Preparation of Nanostructured HgI2 Nanotubes/Si Photodetector by Laser Ablation in Liquid

In this study, we present a high-performance HgI2 nanotubes/Si heterojunction photodetector by a simple one-step pulsed laser ablation in ethanol at a laser fluence of 12.7 J/cm(2). The structural and optical properties of HgI2 nanotubes (NTs) are studied. The X-ray diffraction (XRD) measurement shows the presence of the mixture of tetragonal and orthorhombic phases of HgI2. The optical properties results show that the optical energy gap of HgI2 NTs was 2.98 eV measured at room temperature. The photoluminescence (PL) spectrum of HgI2 displays a single emission centered at 535 nm. Scanning electron microscope (SEM) image show the formation of nanotubes and spherical nanoparticles with an average particle size of 23 nm. The transmission electron microscope (TEM) image of HgI2 confirms the formation of nanotubes morphology with an average diameter of 80 nm and an average length of 1.6 mu m. The current-voltage characteristics of HgI2 NTs/p-Si heterojunction were measured at dark and illumination. The HgI2 nanotubes/Si photodetector is sensitive to the spectral region ranging from visible to near infrared region. This photodetector presents a responsivity of up-to 1.09 A/W at 450 nm under an external bias voltage of 5 V. The specific detectivity (D*) and external quantum efficiency (EQE) of the photodetector are 3.6 x 10(12) Jones and 3 x 10(2)% at 400 nm, respectively, without using post annealing. The fabricated photodetector has good linearity characteristics with a large linear dynamic region, and the saturation in photocurrent is observed at 180 mW/cm(2). The figures of merit of the fabricated photodetector are compared with those of some heterojunction-based silicon photodetectors.