Optical properties of InAs quantum Dots/GaAs waveguides for ultra-fast scintillators

Abstract InAs Quantum Dots (QDs) embedded in a GaAs matrix have unique scintillation properties, valuable for high-energy physics and medical applications. Temperature-dependent photoluminescence, waveguide attenuation and alpha particle response measurements were employed to analyze the optical properties of a 25 μm thick waveguiding scintillator. Optimizing the electrostatics of the QD layered structure with p-type modulation doping resulted in QD photoluminescence (PL) efficiency as high as 60% at room temperature. Analysis of attenuation of the QD waveguide showed surface scattering predominated over the first 2–3 mm of light propagation and low (∼1 cm−1) self-absorption was more significant at longer distances, after the after the decay of high order modes (high angle light rays). Responses to 5.5 MeV alpha particles from the integrated photodiode on top of the QD scintillator/waveguide (QD/WG) show an extremely fast (300 ps) decay constant, and a 70 ps time resolution (limited by circuit noise and bandwidth) with a collection efficiency of 17,000 photons per 1 MeV of deposited energy.