N-type Schottky Contact Research Articles

Interlayer coupling and external electric field controllable electronic structures and Schottky contact of HfSeX (X = S, Se)/graphene van der Waals heterostructures

Graphene-based van der Waals heterostructures (vdWHs) owing to their remarkable physical properties and extensive application attract much attention. However, the Schottky barrier height (SBH) at the interface limits the charge injection effect. Here, we investigate the geometry, electronic structures, contact behavior and optical properties of the HfSeX/graphene (HfSeX/G, X = S, Se) vdWHs via first-principles calculations. The effect of interlayer coupling and external electric field (Efield) on the HfSeX/G are examined. Our results show that the Dirac cones of graphene are well preserved in all modes due to weak van der Waals interaction and a small bandgap is opened in graphene. The SBH of n-type Schottky contact types (SCT) HfSe2/G, SHfSe/G and SeHfS/G vdWHs are 0.100, 0.085 and 0.114 eV, respectively. Both the interlayer distance and Efield can induce the n-type SCT of the Janus HfSSe/G to transfer to p-type, and large Efield can cause an Ohmic contact. The HfSeX/G heterostructures enhance light absorption intensity in visible-light region compared with isolate graphene and HfSeX monolayers. The work provides a valuable theoretical guidance for designing Schottky-based devices of the HfSeX/G heterostructures, as well as indicates that the heterostructures have a flexible application prospect in further optoelectronic and field effect transistors devices.

Interface contact and modulated electronic properties by external vertical strains and electric fields in graphene/MoS2 heterostructure

Based to the first-principles calculations, we study the electronic properties of graphene/MoS2 heterostructure by modulating the vertical strains and applying external electric field. Graphene/MoS2 heterostructure is a van der Waals heterostructure (vdWH) with the interlayer spacing is 3.2 Å for the equilibrium state, and the contact property of the interface is n-type Schottky contact. The Schottky barrier height (SBH) changes with vertical strains which induces a change of charge transfer between graphene and MoS2 layer. In addition, with strain or without strain, the applied positive electric field can effectively promote the charge transfer from graphene to MoS2, while the negative electric field has the opposite effect. These findings support for the design of field effect transistors based on graphene vdWHs.

Interfacial contact and electronic properties in the heterojunction based on black phosphorus and borophene

We study the electronic properties of heterostructures based on monolayer black phosphorus (BP) and two types of borophene (HBoro and BoroΔ). The contact between BP and borophene results in the disappearance of Schottky barriers, indicates the metallization of BP. The BP/HBoro forms an n-type Schottky contact and BP/BoroΔ forms a p-type Schottky contact between the channels and electrodes. The edge modification of BP also affects the Schottky contact type and Schottky barrier heights. Moreover, it is found that the gate voltage can not only effectively modulate the Schottky barrier height but also change the Schottky contact type of BP/borophene structures. The ohmic contact can be achieved at some certain gate voltage. The results provide a promising route to design and fabricate tunable devices based on edge modified BP with borophene electrodes.

Electric metal contacts to monolayer blue phosphorus: electronic and chemical properties

The contact nature when monolayer blue phosphorus (blueP) interfaces with three transition metal electrodes (i.e., Pd, Ir, and Pt) was unraveled by the ab initio density functional theory calculations. Specifically, n-type Schottky contact is observed for Ir(111)-blueP, in contrast, p-type Schottky contacts are formed for Pd(111)- and Pt(111)-blueP. The Fermi level is pinned partially at metal-blueP interfaces due to two interfacial behaviors: one being the modification of metal work function caused by interface dipole formation ascribed to a redistribution of charges, and the other being the production of gap states that are dominated by P p-orbitals since the intralayer PP bonds are weakened by the interfacial metal-P interactions. The incorporation of metal substrates would also significantly alter the chemical properties of the adsorbed monolayer blueP. The binding strength of hydrogen can be enhanced by as much as 0.9 eV, which resulted from two parts: one is the charge transfer from metal substrate to monolayer blueP rendering a stronger HP coupling; the other is a strong interfacial interaction after the hydrogen adsorption. The free energy change of H adsorption onto Ir(111)-blueP is as low as 0.16 eV which is comparable to the most efficient catalyst of Pt. These findings would provide theoretical guidance for the future design of electronic devices based on blueP and exploration of its potential in novel catalysts for hydrogen evolution reaction.

