In this study, GaN/pSi heterojunction photodetectors were fabricated via pulsed laser deposition method (PLD). Photoelectrochemical etching method (PECE) with laser aid prepared a pSi substrate. Different laser wavelengths were tested on GaN and pSi films' structural, spectroscopic, electrical, and performance characteristics. XRD showed that GaN/pSi heterojunction photodetectors were polycrystalline and hexagonal. PL measurements showed two emission peaks attributable to GaN films (374, 364, 359 nm) and the pSi substrate (730, 729, 729 nm). Shorter laser wavelengths raised the GaN/pSi heterojunction's optical energy gap from 3.271 to 3.3415 eV. FESEM pictures showed that the average size of the manufactured samples was 51.88, 36.12, and 22.76 nm for spherical nanoparticles and a cauliflower-like shape. Atomic force microscopy (AFM) results show the root mean square of the surface roughness of prepared samples to be 4.83, 8.87, and 14.51 nm, respectively, as the laser wavelength became shorter with full coverage of all pores of prepared pSi. GaN/pSi heterojunction photodetectors had rectification in their dark I–V characteristics, and the heterojunction made at 355 nm had the best junction characteristics. The spectral responsivity of GaN/pSi photodetectors shows that the maximum responsivity was 29.01 A/W at 370 nm for a photodetector prepared at 355 nm. High detectivity and external quantum efficiency were 8.02×10+12 Jones and 359.73% at 370 nm, respectively. The photodetector fabricated using 355 nm showed a fast rise time of 328μsec and a fall time of 617μsec.
