"Extending the wavelength response of photon-counting image sensors"

Abstract

Non-visible imaging is used in a variety of applications, including medical imaging, security, astronomy, light detection and ranging (LiDAR), and more. Typical silicon-based detectors are primarily limited to the visible spectral regime, with weak responses to ultraviolet and infrared (IR) light. To improve the sensor’s quantum efficiency for x-rays, for example, a scintillating layer may be deposited at the cost of decreased spatial resolution. State-of-the-art IR detectors, on the other hand, use HgCdTe in favor of silicon, increasing cost and decreasing long-term reliability.

Silicon-based detectors with photon conversion layers are presented in this thesis as possible alternatives to extend the wavelength response in the x-ray and IR spectral regimes. For better x-ray sensitivity, a photon attenuation layer (PAL) to mitigate the quantum efficiency vs. spatial resolution trade-off present in typical scintillators is described. GeSn is considered for deposition on silicon for an IR detector. To prevent the pixel’s transfer gate from losing functionality due to the deposition process, a 3-T pixel with a noise-cancelling feedback amplifier is discussed.

Expanding upon the IR modeling work and designing a Quanta Image Sensor (QIS) pixel for LiDAR applications is proposed. The band structures for GeSn and various III-V materials on silicon will be calculated and compared to find the ideal IR absorber. Next, LiDAR is considered as a potential application for this IR absorbing layer. A QIS pixel will be designed with improved timing resolution while maintaining lower power dissipation compared to single photon avalanche diodes (SPADs) for LiDAR devices.

Thesis Committee

• Prof. Fossum, chair
• Prof. Liu
• Prof. Odame

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.