Engineering Schottky barrier in vertical graphene/InN heterostructure

In recent years, van der Waals stacked heterostructures (vdWHs) have gained much study interest for enhancing nanoelectronics’ performance. We take the first-principles methods to study the interface contact characters of the graphene/InN vdWH under the interlayer coupling and electric field. The natural electronic characters of both the graphene and InN components keep intact at the equilibrium interlayer distance with an n-type Schottky contact. Impressively, it tunes to Ohmic contact when the interlayer distance increases to 4.73 Å or the applying negative electric field increases to −0.42 V/Å, while it converts to p-type Schottky contact under a positive electric field greater than 0.2 V/Å. These findings are of great significance for the application of graphene/InN vdWH in high-performance nanoelectronics.

Modulation of Schottky barrier in XSi2N4/graphene (X = Mo and W) heterojunctions by biaxial strain

Reducing the Schottky barrier height (SBH) and even achieving the transition from Schottky contacts to Ohmic contacts are key challenges of achieving high energy efficiency and high-performance power devices. In this paper, the modulation effects of biaxial strain on the electronic properties and Schottky barrier of MoSi2N4 (MSN)/graphene and WSi2N4 (WSN)/graphene heterojunctions are examined by using first principles calculations. After the construction of heterojunctions, the electronic structures of MSN, WSN, and graphene are well preserved. Herein, we show that by applying suitable external strain to a heterojunction stacked by MSN or WSN — an emerging two-dimensional (2D) semiconductor family with excellent mechanical properties — and graphene, the heterojunction can be transformed from Schottky p-type contacts into n-type contacts, even highly efficient Ohmic contacts, making it of critical importance to unleash the tremendous potentials of graphene-based van der Waals (vdW) heterojunctions. Not only are these findings invaluable for designing high-performance graphene-based electronic devices, but also they provide an effective route to realizing dynamic switching either between n-type and p-type Schottky contacts, or between Schottky contacts and Ohmic contacts.

Mapping of contactless photoelectrochemical etched GaN Schottky contacts using scanning internal photoemission microscopy—difference in electrolytes

We present the experimental results on the mapping characterization of n-type GaN Schottky contacts with selective contactless photoelectrochemical (CL-PEC) etching by using scanning internal photoemission microscopy (SIPM). The CL-PEC etching was performed in four kinds of aqueous solutions (KOH mixed with K2S2O8 (oxidant), phosphoric acid mixed with oxidant, only oxidant, and ammonia). The Schottky barrier height (qϕ B) values decreased by less than 0.1 eV in the etching with the KOH and oxidant solutions. On the other hand, the opposite trend was observed for the samples etched with the phosphoric acid solution. Whereas the samples etched with the ammonia solution had a scattered qϕ B value, they were not affected by the etching. However, the photoyield increased by 2.5–3.5 times in all kinds of etching. SIPM was found to be sensitive in visualizing the effect of the CL-PEC etching as an image.

Electronic properties and controllable Schottky barrier of Janus HfSSe and graphene van der waals heterostructure

Based on the first-principles calculations, we studied the structure and electronic properties of HfSSe/Graphene (HfSSe/Gr) and Graphene/HfSSe (Gr/HfSSe) van der Waals heterostructures (vdWHs) under the effects of external electric field and interlayer distance. The results show that the electronic properties of HfSSe/Gr and Gr/HfSSe heterostructures are not sensitive to interlayer distance, and the heterostructures always maintain n-type Schottky contact when the interlayer distance changes. Under the different applied electric field, the Schottky barrier of heterostructures can be regulated from n-type Schottky contact to p-type Schottky contact, and it can be further adjusted to Ohmic contact. In summary, these results are useful in nanoelectronic and optoelectronic devices in the future experiments.

Modulation of MoSH/WSi<sub>2</sub>N<sub>4</sub> Schottky-junction barrier by external electric field and biaxial strain

In view of the newly synthesized two-dimensional (2D) semiconductor material WSi<sub>2</sub>N<sub>4</sub> (WSN) and the 2D metal material MoSH (MSH), a metal-semiconductor MSH/WSN Schottky-junction is constructed in this work. In practical applications of metal-semiconductor contact, the presence of the Schottky barrier degrades the device performance severely. Therefore, it is crucial to obtain a smaller Schottky barrier height or even an Ohmic contact. Here, the first-principles calculations are used to investigate the variation of the Schottky barrier in MSH/WSN Schottky-junction under an external electric field and a biaxial strain. The results show that both external electric field and biaxial strain can effectively modulate the Schottky barrier of the MSH/WSN Schottky-junction. The dynamic switching between the p-type Schottky contact and the n-type Schottky contact can be achieved under the action of positive external electric field in the MSH/WSN Schottky-junction. Under the action of negative external electric field, the MSH/WSN Schottky-junction can be modulated to realize the transition from the Schottky contact to the Ohmic contact. The large biaxial strain can also induce the MSH/WSN Schottky-junction to realize the transition between the p-type Schottky contact and the n-type Schottky contact. This work may provide theoretical guidance for the WSN semiconductor based Schottky functional devices and field-effect transistors.

