Gate-tunable rectification and photoresponse in a MoTe₂/SnS₂ van der Waals heterostructure based P–N diode

Abstract

The p–n junction, one of the prominent electrical components capable of being utilized in electronics and optoelectronics, has attracted renewed interest due to recent research in two-dimensional (2D) materials. In this work, we constructed a heterostructure p–n diode based on MoTe₂ and SnS₂. Sweeping the back-gate voltage (V_bg) effectively results in a high rectification ratio of 2.79 × 10⁵ at V_bg = +10 V and the lowest ideality factor (η) of about 1.25 was achievedwhen V_bg = −30 V. The interlayer electron–hole recombination is responsible for the variation in rectification behavior. This photodiode exhibits effective photodetection capabilities and promising merit statistics. The maximum change in photocurrent (I_ph) is measured to be about 90 nA at V_ds = 0.9 V, and the device exhibited a high responsivity (R) of 5.8 × 10⁴ mA W⁻¹, while the maximum external quantum efficiency (EQE) and detectivity are calculated to be about 3.27 × 10⁴ (%) and 2.47 × 10¹⁰ Jones for the device, respectively, when illuminated with 220 nm wavelength incident light at a power intensity of 11 mW cm⁻². The average rise/fall times for the 220 nm wavelength at V_ds = 0.9 V are observed to be 0.29 s/0.38 s, respectively. We examined the photoresponse of the device as a function of time at different wavelengths (λ = 970–220 nm) of the incident light and at different power intensities (P = 11–44 mW cm⁻²) of the incident light. The maximum values of V_oc = 0.32 V and I_sc = −0.40 nA were achieved at P = 44 mW cm⁻². The p-MoTe₂/n-SnS₂-based device has excellent rectifying and optoelectronic properties.

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Introduction

Two-dimensional (2D) layered materials are considered to have outstanding potential in electronics and optoelectronics due to their desirable physical characteristics.^1,2 Because of their customized energy band alignments and ultrathin structural characteristics, van der Waals (vdW) heterojunctions established on thin 2D materials have ushered in a new era for next-generation optoelectronics.³ Graphene has received a great deal of attention in the fields of spintronics,^4–6 electronics,⁷ and optoelectronics.^7,8 In another class, depending on the layer thickness, 2D transition metal dichalcogenide (TMDC) materials have band gaps between 1 eV and 2.5 eV. A broad range of applications, including photodetectors,^9,10 field-effect transistors,^11,12 flexible devices,¹³ logic circuits,¹⁴ and optical communication,^15,16 are possible due to the band gap variation between the multilayer indirect gap and the monolayer direct gap.^17,18 Ever more research has focused on p–n junctions made of various 2D layered materials, creating a new material platform for investigating novel physical features and new device applications.^19–21 One may tune the energy band alignment by joining individual layers of different 2D layered materials for the vdW heterostructure with a sharp junction at the atomic scale. This provides a wealth of options for investigating the fundamentals of new electrical and optical features. Thus, TMDCs/TMDCs or TMDCs/graphene heterostructures have been the focus of current studies in the field of 2D TMDCs.^22,23 In addition, due to their ultrathin nature and steep interfacial charge-carrier gradient, 2D vdW heterostructures have significant tunability in band alignment and carrier density, providing an alternative avenue for versatile electrical and optoelectronic applications. For example, in atomically thin GaTe/MoS₂ and WSe₂/MoS₂ p–n heterojunctions, the external quantum efficiency (EQE) of 40–60% is attained.^23,24 In addition, photodetectors based on MoTe₂/MoS₂ vdW heterojunctions are also demonstrated,^25,26 and gate-tunable photovoltaic behavior is also seen in WSe₂/MoS₂ heterojunctions.²⁷ Gate tunable rectification and photoresponse of the heterostructure GeSe/WS₂ based p–n diode were also observed.²⁸ Yet, due to the limited photocurrent flow without an external bias control, the responsivity of such devices remains low. As a result, greater efforts are required to increase the effectiveness of photodetectors based on TMDCs for future nanoscale optoelectronic devices. Molybdenum ditelluride (MoTe₂) has played a significant role in electronic devices. MoTe₂ exhibits a direct band gap that ranges from 0.9 to 1.1 eV, depending on the material's thickness and lattice structure.²⁹ MoTe₂ has potential use in a variety of devices, including digital logic circuits,³⁰ solar cells,³¹ and chemical sensors³² owing to its effective mobility and lack of dangling bonds. SnS₂ offers intriguing opportunities for creating heterostructures with other 2D materials with various crystallographic structures. A band gap of 2.28 eV is thus found that corresponds to the band gap of SnS₂.³³ SnS₂ has been identified as an n-type semiconductor because of its technological significance for next-generation electronic/photonic applications. Thus, layered two-dimensional (2D) SnS₂ has garnered significant interest.^34,35

