Parameters of fast and high-yield InAs/GaAs quantum dot semiconductor scintillator

Abstract

InAs quantum dots (QDs) embedded into a waveguiding GaAs semiconductor matrix may produce scintillation detectors with exceptional speed and yield, making them valuable for nuclear security, medical imaging, and high-energy physics applications. In this work, we developed thick (~ 25 μm) epitaxial heterostructures with high luminescence efficiency composed of self-assembled nano-engineered InAs QDs grown by molecular beam epitaxy. The bulk GaAs acts as a stopping material for incident particles and as a waveguide when layer-transferred onto a low-index substrate. Waveguiding and self-absorption (< 1 cm−1) were studied using photoluminescence with scanning laser excitation and modeled with ray optics approximation and geometrical coupling of high-index waveguide to a collection fiber. Scintillating signals from α-particles were analyzed with an external photodiode (PD) and an integrated PD which provided an improved optical coupling. The mean charge collected by the integrated PD corresponded to 3 × 104 photoelectrons per 1 MeV of deposited energy or ~ 13% of the theoretically achievable light yield. Combined with the previously measured QD scintillation time of 0.3–0.6 ns, this makes the InAs/GaAs QD heterostructures the fastest high-yield scintillation material reported.