Effects of electric field on Schottky barrier in graphene and hexagonal boron phosphide heterostructures

Two dimensional graphene-based van der Waals heterostructures have attracted the interest of various researchers due to their unique properties. Based on the contact between metal electrodes and two dimensional materials has a substantial impact on the performance of electronic devices. The interfacial performance and Schottky contact performance with graphene and hexagonal boron phosphide (h-BP) vdW heterostructures are investigated using density functional theory calculations. We investigated eight energy-stable stacking configurations of multilayer graphene and h-BP vdW heterostructures. The different configurations of the h-BP/graphene vdW heterostructures all exhibit n-type Schottky contacts. The band structure of the h-BP in the heterostructures can be modulated under the influence of an external electric field (E field ), thus effectively manipulating the Schottky barrier height (SBH). The n-type SBH increases with the increasing positive E field and eventually the contact transforms into an Ohmic contact, while the Schottky contact transition from n-type to p-type occurs under the negative E field . The data demonstrate that modulating the electronic properties of hexagonal boron phosphide/graphere (h-BP/Gr) vdW heterostructures with E field is a promising approach, which can control the transition from Schottky to Ohmic contacts. The results can provide theoretical support for the design of controlled Schottky nanoelectronic devices. • 2D h-BP/Gr vdW heterostructures possesses a low n-type Schottky barrier height (0.15 eV–0.18 eV). • The transformate heterostructures can be transformed from an n-type Schottky contact to a p-type Schottky contact, then to an Ohmic contact. • The SBH of h-BP/Gr vdW heterostructures can be effectively regulated by an external electric field. • As the number of graphene layers increases the external electric field required for Schottky transition decreases.

Regulation and control of Schottky barrier in graphene/MoSe<sub>2</sub> heteojuinction by asymmetric oxygen doping

Although graphene-based heterostructures exhibit excellent intrinsic properties for device scaling, fabricating low Schottky barrier is still a great challenge to the electrical transport behaviors of nanoelectronic devices. Exploring excellent materials for electronic devices are a research hotspot at present. Graphene not only exhibits excellent physical strength and specific surface area, but also presents high carrier mobility and thermal conductivity. Therefore, graphene has been developed in many fields such as energy, catalysis, etc. However, graphene is a special material with zero band gap, and its electrons and holes are easy to compound, which seriously hinders its development in the applications of electronic and optoelectronic devices. Two-dimensional transition metal dichalcogenides (TMDs) have the advantages of controllable band gap properties, which makes them have a good development in logic circuits and photodetectors. As one of TMD<sub>S</sub>, MoSe<sub>2</sub> possesses the advantages of narrower band gap, better electron hole separation and stronger oxidation resistance in the environment. Therefore, the design of graphene and MoSe<sub>2</sub> heterostructures is an ideal choice for a new generation of nanoelectronic devices. Here, we investigate systematically the effects of asymmetric O doping on the electronic properties and Schottky barrier of graphene/MoSe<sub>2(1–<i>x</i>)</sub>O<sub>2<i>x</i></sub> heterostructure for the first time by first-principles calculations incorporating semiempirical dispersion-correction scheme. The results indicate that graphene and MoSe<sub>2</sub> monolayer can form a stable van der Waals heterostructure with preserving their own intrinsic properties. In addition, an n-type schottky contact with a barrier height of 0.558 eV is obtained. Further, it is found that the type and the height of the Schottky barrier can be controlled by changing the concentration and sites of the O dopant at interface. By increasing the concentration of the O dopant inside the interface, the transition from an n-type Schottky contact to an Ohmic contact can be realized, and a low n-type Schottky barrier is gained with increasing the concentration of the O dopant outside the interface for highly efficient charge transfer. The barrier height of heterostructure decreases from 0.558 eV to 0.112 eV when the O dopant is doped on the outer interface. Finally, as a complement to previous results, it is confirmed that the redistribution of interfacial charges leads the Fermi level to shift, and thus determining the type and the height of Schottky barrier. This study may provide theoretical guidance for designing and manufacturing the MoSe<sub>2</sub>-based nano field effect transistors.