Here, we present a heterostructure p–n diode consisting of MoTe₂ and SnS₂. Sweeping the back-gate voltage effectively results in a high rectification ratio of 2.79 × 10⁵. The variance in rectification behavior is caused by interlayer electron–hole recombination. Effective photodetection and inspiring merit statistics characterize this photodiode. The maximum change in photocurrent (I_ph) is measured to be about 90 nA. The device exhibited a high responsivity (R) of 5.8 × 10⁴ mA W⁻¹, while the maximum external quantum efficiency (EQE) and detectivity (D*) are calculated to be about 3.27 × 10⁴ (%) and 2.47 × 10¹⁰ Jones for the device when illuminated with incident light at a wavelength (λ) of 220 nm and a V_ds of 0.9 V, respectively. Furthermore, the photoresponse of the device was investigated under the illumination of light of various wavelengths and at different power intensities of incident light. The p-MoTe₂/n-SnS₂-based device exhibits remarkable optoelectronic and rectifying characteristics.

Device fabrication and characterization

Thin layers of MoTe₂ and SnS₂ were formed using the mechanical exfoliation method. Using an adhesive tape, flakes of both materials were mechanically exfoliated. These were then captured by a polydimethylsiloxane (PDMS) stamp on a glass slide as part of the transfer procedure. By positioning the PDMS stamp on a Si/SiO₂ substrate and peeling it off, few layers of SnS₂ and then MoTe₂ are transferred to the target substrate using the dry transfer method. A micro-aligner stage was used to carefully manage the transfer of each flake, which was monitored by a CCD camera. Then the substrate containing these layers (heterojunction) was dipped into acetone/methanol for 2 hours for the removal of residues. After this, the substrate was dried using nitrogen (N₂) gas. Polymethylmethacrylate (PMMA) was coated on the substrate that contains the heterostructure of MoTe₂–SnS₂, and contact electrode patterns were formed by e-beam lithography on the layer. Then the contact electrodes composed of Cr/Au (5 nm/60 nm) were deposited using a thermal evaporator. Then, the substrate was placed in acetone/methanol for the removal of unwanted metals, after this the substrate was dried using nitrogen gas. Finally, we connected the gate at the back (V_bg: back gate) of the Si/SiO₂ substrate with indium wire. The schematic of the device that contains the heterostructure of MoTe₂–SnS₂ is illustrated in Fig. 1(a). The scanning electron microscopy (SEM) image of the MoTe₂–SnS₂-based device is presented in Fig. 1(b). An atomic force microscope (AFM: Nano Focus) is employed to verify the thickness of the heterostructure. Fig. 1(c) depicts the AFM image of the device and thickness of the heterostructure of MoTe₂–SnS₂. The Renishaw spectrometer with a 514 nm excitation wavelength is utilized to check the Raman spectra. The Raman peak shows the basic characteristics of the MoTe₂–SnS₂ heterojunction as shown in Fig. 1(d). Two peaks can be seen in the Raman spectra of MoTe₂ at 172.4 cm⁻¹ and 232.9 cm⁻¹, respectively. These peaks correspond to the out-of-plane vibrational mode A_1g and the in-plane vibrational mode E¹_2g, and the A_1g mode at 315.7 cm⁻¹ corresponds to SnS₂. The individual Raman spectra of both MoTe₂ and SnS₂ are presented in Fig. S1(a and b) (ESI†). For SnS₂, in the heterojunction region, the peak got contribution of both materials, representing the presence of two different materials. Specifically, a reduction in the peak intensity for SnS₂ due to screening from MoTe₂ is clearly observed. In addition, we have observed a minor blue shift for the peak corresponding to A_1g, this may be due to the transfer of holes from MoTe₂ to SnS₂ material, and a minor blue shift is also seen in the peaks of MoTe₂ after stacking with SnS₂.

