Broadband synaptic photoresponse induced by the charged planar Te interlayer in epitaxial Te/GaN hybrid-heterojunction

Broadband photodetection is crucial for a variety of advanced sensing applications like environmental monitoring, optical communication, and optoelectronic synapses. The emerging van der Waals (vdW) optoelectronic materials become important complementary to the conventional semiconductors, which are mostly optimized for specific spectral ranges. In this work, we report a new strategy to realize broadband synaptic photoresponse by growing the vdW material Te on III-V semiconductor GaN as an epitaxial hybrid-heterojunction that contains a functional charged planar Te interlayer. Apart from the combined wide-bandgap of GaN and the narrow-bandgap of tellurium, the photoresponse of the heterojunction is also boosted by the charged planar Te interlayer due to the polarization charge on GaN surface, giving rise to a broadband light detection across the ultraviolet-infrared (UV-IR) spectrum (200–2500 nm). The samples are grown by physical vapor deposition (PVD), while the devices are fabricated by a shadow-mask-assisted electrode deposition technique, both in ultra-high vacuum (UHV) environment. The optoelectronic transport measurements confirm the self-powered broadband photodetection and synaptic behavior of paired-pulse facilitation (PPF). First-principles calculations reveal that the interfacial planar Te interlayer combined with spontaneous polarization of GaN modulated the electronic properties of the heterojunction, affecting carrier dynamics under light illumination. This work paves the way for the development of advanced photodetectors with applications in optoelectronics and neuromorphic computing.