Epitaxial strain reconfiguration of AlGaN multiple heterojunctions for high-responsivity high-speed UV detection

Achieving simple and efficient strain engineering remains a persistent challenge in AlGaN-based material and device research, thereby substantially hampering the realization of the inherent material advantages. In this study, a strain reconfiguration strategy utilizing a medium-temperature AlN (MT-AlN) interlayer is proposed. By optimizing the MT-AlN thickness at 1000 °C, tensile strain originating from the GaN template is systematically released through interfacial relaxation and lattice redistribution within the interlayer. Additionally, the engineered configuration also establishes a coherent crystalline template with programmable strain states for subsequent epitaxial growth. With a 25-nm optimized interlayer, crack-free Al0.35 ∼ 0GaN multiple heterojunctions are epitaxially grown on the GaN template with slight compressive strain and nearly no additional dislocations. The resultant high-crystallinity AlGaN heterostructures enable the UV photodetector to achieve high responsivity (maximum 1.4 × 103 A/W), ultrafast response speed (0.6/25.4 ns rise/fall time), and remarkable operational stability simultaneously. All these collectively validate the MT-AlN strain reconfiguration as a viable pathway for the advancement of AlGaN-based optoelectronic devices.