Unveiling the Hot Carrier Distribution in Vertical Graphene/h-BN/Au van der Waals Heterostructures for High-Performance Photodetector

Abstract

Graphene is one of the most promising materials for photodetectors due to its ability to convert photons into hot carriers within approximately 50 fs and generate long-lived thermalized states with lifetimes longer than 1 ps. In this study, we demonstrate a wide range of vertical photodetectors having a graphene/h-BN/Au heterostructure in which an hexagonal boron nitride (h-BN) insulating layer is inserted between an Au electrode and graphene photoabsorber. The photocarriers effectively tunnel through the small hole barrier (1.93 eV) at the Au/h-BN junction while the dark carriers are highly suppressed by a large electron barrier (2.27 eV) at the graphene/h-BN junction. Thus, an extremely low dark current of ∼10 −13 A is achieved, which is 8 orders of magnitude lower than that of graphene lateral photodetector devices (∼10 −5 A). Also, our device displays an asymmetric photoresponse behavior due to photothermionic emission at the graphene/h-BN and Au/h-BN junctions. The asymmetric behavior generates additional thermal carriers (hot carriers) to enable our device to generate photocurrents that can overcome the Schottky barrier. Furthermore, our device shows the highest value of the I ph /I dark ratio of ∼225 at 7 nm thick h-BN insulating layer, which is 3 orders of magnitude larger than that of the previously reported graphene lateral photodetectors without any active materials. In addition, we achieve a fast response speed of 12 μs of rise time and 5 μs of fall time, which are about 100 times faster than those of other graphene integrated photodetectors.

Bioprinting of Collagen: Considerations, Potentials, and Applications

“…Properties of collagen bioink can be tuned through either blending with thickening agents (e.g., alginate, [ 182,198,203 ] agarose, [ 199,203 ] Pluronic, [ 204 ] fibrin, [ 181,183,188 ] and hyaluronic acid [ 186 ] ) or inducing semi‐crosslinked mixture prior to printing (e.g., thermal, [ 204 ] pH neutralize, [ 199 ] crosslinker [ 191 ] ). These techniques have been commonly used for extrusion‐based bioprinting, where bioink with higher viscosity is preferred.…”

An InGaN/SiNx/Si Uniband Diode Photodetector

“…In contrast, the band offsets for 2D materials can freely adjust due to the van der Waals bonds at the interfaces. [15,[26][27][28][29] Under illumination, the I-V curves with logarithmic current scale for the InGaN/SiN x /Si uniband diode PD are shown in Figure 3a for different wavelengths of the incident light: 808, 638, 532, and 405 nm and 10 mW cm À2 excitation power density. The I-V curves with reduced linear scales around zero are shown in the inset.…”

“…In contrast, the band offsets for 2D materials can freely adjust due to the van der Waals bonds at the interfaces. [ 15,26–29 ]…”

Bioprinting a cell‐laden matrix for bone regeneration: A focused review

“…However, the light emission during the cross‐linking reduced the number of viable cells, while no adverse effect was observed through the changes in pH. In a novel study by Kim et al, 110 an osteoblast‐like cell and human adipose stem cells‐laden matrix composed of cross‐linked collagen mimicked the natural tissue structure. Accordingly, the cross‐linking via genipin (1 mM) for approximately 1 h and bioprinting conditions did not affect cell viability since the results of the analysis indicating more than 95% viable cells.…”