High‐Gain 200 ns Photodetectors from Self‐Aligned CdS–CdSe Core–Shell Nanowalls

Abstract

1D core-shell heterojunction nanostructures have great potential for high-performance, compact optoelectronic devices owing to their high interface area to volume ratio, yet their bottom-up assembly toward scalable fabrication remains a challenge. Here the site-controlled growth of aligned CdS-CdSe core-shell nanowalls is reported by a combination of surface-guided vapor-liquid-solid horizontal growth and selective-area vapor-solid epitaxial growth, and their integration into photodetectors at wafer-scale without postgrowth transfer, alignment, or selective shell-etching steps. The photocurrent response of these nanowalls is reduced to 200 ns with a gain of up to 3.8 × 10 and a photoresponsivity of 1.2 × 10 A W , the fastest response at such a high gain ever reported for photodetectors based on compound semiconductor nanostructures. The simultaneous achievement of sub-microsecond response and high-gain photocurrent is attributed to the virtues of both the epitaxial CdS-CdSe heterojunction and the enhanced charge-separation efficiency of the core-shell nanowall geometry. Surface-guided nanostructures are promising templates for wafer-scale fabrication of self-aligned core-shell nanostructures toward scalable fabrication of high-performance compact photodetectors from the bottom-up.

Plasmonic Photonic Crystals Induced Two‐Order Fluorescence Enhancement of Blue Perovskite Nanocrystals and Its Application for High‐Performance Flexible Ultraviolet Photodetectors

“…Figure b presents the photocurrent–time ( I – t ) response curves of with and without plasmon photonic crystals in the dark ( I dark ) and under 365 nm illumination ( I ph , 10 mW cm −2 ) at a bias of 3 V. The dark current for the two detectors is particularly low, in the order of 10 –2 nA. The photosensitivity ( P *), which is defined as the ratio of photocurrent to dark current (On/off ratio: I ph / I dark ), was exceedingly good (10 4 ) for both two devices . The I ph of the two devices (with and without Ag/OPCs) were 321 and 41 nA, respectively.…”

Guided Growth of Horizontal ZnS Nanowires on Flat and Faceted Sapphire Surfaces

“…Various semiconducting materials such as GaN 13,[19][20][21] , ZnO [22][23][24] , ZnSe [25][26] , ZnTe 27 , CdSe 28 , CdS [29][30] and CsPbBr3 31 were grown into aligned NW arrays, guided by epitaxial and graphoepitaxial relationships with the substrate. The epitaxial growth is usually driven by the minimization of the mismatch between the NW and the substrate, which controls the growth along specific lattice directions and crystallographic orientation ( Figure.…”

Recent advances in low‐dimensional semiconductor nanomaterials and their applications in high‐performance photodetectors

“…The PDs fabricated by CdS@CdSe core‐shell nanowalls have a photocurrent response speed of about 200 ns on average, and have a high response rate of 1.2 × 10 3 A W −1 and a high gain photocurrent. The main reason is that the core‐shell heterostructure enhances the charge‐separation efficiency of the nanowall . The 1D/0D heterostructure also demonstrates the addition and enhancement of single materials.…”

“…The main reason is that the core-shell heterostructure enhances the charge-separation efficiency of the nanowall. 181 The 1D/0D heterostructure also demonstrates the addition and enhancement of single materials. For example, PDs based on ZnO NWs arrays and PbS QDs have a wider spectral range of light detection capability and faster response speed than ZnO PDs.…”