PtSe₂-Based Heterostructures on GaP Nanowires: Interface Formation and Photoelectrical Properties

PtSe₂/GaP nanowire heterostructures were fabricated and characterized to explore their optoelectronic response under broadband illumination. Few-layer PtSe₂ was synthesized on GaP substrates with and without nanowires by selenization of a pre-deposited Pt layer. Such PtSe₂/III-V heterostructures are attractive for next-generation photodetectors because they combine the tunable band structure and environmental stability of PtSe₂ with the wide bandgap and established epitaxial technology of GaP. Structural and spectroscopic characterization confirms the formation of PtSe₂ and reveals pronounced interfacial reactions between GaP and the chalcogen/metal layers. Cross-sectional STEM and compositional analysis show a heterogeneous interface comprising a PtSe₂-rich top region containing embedded Ga₂Se₃ crystallites and an underlying predominantly amorphous Ga₂O₃-rich interlayer on GaP. Optical measurements reveal absorption edges in the 1.4-1.7 eV range attributed to PtSe₂ and a higher-energy edge around 2.6 eV associated with GaP. Two-terminal current-voltage measurements in the dark and under illumination exhibit rectifying, photodiode-like behavior with a broadband photoresponse arising from both GaP and PtSe₂. These results demonstrate that PtSe₂-rich/Ga₂O₃-rich/GaP heterostructures containing Ga₂Se₃ crystallites obtained by selenization of thin Pt layers on GaP provide a simple route to photoactive interfaces combining two-dimensional chalcogenides with III-V semiconductors.