Speaker
Description
Advances in InAs/GaAs semiconductor quantum dot (QD) heterostructures have enabled the development of an ultrafast, high light yield scintillator with a monolithically integrated photodetector, opening new possibilities for many applications including particle tracking. The QD scintillation detector (QDSD) combines rapid optical signal generation and collection with intrinsically suppressed Landau noise, addressing two fundamental factors that limit the timing performance of state-of-the-art silicon low gain avalanche detectors (LGADs). For QDSDs, where jitter is expected to be the dominant noise contribution, the time resolution is projected to surpass that of LGADs for tracker thicknesses above approximately 40 $\mu$m. Owing to the fast optical transport, the QDSD signal shape is not changing significantly with scintillator thickness. A thicker scintillator therefore produces a larger signal amplitude without adding electronic noise or the detector capacitance. Consequently, a time resolution of 10 ps or better may be achievable for MIPs in QDSDs thicker than approximately 120 $\mu$m, assuming near-unity detection efficiency; at 50% efficiency, approximately twice this thickness would be required. In alpha particle measurements, a time resolution (jitter) of 10 ps was achieved with a collected charge of 10 fC and improved to approximately 4 ps at 30 fC. The current challenges of QDSD technology are primarily the limited thickness of the epitaxial structure (20–30 $\mu$m) and the relatively low charge collection efficiency of 15%. The radiation hardness of QDSDs was evaluated using 1.5 MeV proton irradiation. With a GaAs barrier, the detector maintained its performance up to 3x10$^{12}$ protons/cm$^2$. Both the charge collection efficiency and radiation hardness can be improved by enhancing carrier localization within the QDs, either by increasing the barrier height or by lowering the operating temperature. Using a wider-bandgap AlGaAs barrier, the QDSD demonstrated radiation tolerance up to a proton fluence 10$^{14}$ protons/cm$^2$ at room temperature, corresponding to an equivalent 1 Mev neutron fluence of
2x10$^{15}$ cm$^{-2}$.