Fig. 1 (a) Schematic illustration of the p–n device. (b) SEM image of the p–n heterostructure MoTe₂–SnS₂-based device; the scale bar is 5 μm. (c) AFM profile of the heterostructure. (d) Raman spectra of the MoTe₂–SnS₂ heterostructure.

We created intensity maps to visualize their spatial distribution across the heterostructure. These maps represent the variation in Raman intensity at specific Raman shift values and provide insights into the distribution and interaction of the materials within the heterostructure. We have observed the Raman intensity of MoTe₂/SnS₂, which shows that the MoTe₂ and SnS₂ grains are laterally and flawlessly spliced in the heterostructure without the construction of alloy phases at their junction. The area selected for Raman mapping investigated is highlighted in Fig. 2(a). Graphical depiction of the Raman intensity mapping obtained at 172.43 (A_1g), and 232.93 cm⁻¹ (E¹_2g) for MoTe₂, and 315.78 cm⁻¹ (A_1g) for SnS₂ is shown in Fig. 2(b–d). The Raman mapping data show the perfect formation of the vdW heterostructure based on MoTe₂–SnS₂.

Fig. 2 (a) Optical image of the device that shows the area selected for Raman mapping. (b) Raman intensity maps of A_1g of MoTe₂. (c) Raman intensity maps of E¹_2g of MoTe₂. (d) Raman intensity maps of A_1g of SnS₂. Graphical representation of Raman intensity mapping at 172.43 and 232.93 cm⁻¹ for MoTe₂, and 315.78 cm⁻¹ for SnS₂.

The materials MoTe₂ and SnS₂ were characterized by X-ray photoelectron spectroscopy (XPS). We have utilized an XPS (PHI 5000 Versa Probe III, ULVAC PHL, Japan), with a monochromatic Al Kα (1486.6 eV) X-ray source with a beam spot size of ∼20 μm. Fig. 3(a and b) shows the XPS spectra of Mo and Te, and the fitted peaks for the MoTe₂ flake are consistent with the previously reported results.³⁶ The corresponding valence band maximum (VBM) spectra of MoTe₂ are presented in Fig. 3(c) and are valued at ∼0.10 eV. Fig. 3(d and e) shows the XPS spectra of Sn3d_5/2, Sn3d_3/2, S2p_3/2 and S2p_1/2. The VBM spectra of SnS₂ are depicted in Fig. 3(f), which correspond to the value of ∼1.53 eV. The fitted Sn and S₂ binding energies of SnS₂ are in good agreement with the previous report.³⁷ The XPS peaks are well defined and show that the flakes of MoTe₂ and SnS₂ are of high quality with no detectable oxidation state present on the surface of flakes. The separation between Mo3d_3/2 and VBM_MoTe2 and Sn3d_5/2 and VBM_SnS2 is illustrated in Fig. S2(a) (ESI†). Based on the XPS data, we have approximately calculated the band alignment of MoTe₂–SnS₂-based sample. The valence band offset is observed to be ≈1.43 eV, and the detailed calculation is shown in the ESI.† Based on valence band offset (VBO) approximate data obtained through XPS, we have calculated the conduction band offset (CBO) of 0.25 eV for MoT₂–SnS₂ and illustrated the band alignment. The detailed calculation is shown in Fig. S2(a and b) (ESI†).

Fig. 3 XPS spectra: (a) Mo 3d peaks. (b) Te 3d peaks. (c) VBM of MoTe₂. (d) Sn 3d peaks. (e) S 2p peaks. (f) VBM of SnS₂.

