Self-Powered MoTe2 Homojunction Photodetector with Ultrafast Response via h-BN Encapsulation and Doping Regulation

Abstract

Doping regulation can create spatial variations in carrier type or density by introducing different types or concentrations of impurities, forming stable p-n junction structures. This method maintains lattice continuity and minimizes interfacial defects, offering excellent controllability and process compatibility for large-area fabrication and integration applications. A semi-encapsulated MoTe₂ homojunction photodetector was fabricated by partially encapsulating with hexagonal boron nitride (h-BN) followed by high-temperature air annealing. The unencapsulated MoTe₂ region undergoes p-type doping from environmental H₂O and O₂ adsorption, while the encapsulated region remains ambipolar due to environmental isolation. The resultant Fermi level gradient generated an intrinsic electric field at the junction, enhancing photovoltaic performance with improved responsivity (21 mA/W) and accelerated response speed (54.6/55.2 μs). At a gate voltage (V_gs) of 40 V, the device exhibited a rectification ratio of 2.2 × 10³ and a specific detectivity of 1 × 10¹¹ Jones. This work demonstrates an environmentally modulated doping strategy for self-powered photodetectors with ultrafast temporal response and defect-minimized interfaces.