Heterojunction semiconductor structure, preparation method thereof, photoelectric sensing device and application

Abstract

The invention discloses a heterojunction semiconductor structure, a preparation method thereof, a photoelectric sensing device and application. The heterojunction semiconductor structure comprises p-type GaN, an interface insertion layer and a graphene layer which are in contact in sequence, the interface insertion layer is composed of h-BN layers, and the number of the h-BN layers in the interface insertion layer is 1-5. According to the graphene / h-BN / p-GaN heterojunction-based high-performance ultraviolet photoelectric detector provided by the invention, accurate control of physical properties of an interface is realized through cooperative regulation and control of the number of h-BN layers and the p-type GaN substrate, and the ultraviolet detection performance of the device is remarkably improved; the device has the advantages of low dark current, high response speed, good environmental stability and the like, and is suitable for ultraviolet detection application in severe environments such as high temperature and high irradiation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor optoelectronic devices, and in particular to a heterojunction semiconductor structure, a preparation method thereof, an optoelectronic sensing device and application. BACKGROUND

[0002] Ultraviolet photodetectors have wide application prospects in the fields of military, communication, environmental monitoring, biochemical sensing, etc. Gallium nitride (GaN) as a kind of direct wide bandgap semiconductor (Eg = 3.4 eV) is an ideal material for preparing ultraviolet photodetectors. However, the traditional metal / GaN Schottky junction detector has problems such as high dark current, slow response speed, and low quantum efficiency.

[0003] Graphene is widely used to construct high-performance photodetectors due to its high carrier mobility, wide-spectrum absorption, and ultrafast response. However, the heterojunction formed by direct contact between graphene and GaN has problems such as interface charge disorder transfer and uncontrollable barrier height, which seriously restricts the improvement of device performance.

[0004] In recent years, researchers have tried to insert hexagonal boron nitride (h-BN) as an interface layer between graphene and GaN to modulate the interface physical properties. However, existing researches mostly focus on n-type GaN substrates, and there is little research on p-type GaN substrates. Moreover, there is a lack of systematic understanding of the mechanism of layer number (especially 1-5 layers) of h-BN in modulating the interface properties, and the unique advantages of h-BN interface intercalation have not been fully utilized. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a heterojunction semiconductor structure, a preparation method thereof, an optoelectronic sensing device and application.

[0006] To achieve the aforementioned application purposes, the technical solutions adopted by the present application include:

[0007] In a first aspect, the present application provides a heterojunction semiconductor structure, which comprises p-type GaN, an interface insertion layer and a graphene layer in contact with each other in sequence, the interface insertion layer is composed of an h-BN layer, and the number of the h-BN layer in the interface insertion layer is 1-5.

[0008] In a second aspect, the present application further provides a preparation method of a heterojunction semiconductor structure, which comprises:

[0009] providing a p-type GaN substrate;

[0010] using a first polymer film to carry the h-BN layer, so that the h-BN layer is attached to the p-type GaN substrate;

[0011] removing the first polymer film to obtain a p-type GaN / h-BN combination, and optionally repeating the covering of several layers of h-BN layers;

[0012] using a second polymer film to carry the graphene layer, so that the graphene layer is attached to the h-BN layer of the p-type GaN / h-BN combination;

[0013] removing the second polymer film to obtain a heterojunction semiconductor structure.

[0014] In a third aspect, the present application also provides a photoelectric sensing device, which comprises the above-mentioned heterojunction semiconductor structure, a first electrode and a second electrode; the first electrode is in contact with the p-type GaN in the heterojunction semiconductor structure, and the second electrode is in contact with the graphene layer in the heterojunction semiconductor structure.

[0015] In a fourth aspect, the present application also provides the application of the above-mentioned photoelectric sensing device in ultraviolet light detection, flame sensing, ultraviolet communication or biochemical detection.

[0016] Based on the above technical solution, compared with the prior art, the beneficial effects of the present application at least include:

[0017] The present application provides a high-performance ultraviolet photodetector based on graphene / h-BN / p-GaN heterojunction, which realizes accurate control of the interface physical properties through the synergistic regulation of the number of h-BN layers and the p-type GaN substrate, significantly improves the ultraviolet detection performance of the device, and makes the device have the advantages of low dark current, fast response speed, good environmental stability and the like, and is suitable for ultraviolet detection applications in harsh environments such as high temperature and high irradiation.