Results and discussion

Electrical and photoresponse investigation

The IV curves were obtained at various back gate voltages (V_bg) using a Keithley 2400 (source meter) and a picometer (Keithley 6485) to assess the drain current. The photoresponsivity and EQE were evaluated using a light source of various wavelengths and irradiation power of different intensities. All measurements were taken at room temperature, to allow light illumination of the whole sample, and the device was placed inside a closed glass box under a high vacuum.

Electrical transport and rectification effects in MoTe₂/SnS₂ p–n diodes

The electrical characteristics of both materials were examined individually also, and the I–V curves of separate MoTe₂ and SnS₂ at various back gate voltages are exhibited in Fig. S3(a and b) (ESI†). Each MoTe₂ and SnS₂ transfer curve exhibits obvious p- and n-type characteristics, respectively, as presented in Fig. S3(c and d) (ESI†). The source electrode was linked to MoTe₂ (p-type) in our measurement approach, whereas drain contact was linked with SnS₂ as indicated in Fig. 1(b). The I–V characteristics curves in linear scale for the MoTe₂–SnS₂ heterostructure at various back gate voltages are illustrated in Fig. 4(a), where the source–drain voltage range is −2 V to +2 V. The IV relation employed for typical p–n diodes made of semiconductors may be utilized to investigate the output properties of vdW's heterojunction-based p–n devices.³⁸ The following equation provides the value for the current “I” via the diode:where I_s refers to the saturation current, k is the Boltzmann constant, η refers to the ideality factor and q is the electronic charge. The I–V curves of the p–n diodes are presented in logarithmic scale as shown in Fig. 4(b). We define the rectification ratio (R.R = I_f/I_r) as the fraction of the forward current (I_f) and reverse-bias current (I_r) in order to test the rectification effect. We have attained a high rectification ratio of 2.79 × 10⁵ at back gate voltage V_bg= +10 V during the back-gate sweep effectively. Since I_r reduces more successfully in the negative V_bg than in the previously reported BP/MoS₂ configuration, the R.R value is increased further three times.^39,40 The high rectification rate is ascribed to two causes. The larger barrier height for V_bg < 0 V is the first explanation for the reduced reverse-bias leakage current. Expectedly, the barrier height between MoTe₂ and SnS₂ decreases for the positive V_bg, which in turn brings down the depletion width. Similar to this, a negative V_bg raises the barrier height and widens the depletion breadth. The tuning of the Schottky barrier (SB) height through gate-voltage at the metal/TMDC contact is the additional factor that causes the enhancement of the rectification ratio. The variation in the rectification ratio of the device at various gate voltages is illustrated in Fig. 4(c). V_bg has a significant impact on the MoTe₂/SnS₂ heterojunction p–n diode's output characteristics. The ideality factor at different back gate voltages is calculated; the variation in the ideality factor at various gate voltages is represented in Fig. 4(d). The detailed calculation for the ideality factor is expressed in the ESI† (Fig. S4). The lowest value of ideality is 1.25, which is achieved at V_bg = −30 V.

Fig. 4 (a) I_ds–V_ds characteristic curves of the MoTe₂–SnS₂ heterostructure at various back gate voltages (V_bg); the linear scale. (b) Logarithmic scale. The maximum rectification ratio is 2.79 × 10⁵ mA W⁻¹. (c) The change in the rectification ratio of the device at various back gate voltages. (d) The variation in the ideality factor at different gate voltages.

