Abstract
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/cm2. 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 μm. 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 × 1012 Jones and 3 × 102% 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/cm2. The figures of merit of the fabricated photodetector are compared with those of some heterojunction-based silicon photodetectors.
Highlights
Mercury iodide is a semiconducting material with energy gap as larger as 2.13 eV at room temperature
The optical properties results show that the optical energy gap of HgI2 NTs was 2.98 eV measured at room temperature
(214) plans are belong to orthorhombic β-HgI2 according to JCPDS-ICDD #15-0034, while (101) and (102) plans are indexed to tetragonal α-HgI2 [7,10], indicating that the synthesized HgI2 NTs are mixture of two phases α-HgI2 and β-HgI2
Summary
Mercury iodide is a semiconducting material with energy gap as larger as 2.13 eV at room temperature. Its tunable energy gap is one of the most important property that enables HgI2 to be used significantly for optoelectronic devices. This manipulation in energy gap can be obtained via changing the particle size. Many techniques were employed to prepare nanostructure HgI2 for instance rapid co-precipitation, spray pyrolysis, laser deposition, and hydrothermal [6,7,8]. Few papers were reported on the preparation and characterization of nanostructured HgI2. High responsivity HgI2 nanorods/Si heterojunction photodetector was fabricated using pulsed laser deposition technique [8]. We report on synthesis HgI2 nanotubes for the first time via pulsed laser ablation in liquid. Fabrication and characterization of HgI2 NTs /Si heterojunction photodetector without using buffer layer were demonstrated
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