CMOS tunable-wavelength multi-color photogate sensor.

Area of Science:

• Integrated photonics
• Optoelectronics
• Semiconductor device physics

Background:

• Traditional multi-color sensing often requires bulky external filters.
• Developing compact, on-chip spectral filtering solutions is crucial for miniaturization.
• CMOS technology offers a scalable platform for integrated optical sensors.

Purpose of the Study:

• To present a CMOS tunable-wavelength multi-color photogate (CPG) sensor.
• To demonstrate on-chip spectral filtering capabilities by tuning the polysilicon gate.
• To validate the sensor's performance in light intensity and quantum dot fluorescence detection.

Main Methods:

• Fabrication of a CPG sensor prototype using standard 0.35 μm digital CMOS technology.
• Tuning the spectral response of the CPG sensor via applied bias voltage.
• Characterization of the sensor's performance using blue, green, and red light sources and quantum dots.

Main Results:

• The CPG sensor successfully measured blue (450 nm), green (520 nm), and red (620 nm) light with high peak SNRs (34.7 dB, 29.2 dB, 34.8 dB).
• The prototype achieved on-chip spectral differentiation for fluorescence detection of green-emitting quantum dots (gQDs) and red-emitting quantum dots (rQDs).
• Detection limits were established at 24 nM for single-color QD measurements and 90 nM (gQD) / 120 nM (rQD) for multi-color measurements.

Conclusions:

• The CPG sensor effectively integrates spectral filtering and sensing onto a single chip, eliminating the need for external filters.
• The tunable wavelength capability allows for selective sensing of well-separated wavelengths (> 50 nm apart).
• The demonstrated performance in light and QD detection highlights the potential of CPG sensors for various applications, including bio-imaging and environmental monitoring.