Fig. 5(a) demonstrates the energy-band diagram in p-MoTe₂ and n-SnS₂ with work functions, conduction band (CB) minima, and valence band (VB) maxima. In the case of SnS₂, the Fermi level is close to the CB, which displays n-type behavior, while the Fermi level of MoTe₂ is close to the VB, which displays p-type behavior. The band diagram of the MoTe₂/SnS₂ vdW heterostructure at zero V_bg is shown in Fig. 5(b) along with the associated Fermi level. The second part depicts a zoomed-in picture of the band configuration following the contact with zero V_bg. The Fermi level may be manipulated using the gate voltage, which modulates the charge carrier densities (holes and electrons) in p-MoTe₂ and n-SnS₂, correspondingly, and hence the rectification ratio as well. The Fermi level shifts away from the “CB” at V_bg < 0 V, increasing the potential barrier at the junction of the MoTe₂/SnS₂ vdW heterostructure diode, which generates a strong rectifying current. When V_bg > 0 V, the Fermi level moves toward the CB, lowering the barrier height. The manipulation of charge carriers (holes and electrons) and band positions of the MoTe₂/SnS₂-based diode by gate voltage offers an alternative way to fabricate very competent vdW heterojunctions.

Fig. 5 Schematic illustration of the band diagram for the p-MoTe₂/n-SnS₂ structure-based diode at V_bg = 0 V. (a) Schematic signifies the band diagram of a p-MoTe₂/n-SnS₂ diode before connection, and (b) symbolizes the diode after connection.

Optoelectronic properties of MoTe₂/SnS₂ p–n diodes

The optoelectronic properties of devices made of 2D materials have been the focus of ongoing research. Because the charge transfer differs from that of common p–n diodes, we studied the photoresponse to further investigate the potential exciting optoelectrical performance. The p-MoTe₂/n-SnS₂ heterojunction has high photovoltaic capabilities in addition to good electric qualities. The schematic of the photocurrent measurement approach is illustrated in Fig. 6(a), where the device is placed in a glass vacuum chamber. DUV light was beamed on the diode, causing a significant number of electron–hole pairs to form in both the SnS₂ and MoTe₂ layers. These photoinduced charge carriers penetrate the barrier, producing a strong photoresponse. The individual photocurrents of the 2D layers MoTe₂ and SnS₂ at different gate voltages are presented in Fig. S5 and S6 (ESI†), respectively. The MoTe₂/SnS₂ p–n diode is lit by light with the wavelength (λ) of 220 nm and an irradiation power (P) of 11 mW cm⁻². The photocurrent of the device at various source–drain voltages (V_ds) based on the MoTe₂–SnS₂ heterostructure is shown in Fig. 6(b). This illustrates how the photocurrent changes as a light is turned on and off repeatedly. A probable photo-switching mechanism is suggested by the photocurrent's on-and-off switching behavior. The maximum change in photocurrent (I_ph) is found to be about 90 nA at V_ds = 0.9V. Due to a rise in the built-in potential and charge carrier, we saw that the value of photocurrent rose at higher voltages. The large photovoltaic behavior is caused mostly by type-II band arrangement and a greater built-in potential at the junction, which efficiently distinguishes the photo-excited electron–hole pairs. The device exhibited a high responsivity (R) of 5.8 × 10⁴ mA W⁻¹ at V_ds = 0.9 V. The following formula is used to derive the photoresponsivity (R).where P is the incident light power, A is the effective area (14 μm²) and I_ph is the photocurrent. The detectivity D* = RA^1/2/(2e.I_dark)^1/2 is also calculated, where R denotes responsivity, “A” is the effective area, e is the charge of the electron, and I_dark is the dark current,^41,42 and the detectivity (D*) is about 2.47 × 10¹⁰ Jones. The electrons and holes collected in the n-SnS₂ and p-MoTe₂ layers, respectively, result in the development of an open-circuit voltage (V_OC). These retrieved electrons and holes in SnS₂ and MoTe₂ quickly recombine through an external circuit, producing a short-circuit current (I_SC). At room temperature, our device represented an open circuit voltage (V_oc) of 0.20 V and a short circuit current (I_sc) of −8.5 nA and when V_g = 0 as presented in Fig. 6(c). This is due to the high photo-absorption and effective photoinduced electron–hole pair production. The amount of photo-generated carriers per incident photon per second is defined as the EQE, and the following equation was used to obtain the EQE,^43,44where ‘h’ refers to Plank's constant, c denotes the speed of light, e is the electron charge (e), and λ is the wavelength of light. The EQE value is determined from light absorption and the buildup of photo-generated carriers. In comparison to all previously reported p–n heterojunctions, we achieved the greatest EQE (%) of 3.27 × 10^4% at V_ds = 0.9 V, along with improved responsivity and other electronic/optoelectronic characteristics.^45–47 The change in “R” and “EQE” at different V_ds is depicted in Fig. 6(d). Moreover, because of the significant built-in potential, a quick photo-carrier separation and the associated short transit time may lead to a significant gain and a significant EQE.^48,49Fig. 6(b and c) indicate that the rise in the forward- and reverse-bias currents is related to the creation of electron–hole pairs brought on by illumination. When illuminated, the charges are separated at the junction,^50,51 causing the electrons to collect on the top face of the SnS₂ and the holes to belong to the bottom face of MoTe₂. Due to the formation of dipoles in the junction region, increased electron–hole pair production is subsequently induced.⁵² Our MoTe₂/SnS₂ heterojunctions were shown to have a significant promise for both electrical and optoelectronic devices due to their effective photoresponsivity and high EQE. Another cause for the high EQE is the built-in voltage at the interface.^24,53 Due to the slight difference among “CB” maximums of MoTe₂ and SnS₂, electrons and holes recombine in greater quantities at the junction between MoTe₂ and SnS₂, increasing the built-in potential. Furthermore, it is envisaged that the screening against coulomb impurities would be improved in the devices based on 2D materials, resulting in a larger EQE.²⁴ The average rise/fall time is 0.29 s/0.38 seen for the wavelength of 220 nm at V_ds = 0.9 V, respectively. The fitting/calculation details related to rise/fall time is shown in tabular and graphical form in Fig. S7(a and b) (ESI†).

