Band engineering with low-energy electron beam irradiation: Towards brighter scintillators

High-performance scintillators are essential for developing the emerging field of nano-scintillation. In this field, cathodoluminescence generated by electron beam interaction with scintillators can be controlled or enhanced by nanophotonic structures, making it valuable for medical imaging, radiative detection, and high-energy physics. Multiple-quantum-well (MQW) structures based on group III-nitride semiconductors are well-known scintillators for their flexibility in tuning the emission wavelength. Still, they suffer from low radiative efficiency due to the strong quantum-confined Stark effect (QCSE) and high defect density. In this work, we demonstrate a brighter AlGaInN MQW scintillator prepared using low-energy electron beam irradiation (LEEBI) for band engineering. LEEBI was successfully utilized for fabricating the first low-resist p-type GaN. By optimizing the energy and current, we achieved a two-order-of-magnitude increase in scintillation intensity without any shift in the emission peak. Furthermore, the carrier lifetime was counter-intuitively ten times longer. Using self-consistent calculations and cathodoluminescence characterization, we analyzed the LEEBI-induced band engineering mechanisms, including the control of QCSE and lateral carrier localization. We believe our findings will not only offer a deeper understanding and resolution to the long-standing contradictions surrounding LEEBI, but also push the boundaries of nanophotonic scintillation. The prominent enhancement of scintillation efficiency suggests new strategies for establishing ultra-low threshold electron-beam-pumped lasers, even in scanning electron microscopes, as a parallel counterpart to optically pumped lasers.