Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

• Published in: Instruments (Basel) Vol. 5; no. 2; p. 17
• Main Authors: Lee, Eldred, Anagnost, Kaitlin M., Wang, Zhehui, James, Michael R., Fossum, Eric R., Liu, Jifeng
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 30.04.2021
• Subjects: Attenuation; Charge coupled devices; CMOS; compound semiconductors; Design; Efficiency; Energy; High resolution; Image enhancement; Inelastic scattering; Light; materials science; Monte Carlo simulation; multidisciplinary; Photoelectricity; Photoelectrons; photonics; Photons; Response time; semiconductors; Sensors; Spatial resolution; X ray detectors; X-ray detection; X-rays
• ISSN: 2410-390X; 2410-390X
• DOI: 10.3390/instruments5020017

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.