Electrically Tunable Multiple‐Effects Synergistic and Boosted Photoelectric Performance in Te/WSe2 Mixed‐Dimensional Heterojunction Phototransistors

Abstract Mix‐dimensional heterojunctions (MDHJs) photodetectors (PDs) built from bulk and 2D materials are the research focus to develop hetero‐integrated and multifunctional optoelectronic sensor systems. However, it is still an open issue for achieving multiple effects synergistic characteristics to boost sensitivity and enrich the prospect in artificial bionic systems. Herein, electrically tunable Te/WSe2 MDHJs phototransistors are constructed, and an ultralow dark current below 0.1 pA and a large on/off rectification ratio of 106 is achieved. Photoconductive, photovoltaic, and photo‐thermoelectric conversions are simultaneously demonstrated by tuning the gate and bias. By these synergistic effects, responsivity and detectivity respectively reach 13.9 A W−1 and 1.37 × 1012 Jones with 400 times increment. The Te/WSe2 MDHJs PDs can function as artificial bionic visual systems due to the comparable response time to those of the human visual system and the presence of transient positive and negative response signals. This work offers an available strategy for intelligent optoelectronic devices with hetero‐integration and multifunctions.


I. Growth and Characterization of Te thin films grown by MBE
The Te thin films were grown by MBE on mica (001) with an ultrahigh vacuum background pressure of 1×10 -10 Torr.Te (99.9999%) solid source was evaporated from Knudsen cell at 350 ℃ for 20 minutes and the substrate is heated at 220℃.In situ reflection high-energy electron diffraction (RHEED, STAIB Instruments NEK 300R3-8) with a voltage of 20 kV and current of 1.6 A was applied to monitor the whole growth processes.The RHEED result shows it highly oriented single crystal.The highresolution X-ray diffraction (HRXRD) spectrum as well reciprocal space mapping (RSM) show that Te (003) peak in addition to mica (00l) peaks, which indicating a substantially strong preference for the Te epi-film from the out-of-plane ( 001   The light intensity dependence on the photocurrent is present in Figure S3 for VGS = 0 V.The fitting exponent k values are 0.85, 0.97 and 0.61 with VDS of -5 V, 0 V and 5 V, respectively.Figure S5 shows the power dependence of the D* at VGS = 50 V, and the peak value is 1.37 × 10 12 Jones at a light power density of 0.02 mW cm -2 when VDS = -5 V.The detection characteristics under an 830 nm laser illumination and 50 V are present in Figure S6 (a-c) for VGS at 0 V and (d-f) for VGS at 50 V.Here the VGS of 50 V significantly enhances both R and D* when applying a positive VDS.Wavelength VDS VGS > 0 V 0 V Figure S1.Structural characterization of MBE growth Te thin films.a) RHEED patterns of Te thin films after growth.b) HRXRD 2θ-ω diffraction patterns of Te/Mica.c) Rocking curve of Te (003) diffraction peak.d) Phi-scan along Te (105) direction.e) The asymmetric RSM of Te/mica.f) SEM images of the surface of Te thin films.The scale bar is 1 μm.g) Optical image of Te thin films.h)and i) Hall measurement result of Rxx and Rxy, showing carrier density of 7 × 10 18 cm-3 and mobility of 21 cm -2 V -1 s -1 at 300 K.

Figure
Figure S2 shows the p-type conduction characteristic of Te whereas WSe2 is an

Figure S4 .
Figure S4.Output curves in the dark case and under a 638 nm laser illumination with various power densities at VGS = -50 V.

Figure S5 .
Figure S5.Power dependence of the Detectivity at VDS = -5 V, 0 V and 5 V when VGS at 50 V.

Figure S6 .
Figure S6.Optoelectronic properties of the Te/WSe2 vdWH PDs under a 830 nm laser.Output curves with various power densities (a), Power dependence of R (b), and D* (c) at VGS = 0 V. Output curves with various power densities (d), Power dependence of R (e), and D* (f) at VGS = 50 V.

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Figure S7.exhibits the transient PTE response behaviors of Te/WSe2 PDs from 638nm

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Figure S8.(a) Time-resolved photocurrent spectra of Te/WSe2 PDs at different frequencies.(b) Normalized photocurrent variation with frequency