Enhanced Performance of Single-Walled Carbon Nanotube-Germanium Near-Infrared Photodetector by Doping with Au Nanoparticles

Abstract

This paper presents a near-infrared (near-IR) photodetector based on a gold nanoparticles-doped (AuNPs-doped), single-walled carbon nanotube–germanium (SWCNT/Ge) heterojunction. The responsivity, detectivity, and response time of the AuNPs-doped, SWCNT/Ge heterojunction photodetector measured 476 mA W−1 (a 291% improvement), 1.0 × 1012 cm Hz1/2 W−1 (a 208% improvement), and 8 μs, respectively. The mechanism of the enhanced performance originated from the surface modification by gold doping, which effectively improved the work function of the carbon nanotube films and thus increased the barrier height between the heterojunctions, as measured by the contact potential distribution (CPD) and open circuit voltage (Voc) of the SWCNT/Ge interface. In addition, we investigated the effect of various particle sizes on the performance and stability of the photodetector. The results demonstrate the promising prospects of the presented heterojunction photodetector for infrared detection applications.

Photoresponse of Carbon Nanofiber-Based Photodetector and Its Enhancement on CuNi Nanoparticle Adsorption

“…The enhanced responsivities in the 600–800 nm region are likely to arise due to the absorption edge of the silicon substrate . The midrange minima (0.1 to 0.3 A/W) in the spectra are also considerably moderate and match well with previous reports. , The maximum responsivity is higher than the previously reported values for CNT/Si heterojunction photodetectors. ,, This itself suggests that CNF-based photodetectors have the potential to show a better photoresponse than CNT-based photodetectors.…”

“…The smaller BE F value for the CN-CNF sample suggests that its ϕ is larger by 0.6 eV than that of the CNF sample . This ϕ enhancement is in agreement with the report by Qi et al, where the work function of CNTs increases on decorating them with Au NPs. Changes in the work function of a surface are caused essentially by any charge transfer to (or from) an adsorbate, and the associated surface dipole. − In general, the sign of the change depends on the relative electronegativity of the adsorbate: the work function decreases when the adsorbate is less electronegative and vice versa. , This way, since the (common) electronegativity of the adsorbate atoms Cu and Ni is less than that of the C atoms on the CNF surface, the CNF work function should decrease.…”

“…Thus, the CN-CNF/Si device has switching properties much better than those of the CNF/Si device. As the CN-CNF/Si device has a larger built-in potential and hence a larger electric field across the depletion region, the photogenerated carriers are more quickly swept away on removal of the light, leading to a shorter decay time …”

“…This necessitates the development of low cost, preferably high-performance, and broadband photodetectors. Carbon nanotubes (CNTs), which have adjustable band gaps and hence broadband absorption, have emerged rapidly as an essential component of photodetectors. − Photodetectors based on heterostructures of single- and multiwalled CNTs (SWCNTs and MWCNTs) and Si, Ge, SiO 2 or GaAs have been studied for photodetection in optical and near-infrared spectral ranges. ,,− However, CNTs come with their own limitations, like moderate thermal stability and mechanical strength, ,, making it desirable to search for materials that can provide improved photodetection properties on one hand and better thermal and mechanical stability on the other. In this regard, carbon nanofibers (CNFs) could be a suitable alternative to CNTs, because, along with showing similar optical properties, , they possess a larger specific surface area that could be beneficially utilized for photocarrier generation and are cheaper and easier to produce. ,, The large active surface area and excellent conductivity of CNFs have recently been utilized by combining CNFs with biomolecules, polymers, and inorganic substances.…”

“… 11 − 14 Photodetectors based on heterostructures of single- and multiwalled CNTs (SWCNTs and MWCNTs) and Si, Ge, SiO 2 or GaAs have been studied for photodetection in optical and near-infrared spectral ranges. 1 , 10 , 15 − 19 However, CNTs come with their own limitations, like moderate thermal stability and mechanical strength, 13 , 16 , 20 making it desirable to search for materials that can provide improved photodetection properties on one hand and better thermal and mechanical stability on the other. In this regard, carbon nanofibers (CNFs) could be a suitable alternative to CNTs, because, along with showing similar optical properties, 13 , 21 they possess a larger specific surface area that could be beneficially utilized for photocarrier generation and are cheaper and easier to produce.…”