Influence of the interface structure and strain on the rectification performance of lateral MoS2/graphene heterostructure devices.

We systematically study the influence of interface configuration and strain on the electronic and transport properties of lateral MoS2/graphene heterostructures by first-principles calculations and quantum transport simulations. We first identify the favorable heterostructure configurations with C-S and/or C-Mo bonds at the interfaces. Strain can be applied to graphene or MoS2 and would not change the relative stabilities of different heterostructures. Band alignment calculations show that all the lateral heterostructures have n-type Schottky contacts. The current-voltage characteristics of the lateral MoS2/graphene heterostructure diodes exhibit good rectification performance. Too strong and too weak interface interactions do not benefit electronic transport. The MoS2/graphene heterostructures with moderate C-S bonds at the interface have larger currents through the junctions than those with C-Mo bonds at the interface. The maximal rectification ratio of the lateral diode with strain applied to MoS2 can reach up to 105. With strain applied to graphene, the currents through the heterostructures can increase by 1-2 orders of magnitude due to the reduced Schottky barrier heights at the interface, but the rectification ratio is reduced with a maximal value of 104. Our calculations can serve as a theoretical guide to design rectifier and diode devices based on two-dimensional lateral heterostructures.

First-Principles Study of Defected Single Layer Hexagonal Boron-Nitride (h-BN)

The novel properties of pristine h-BN, oxygen (O) atom impurity defects in h-BN (h-B(N-O) and h-(B-O)N), one boron (1B) atom vacancy defect in h-BN (h-BN_1B) and one nitrogen (1N) atom vacancy defect in h-BN (h-BN_1N) materials are investigated by spin-polarized density functional theory (DFT) using computational tool Quantum ESPRESSO. We found that they are stable materials. From the band structure calculations, we found that all the considered systems are wide bandgap materials. The bandgap energy of pristine h-BN, impurity defects h-B(N-O) and h-(B-O)N, and vacancy defects h-BN_1B and h-BN_1Nmaterials have values 4.98 eV, 4.19 eV& 2.47 eV,and 4.84 eV& 3.62 eV respectively. Also, it is found that h-B(N-O) and h-BN_1N materials have n-type Schottky contact while h-(B-O)N and h-BN_1B materials have p-type Schottky contact. From the analysis ofdensity of states (DOS) and partial density of states (PDOS) calculations, we found that non-magnetic pristine h-BN changes to magnetic h-B(N-O) andh-(B-O)N materials due to presence of impurity defects,and h-BN_1B andh-BN_1N materials due to presence of vacancy defects. Magnetic moments of h-B(N-O), h-(B-O)N, h-BN_1B and h-BN_1N materials are 1.00 µB/cell, 0.94 µB/cell, 3.00 µB/cell and 1.00 µB/cell respectively. They are obtained due to unpaired up and down spins state of electrons in 2p orbital of B and N atoms in the structures.

Electronic properties and tunable Schottky barrier of non-Janus MoSSe/graphene heterostructures

We investigate the stability and electronic properties of van der Waals junctions composed with graphene and non-Janus MoSSe in comparison with graphene/Janus MoSSe configuration, and furthermore explore its Schottky barrier as well as the effect of external electric field. Based on first-principles calculations, we compare the interlayer distance and binding energy between them. It is found that with the adhesion of graphene, the less-stable Janus MoSSe becomes the most stable configuration. The graphene/non-Janus MoSSe configuration has the minimum interlayer distance, and the weak vdW interactions indicates the preservation of unique electronic properties in both two materials. An n-type Schottky contact with the Schottky barrier height (SBH) of 0.38 eV is formed at the equilibrium state for graphene/non-Janus MoSSe, while the n-type SBH for two configurations of graphene/Janus MoSSe is 0.67 and 0.10 eV, respectively. With the application of an external electric field perpendicularly to the surface, not only the Schottky barrier height but also the transition of n-type and p-type Schottky contacts as well as Ohmic contacts can be modulated within a relatively small electric field strength. This property distinguishes graphene/non-Janus MoSSe from graphene/Janus MoSSe configuration, and provides great potential for applications in optoelectronic and nanoelectronic and devices.

