Investigation of Optoelectronic Properties in Germanium Nanowire Integrated Silicon Substrate Using Kelvin Probe Force Microscopy

Catalyst free Germanium (Ge) nanowires (NW) and thin film (TF) have been synthesized by employing GLAD technique inside an electron-beam evaporator. X-ray diffraction patterns confirmed the successful growth of polycrystalline Ge-NW and Ge-TF. The FEG-SEM image revealed the growth of highly oriented vertical nanowires with an average length of ~110 nm and a diameter of ~48 nm. The optical absorption of Ge-NW showed enhancement over the Ge-TF. The blue shift observed in optical absorption for the NW and TF samples is due to the quantum confinement. The work function is computed using Kelvin probe force microscopy (KPFM) for Ge-NW (~4.11 eV) and Ge-TF (~4.18 eV) samples. The current density for Ge-TF and Ge-NW, when exposed to light, is ~0.85 mA/cm2and ~6.95 mA/cm2at 5 V bias, respectively. Ag/Ge-NW/n-Si device exhibits maximum photosensitivity of 35 times compared to the Ge-TF device at -5.5 V. Additionally, better switching is observed for Ge-NW device compared to Ge-TF device, which is a good candidate for photodetector application.