Fig. 6 (a) Schematic of the p–n device for photodetection. (b) Photocurrent at V_g = 0, for V_ds= 0.2–0.9 V with incident light (λ = 220 nm) and power intensity 11 mA cm⁻². (c) I–V curves in the dark and under light, representing I_SC = −8.5 nA and V_oc = 0.20 V at V_g = 0. (d) The change in responsivity at different values of V_ds. (e) The enhancement in the EQE at different values of V_ds.

We have examined the photoresponse of the device as a function of time at different wavelengths (λ = 970, 650, 365 and 220 nm) of the incident light at V_ds = 0.5 V as shown in Fig. 7(a). The photocurrent of the device is enhanced as the wavelength of incident light is decreased. The observed photocurrent rises as the wavelength decreases, reaching its maximum value at λ = 220 nm because of the higher production of electron–hole pairs at low wavelengths. Because there are more excited charge carriers, smaller wavelengths produce greater photocurrent and responsivity values. This behavior is related to strong absorption and high photon energies at low wavelengths, which is compatible with the findings of earlier research.⁵⁴ We have calculated the responsivity (R) and external quantum efficiency (EQE) at various wavelengths of incident light. The values of R and EQE decreased as the wavelength of incident light was enhanced as shown in Fig. 7(b). Photoresponse of the device based on the MoTe₂/SnS₂ heterostructure was investigated as a function of time at different power intensities (P = 11, 20, 35, 44 mW cm⁻²) of the incident light at a wavelength λ = 220 nm for V_ds = 0.5 V shown in Fig. 7(c). We have seen that the photocurrent is enhanced as the power of radiant light is raised. Fig. 7(d) shows the IV curves under dark and incident light of different power intensity, and we can observe the change in V_oc and I_sc. It is observed that as the incident light's intensity increases, the reverse current rises steadily under the light. This is due to greater electron–hole pairs being generated at the p-MoTe₂/n-SnS₂ junction because of the incoming light, increasing the reverse and forward currents. Furthermore, V_oc is non-linear and the value of I_sc is linearly reliant on the intensity of the laser light as shown in Fig. 7(e). The maximum values of V_oc = 0.32 V and I_sc = −0.40 nA were achieved at P = 44 mW cm⁻². Furthermore, we added the Table 1 that summarizes the various characteristics of different photodetectors based on various 2D materials. The p-MoTe₂/n-SnS₂-based device exhibits remarkable optoelectronic and rectifying characteristics.

