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.