Tunable contacts and device performances in graphene/group-III monochalcogenides MX (M = In, Ga; X = S, Se) van der Waals heterostructures

Graphene-based van der Waals (vdW) heterostructures have attracted extensive attention for applications like nanoelectronics. The graphene and group-III monochalcogenide (MX, M = In and Ga and X = S and Se) heterostructures were established herein, and the electronic properties were investigated by the first-principles calculation. These heterostructures form an n-type Schottky contact at the interface and the Schottky barrier height can be modulated by the external strain. With graphene as electrodes, the device performances of the 9 nm MX metal-oxide-semiconductor FETs (MOSFETs) are investigated. Based on the computed tunneling probability and transfer characteristics, the GaSe MOSFET with a graphene electrode stands out with the highest tunneling probability and largest on-off ratio. We believe these results can provide physical insights into designing and fabricating devices based on the graphene and group-III monochalcogenide heterostructures.

Substitutional doping at S site of MoS2/G heterostructure: The influence on voltage-current and electronic characteristics

The effect of substitutional doping at S site on the electronic properties of MoS 2 /Graphene (MoS 2 /G) was studied by First-principles calculations. Through the analysis on the energy band and density of states of MoS 2 /Graphene, it was found that the S vacancy in MoS 2 monolayer caused the Dirac point shifted, and produced the defect energy levels at the Dirac point, which hindered the carrier transmission. Periods II-IV elements were doped at the S vacancy to improve the electronic properties and performance of MoS 2 /G. The calculated results show that the charge transfer of MoS 2 /G was greatly enhanced by the doping of N, P and As atoms. The current-voltage characteristic of N, P and As-doped G/MoS 2 /MoS 2 /G structure has higher drive-current and stable OFF-state current which can reduce device current consumption. For O-doped and Se-doped MoS 2 /G heterostructures , there is no impurity level introduced, and the Schottky barrier height increase (decrease) with the increase (decrease) of the biaxial strain, meantime the p-type Schottky contact , n-type Schottky contact and Ohmic contact characteristic can be converted mutually by adjusting biaxial strain or vertical external force. Our findings will be of great guiding significance for the designing of interface devices and explorations on nano-electronics. • The passing carriers were trapped by S vacancy in MoS 2 /G heterostrcture. • The current-voltage characteristics of N-doped, P-doped and As-doped of G/MoS 2 /MoS 2 /G were improved. • The contact type of O-doped, Se-doped and undoped MoS 2 /G can be converted by adjusting external force.

Tuning Schottky Barrier and Contact Type of Metal–Semiconductor in Ti3C2T2/MoS2 (T = F, O, OH) by Strain: A First-Principles Study

MXene is widely used for electrode materials. However, the interfacial resistance between metal and semiconductor affects the device performance. The strain has become an effective strategy to improve interfacial properties. With the aim of revealing the interface mechanism and improving device performance, we use the first-principles calculation to investigate the electronic properties of Ti3C2T2/MoS2 (T = F, O, OH) junctions and the effect of strain on the interfaces. The calculations show weak forces between Ti3C2T2 and MoS2 monolayer, and the interfacial interaction decreases in the order of Ti3C2(OH)2/MoS2, Ti3C2F2/MoS2, and Ti3C2O2/MoS2. Ti3C2F2/MoS2 exhibits a p-type Schottky barrier with 0.51 eV and Ti3C2O2/MoS2 shows a p-type Schottky barrier with 0.12 eV, whereas an n-type ohmic contact occurs in Ti3C2(OH)2/MoS2. Interestingly, the contact types and Schottky barrier height in the Ti3C2F2/MoS2 and Ti3C2O2/MoS2 junctions can be tuned by biaxial strain in plane, which shows a transition from a p-type Schottky contact to an n-type Schottky contact and then to an n-type ohmic contact. An ohmic contact is maintained in Ti3C2(OH)2/MoS2. Furthermore, the tunneling probability (TP) of Ti3C2(OH)2/MoS2 with 27.34% drops sharply, although the TP of Ti3C2F2/MoS2 and Ti3C2O2/MoS2 gradually increases with increasing strain. The controllable contact type and barrier in the Ti3C2T2/MoS2 junction make it a promising candidate for high-performance electronic devices.