Fig. 7 (a) Photocurrent of the device based on the MoTe₂/SnS₂ heterostructure as a function of time at different wavelengths of incident light. (b) Change in R and EQE as a function of wavelength, which shows a decreasing trend. (c) Photoresponse of the device at different power intensities of incident light at the wavelength of 220 nm. (d) I–V characteristics curve of the device under the dark and with the radiant light of different power intensities. (e) Variation in V_OC and I_SC under different power intensities of radiant light (P = 11, 20, 35, 44 mW cm⁻²).

Table 1 The summary of photodetectors based on various 2D materials

Materials	Wavelength (λ)	Responsivity	Detectivity (D*) Jones	EQE (%)	Ref.
GaSe/PtSe2	520 nm	1.78 A W^−1	3.5 × 10^12	405	55
WSe2/ReS2	600 nm	3 A W^−1	8.39 × 10^10	600	56
BP/MoS2	Near IR (532 nm)	22.3 A W^−1	3.1 × 10^11	∼10^3	57
PtSe2/GaAs	200–1200 nm	0.262 A W^−1	2.52 × 10^12	—	58
GeAs/ReS2	532 nm	6.86 × 10^3 mA W^−1	1.2 × 10^9	1639%	59
	1550 nm	1.02 × 10^2 mA W ^−1	2.16 × 10^8
GaSe/MoS2	520 nm	0.67 A W^−1	2.3 × 10^11	∼160%	60
SnS2/MXene Nb2C	365 nm	102.44 μA W^−1	7.48 × 10^12	—	61
GaSe/SnS2	633 nm	∼35 A W^−1	8.2 × 10^13	62	62
MoTe2/SnS2	220 nm	5.8 × 10^4 mA W^−1	2.47 × 10^10	3.27 × 10^4 (%)	This work

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Conclusion

Finally, on Si/SiO₂, we created a stable MoTe₂/SnS₂ vdW's heterostructure p–n diode. The device has a rectifying effect that is highly dependent on the back-gate voltage. One can create a vdW heterojunction p–n diode that performs the rectifying function in transparent and flexible electronics by using MoTe₂ and SnS₂ materials, respectively. Raman intensity mapping and XPS analysis are also employed to check the formation of the vdW heterostructure and quality of both materials MoTe₂ and SnS₂. A high rectification ratio of 2.79 × 10⁵ and the lowest ideality factor (η) of about 1.25 were achieved. Prospective nano-electronic and optoelectronic technologies that rely on MoTe₂ and SnS₂ heterostructures would include a variety of FETs, photodetectors, and advanced photovoltaic cells. The maximum change in photocurrent (I_ph) is found to be about 90 nA. The device exhibited a high responsivity (R) of 5.8 × 10⁴ mA W⁻¹, and the maximum EQE and detectivity are calculated to be about 3.27 × 10^4% and 2.47 × 10¹⁰ Jones for the device, at V_ds = 0.9 V for wavelength = 220 nm, respectively. Furthermore, the photoresponse of the device was also checked at different wavelengths of incident light, and with different power intensities of light. The p-MoTe₂/n-SnS₂-based device has excellent rectifying and optoelectronic properties. These heterojunctions should expand the possibilities for future nanoscale optoelectronic devices.

Author contributions

H. N. and E. E. conceived and designed the experiments, MAK helped in device fabrication. J. J performed the AFM analysis. E. E. performed the electrical and photo (DUV) measurements of the devices. SKJ helps in XPS analysis and proofread the article. A. A Al-K performed the Raman mapping and obtained photoresponse data at different wavelengths. H. N. and E. E wrote the final manuscript. All the authors have approved the final version of the manuscript.

Data availability statement

All data needed to evaluate the conclusions are present in this article and the ESI.† Additional data related to this article may be requested from the corresponding authors.

Conflicts of interest

The authors declare that they have no competing interests.

Acknowledgements

This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2020R1F1A1071556). The authors also thank the researchers supporting the project (RSP2023R266), and King Saud University, Riyadh, Saudi Arabia for their financial support.

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3tc01990j

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