Epitaxial Growth of 2D Ternary Copper–Indium–Selenide Nanoflakes for High‐Performance Near‐Infrared Photodetectors

Abstract

and chemical properties, including dangling-bond-free surface, atomic thickness, flexibility, high mobility, and tunable band gap. [1][2][3][4] These merits lead 2D materials to be expected to replace traditional photodetectors with the drawbacks of fragile quality, limited pixel size, and low-temperature operation in infrared region. [5][6][7] 2D layered materials have demonstrated attractive photoelectric properties, such as broadband detection, high photoresponsivity, high external quantum efficiency (EQE), high specific detectivity, and fast photoresponse, and thus could be promising candidates for future photodetectors in flexible electronics, biological imaging, and environmental monitoring. [8][9][10][11] However, the efficiency of photon trapping in 2D materials is relatively low. [12] Lots of efforts have been taken to improve the efficiency of photon trapping, such as constructing heterostructures with n-dimensional (n = 0, 1, 2) materials. [1] On the other hand, searching for new members of more photon-sensitive 2D materials is another effective way to improve the photodetector characteristics. [13][14][15] Initially, research was focused on single or binary elemental 2D materials, such as black phosphorus and transition metal dichalcogenides. Subsequently, ternary 2D materials have attracted increasing attention because of the flexibility to tune their composition and the emerging intriguing physical properties. [15][16][17] Devices based on ternary layered materials have exhibited outstanding photoelectric characteristics, which indicates that ternary 2D materials have promising applications in future photoelectric devices. [14,15] The copper-indium-selenium (CIS) system is composed of a series of typical ternary materials. The structure and physical properties of CIS can be tuned by changing the ratio of Cu/ In, and CIS materials are widely used as a light absorption layer in solar-energy applications. [18][19][20][21] Normally, CIS structures are n-type semiconductors with a direct band gap, except for CuInSe 2 which is a p-type semiconductor, and their Hall mobilities can reach 2.3 × 10 3 cm 2 V −1 s −1 . [22][23][24][25] CIS compounds usually have a chalcopyrite structure with different ordered vacancies. When the Cu/In ratio is between 1:5 and 1:9, the CIS system can contain layered structures. [17] Layered CIS nanoflakes such as CuIn 7 Se 11 can be exfoliated from the bulk single crystals, and they have been constructed into 2D semiconductors are promising for future photodetectors because of their dangling-bond-free surface, atomic thickness, tunable bandgap, high mobility, and flexible nature. However, the low light absorption is one of the main limits for the practical applications of 2D materials. Lots of efforts have been taken to optimize the light absorption, for example, constructing heterojunctions and exploring more photo-sensitive 2D materials. Here, the epitaxial growth of layered copper-indium-selenide (CIS) nanoflakes is realized by chemical vapor deposition. The CIS nanoflakes ar...

Ultra‐High Responsivity Black‐Si/Graphene Heterojunction Photodetectors Enabled by Enhanced Light Absorption and Local Electric Fields

“…Additionally, the specific detectivity (D*) is used to evaluate the ability of the device to detect weak signals in noisy environments. If we assume that the main noise is shot noise, the specific detectivity can be expressed as: [38]…”

“…Additionally, the specific detectivity ( D* ) is used to evaluate the ability of the device to detect weak signals in noisy environments. If we assume that the main noise is shot noise, the specific detectivity can be expressed as: [ 38 ] $$$$\begin{equation}{D}^* = R\sqrt {\frac{S}{{2e{I}_{{\mathrm{dark}}}}}} \end{equation}$$$$where e is the elemental charge value, I dark is the dark current. Because D * is proportional to R , it follows the same trend as R , as shown in Figure S4 (Supporting Information).…”

Axial InN/InGaN Nanorod Array Heterojunction Photodetector with Ultrafast Speed

“…[ 4–6 ] In this regard, the bandgap tunable semiconductor and its fabricated photodetector with fast response speed have become a research hotspot. [ 7–9 ]…”

“…[4][5][6] In this regard, the bandgap tunable semiconductor and its fabricated photodetector with fast response speed have become a research hotspot. [7][8][9] InGaN semiconductors can achieve wavelength-selective absorption owning to their tunable bandgap (0.65-3.4 eV), which is adjusted by varying the composition of Indium (In). [10][11][12] Thanks to the development of semiconductor industry technology, the InGaN photodetector with PIN and integrated structure has been used in visible light communication systems.…”