Ultra‐High Speed, High‐Sensitivity Spin‐Cast MXene‐Semiconductor‐MXene Photodetectors

Abstract

A simple room‐temperature process of depositing MXene on a III‐V structure with embedded 2D electron gas (2DEG) is used, which results in a large area, 2×104µm2$2 \times {10^4}\mu {m^2}$, photodetector (PD) device that greatly outperforms vacuum deposited Ti/Au metal‐semiconductor‐metal (MSM) PD's. By co‐optimizing properties of 2D MXene contacts and the III‐V material heterojunctions, this device sets new operating records with responsivity up to 1.04 A W‐1 at low optical powers, corresponding to >230% internal quantum efficiency, dark current of 50 fAµm2$\frac{{fA}}{{\mu {m^2}}}$, >105.6‐dB dynamic range, and 25–150 ps response time, which improves the previous MXene‐Semiconductor‐MXene responsivity by >2.7 times and is 7 × 103 –−106 times faster compared to other MXene‐based PDs. This is achieved by enhancing the Schottky barrier height by forming a Van der Waals (vdW) heterojunction between a wide bandgap AlGaAs surface layer and spin coated Ti3C2Tz electrodes. A layered architecture transports the optically generated electrons to a 2DEG channel at the GaAs/AlGaAs heterointerface, where they are rapidly collected. The landscaped electric field pushes the slow holes to an underlying low temperature‐grown GaAs (LT‐GaAs) region where they recombine. The proposed Schottky‐2DEG Photoconductor‐Schottky model for device operation shows how this device circumvents the canonical limitations of gain‐bandwidth product, and carrier transit time, while replacing the need for vacuum deposition of gold or other precious metals.

2D MXene Electrode-Enabled High-Performance Broadband Photodetector Based on a CVD-Grown 2D Bi2Se3 Ultrathin Film on Silicon

“…The Raman spectra of Ti 3 C 2 T x (T x = –F, −OH and –O) is shown in Figure S3­(b). The observed Raman bands are mainly A 1g (outer-plane vibrational mode of Ti–C) and E g (in-plane vibrational modes of Ti, C, and surface groups), which matches quite well with previous reports Figure (a) illustrates the absorption spectra of the Ti 3 C 2 T x MXene, where it shows nearly flat and low absorption in the visible to NIR region, and there is a rise in absorption in the region 730–860 nm due to surface plasmon resonance …”

“…The observed Raman bands are mainly A 1g (outer-plane vibrational mode of Ti−C) and E g (in-plane vibrational modes of Ti, C, and surface groups), which matches quite well with previous reports. 36 Figure 4(a) illustrates the absorption spectra of the Ti 3 C 2 T x MXene, where it shows nearly flat and low absorption in the visible to NIR region, and there is a rise in absorption in the region 730−860 nm due to surface plasmon resonance. 50 The conductivity (σ) of the as-prepared Ti 3 C 2 T x film was measured using the standard four-probe method with the standard geometric correction factor for isotropic infinite 2D sheets.…”

“…Furthermore, the electronic structure of MXenes can be altered by different surface terminating groups, allowing tuning of their work function (ranging from 1.6 to 6.2 eV). , Most significantly, MXenes are composed of atomic layers that are covalently bonded within the plane, exhibiting weak interactions with each other in the out-of-plane direction. When they are deposited onto bulk semiconductor materials, the resulting van der Waals junction at the interface remains chemically ordered and free from defect states, which helps to prevent the Fermi-level pinning effect and reduces the occurrence of reverse tunneling currents. , Simple spin-coating methods under ambient conditions can be used for MXene deposition, which makes MXene electrodes highly attractive for replacing conventional metal electrodes in optoelectronic devices. − Noble metals are relatively expensive, and their deposition often requires complex and expensive ultrahigh vacuum processes. Further, due to the relatively high work function of MXene compared to conventional metal electrodes, this can be a good choice as an electrode to achieve higher band bending and efficient charge separation across the junction.…”

Green Alga-Inspired Underwater Vision Based on Light-Driven Active Ion Transport across Janus Dual-Field Heterostructures

“…When illumination was carried out, free electrons and holes could be generated. Then photoexcited electrons from the Cu-HHTP would jump to the metal-like MXene more quickly, whereas the generated holes stayed in Cu-HHTP, as the electrons tend to transfer from the semiconductor with smaller work function to the metal in the presence of the formed Schottky junction. , After the efficient separation of photoexcited charge carriers between MXene and Cu-HHTP, an intramembrane electric field would be built to provide a photo-driven force for active cation transport from Cu-HHTP to MXene (Figure b). Simultaneously, photothermal MXene can convert absorbed light to heat efficiently upon light illumination, taking advantage of its larger extinction coefficient and localized surface plasmon resonance effect (Figure c). , As a result, a temperature gradient across the J-HM is generated to drive the thermo-osmotic cation transport from nonilluminated to illuminated sides through the nanochannels.…”

Non-covalent Functionalized Schottky Interface at Ti3C2Tx/n-Si Van der Waals Heterojunction

“…transition metal-based carbides, nitrides and carbonitrides 2D layered ceramics also known as MXene´s has drawn significant attention from the materials research community [8] . Thanks to their impressive physicochemical and charge transport properties this fascinating class of materials has found application in many different fields from energy conversion [9,10] /storage [11] to efficient electromagnetic shielding, photodetectors [12][13][14][15][16][17] , sensors [18,19] and biomedical devices [20] . To this date tens of different MXene compositions has been successfully synthesized and studied whereas possibility of synthesis of more than hundred different compositions has been predicted by the computational studies.…”