Fig. 1: Schematic illustration of the germanium/perovskite heterojunction device fabrication process.

a A cleaned SiO2/Si substrate. b A germanium layer growth by MBE. c Au electrode deposition on the substrate. d Perovskite layer construction by the vapor-solution method. e Three-dimensional diagram of the heterojunction photodetector. f Top-view and g cross-sectional SEM image of the achieved heterostructure device (scale bar = 200 nm). h Steady-state photoluminescence spectrum of the constructed perovskite film.