Structural, Electronic and Magnetic Properties of Impurities Defected Graphene/MoS2 Van Der Waals Heterostructure: First-principles Study

Two-dimensional (2D) pristine and defected van der Waals (vdW) heterostructure (HS) materials open up fortune in nanoelectronic and optoelectronic devices. So, they are compatible for designing in the fields of device applications. In the present work, we studied structural, electronic and magnetic properties of vdW (HS) graphene/MoS2 ((HS)G/MoS2), Nb impurity defect in vdW (HS) graphene/MoS2 (Nb-(HS)G/MoS2), and Tc impurity defect in vdW (HS) graphene/MoS2 (Tc-(HS)G/MoS2) materials by using spin-polarized DFT-D2 method. We examined the structure of these materials, and found that they are stable. Based on band structure analysis, we found that (HS)G/MoS2, Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 have metallic characteristics. Also, (HS)G/MoS2 and Tc-(HS)G/MoS2 materials have n-type Schottky contact, while Nb-(HS)G/MoS2 material has p-type Schottky contact. To understand the magnetic properties of materials, we have used DoS, IDoS and PDoS calculations. We found that (HS)G/MoS2 is a non-magnetic material, but Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 are magnetic materials. Magnetic moment of Nb-(HS)G/MoS2 and Tc-(HS)G/MoS2 materials are -0.24 μB/cell and +0.07μB/cell values respectively from DoS/PDoS calculations, and 0.26 μB/cell and 0.08μB/cell values respectively from IDoS calculations. Up-spin and down-spin states of electrons in 2p orbital of C atoms, 3p orbital of S atoms, 4d orbital of Mo atoms, 4d orbital of Tc atom in Tc-(HS)G/MoS2, and 2p orbital of C atoms, 3p orbital of S atoms, 4p & 4d orbitals of Mo atoms, 4p & 4d orbitals of Nb atom in Nb-(HS)G/MoS2 have major contribution for the development of magnetic moment.

Effects of vertical strain and electric field on the electronic properties and interface contact of graphene/InP vdW heterostructure

The graphene/InP Schottky heterojunction solar cells, possessing a great significance in special applications of space optoelectronic devices, have been realized experimentally, however, the mechanism of the contact nature is lack. In this contribution, using first-principles calculation, we investigate the electronic properties and interface contacts of heterostructures through varying interlayer spacing and applying external electric fields. Our results indicate that graphene/InP is a typical vdW heterostructure with an equilibrium layer spacing of 3.65 Å. A small band gap of approximately 67 meV is opened, indicating a promising prospect concerning optoelectronic devices. Meanwhile, the formation of built-in electric field significantly promotes the separation of photogenerated electron-hole pairs. Additionally, the p-type Schottky contact with 0.04 eV p-type and 2.03 eV n-type SBH, respectively, is formed in the most stable configuration. Importantly, when the interlayer distance decreases below 3.6 Å, the heterostructure changes from p-type Schottky contact to p-type Ohmic contact. When exerting a negative electric field, the heterostructure belongs to p-type Ohmic contact. As the electric field increases to 0.55 V/Å, the transition from p-type to n-type Schottky contact is observed. These findings may be expected to have significant guiding value for design and fabrication of nano-devices based on graphene/InP vdW heterostructure.

Effects of vertical strain and electrical field on electronic properties and Schottky contact of graphene/MoSe2 heterojunction

Fabricating a low Schottky barrier is still a great challenge in electrical transport behavior of nano field effect transistors (FETs). To settle this problem, the electronic properties and Schottky contact of the graphene/MoSe2 heterojunction employing various vertical strains and external electrical fields are investigated with density functional theory (DFT) to obtain low Schottky barrier. Our calculation illustrates that in the graphene/MoSe2 heterojunction, the intrinsic electronic properties of components are well preserved owing to the weak van der Waals (vdW) mutual interaction between graphene and MoSe2 monolayer. Furthermore, there is an n-type Schottky contact formed with an n-type Schottky barrier height (SBH) of 0.56 eV at the interface of graphene/MoSe2 heterojunction. It is worth noting that the type and the height of Schottky barrier are susceptible to the external electrical field or strain employed perpendicularly to the graphene/MoSe2 heterojunction. And the SBH of the interface can be reduced by tuning the interlayer distance (d) or the electrical field intensity (E). Moreover, Schottky contact transforms from n-type to p-type at d = 3.22 Å or E = +0.08 V/Å. Additionally, the Ohmic contact occurs when the magnitude of positive or negative electrical field is larger than 0.40 V/Å, respectively. Additionally, the heterojunction maintaining high carrier mobility is inferred from the effective masses of electron and hole, namely, 0.074 m0 and 0.055 m0, respectively. Our study may put forward effective strategies to enhance the electronic performance of MoSe2-based vdW heterojunction FETs.