent collection efficiency.
• Assessment of crosstalk between PIN photodiodes and LEDs.

Main Results:

• Achieved significantly higher incident photon-to-electron conversion efficiencies in PIN photodiodes compared to reverse-biased LEDs at UV wavelengths.
• Demonstrated responsivities of 0.20 A/W at 381 nm and 0.16 A/W at 350 nm with a 5 V bias.
• Developed a functional indicator where LED brightness correlates with ambient UV intensity.
• Identified epitaxial structural factors influencing UV photocurrent collection.
• Quantified crosstalk between photodiodes and LEDs at varying distances.

Conclusions:

• Monolithic integration of UV sensors and warning lamps is feasible and advantageous over hybrid systems.
• The developed GaN-based PIN photodiode and LED module offers efficient UV detection and indication.
• Optimizing epitaxial structures is crucial for maximizing UV sensing performance.
• The device shows potential for cost-effective UV monitoring applications.