[0018] The above description is only a summary of the technical solutions of the present application, in order to enable those skilled in the art to more clearly understand the technical means of the present application, and to implement the content of the description, the following is a preferred embodiment of the present application and the detailed description of the drawings as follows. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a preparation and test process schematic diagram of the heterojunction semiconductor structure provided by a typical embodiment of the present application;

[0020] Figure 2 is a potential barrier height and threshold voltage change graph of the n-type heterojunction semiconductor structure under different numbers of h-BN layers provided by a typical embodiment of the present application;

[0021] Figure 3 is a potential barrier height and threshold voltage change graph of the p-type heterojunction semiconductor structure under different numbers of h-BN layers provided by a typical embodiment of the present application;

[0022] Figure 4is a typical embodiment of the present application provides the ideal coefficient and the change graph of series resistance of the heterojunction of the n-type heterojunction semiconductor structure under different h-BN layers;

[0023] Figure 5 is a typical embodiment of the present application provides the ideal coefficient and the change graph of series resistance of the heterojunction of the p-type heterojunction semiconductor structure under different h-BN layers;

[0024] Figure 6 is a typical embodiment of the present application provides the change graph of the depletion region width and the maximum electric field intensity of the n-type heterojunction semiconductor structure under different h-BN layers;

[0025] Figure 7 is a typical embodiment of the present application provides the change graph of the depletion region width and the maximum electric field intensity of the p-type heterojunction semiconductor structure under different h-BN layers;

[0026] Figure 8 is a typical embodiment of the present application provides the change graph of the charge density of the n-type heterojunction semiconductor structure under different h-BN layers;

[0027] Figure 9 is a typical embodiment of the present application provides the change graph of the charge density of the p-type heterojunction semiconductor structure under different h-BN layers;

[0028] Figure 10 is a typical embodiment of the present application provides the change graph of the energy level movement of the n-type heterojunction semiconductor structure under different h-BN layers;

[0029] Figure 11 is a typical embodiment of the present application provides the change graph of the energy level movement of the p-type heterojunction semiconductor structure under different h-BN layers;

[0030] Figure 12 is a typical embodiment of the present application provides the change graph of the built-in potential of the n-type heterojunction semiconductor structure under different h-BN layers;

[0031] Figure 13 is a typical embodiment of the present application provides the change graph of the built-in potential of the p-type heterojunction semiconductor structure under different h-BN layers. DETAILED DESCRIPTION

[0032] It is well known that the formation of an interface is essentially a process in which the band structure and electronic properties of the two contacting materials are coupled to each other. The doping type of the GaN substrate strictly controls its Fermi level, surface states and band bending, thus directly modulating the interface charge transfer and energy level alignment in the heterojunction, which ultimately determines the electrical performance of the device. Zhong et al. demonstrated that n-GaN and p-GaN induce opposite Fermi level shifts with respect to the Dirac point in SLG, thus modulating the carrier injection. Herman et al. observed a similar Fermi level position (about 0.9 eV below the conduction band of GaN) at the SLG / n-GaN interface.

[0033] However, the published studies show three main limitations: (1) the systematic modulation mechanism of the substrate doping type from the microscopic interface properties to the macroscopic electrical transport has not been thoroughly investigated; (2) the doping-dependent interface charge transfer dynamics mediated by the surface states and pinning effect, which ultimately determines the rectifying or ohmic behavior of the heterojunction, is currently unclear; (3) the potential synergistic effect between the substrate doping type and the thickness of the h-BN interlayer may not have been fully explored.

[0034] Therefore, understanding the synergistic effect of GaN substrate doping and h-BN thickness on the interface physics and electrical properties of SLG / GaN heterostructures is crucial for optimizing device performance and realizing new functional applications.

[0035] In view of the deficiencies in the prior art, the present inventors have long studied and practiced to come up with the technical solution of the present application. The technical solution, its implementation process and principles will be further explained as follows.

[0036] The present application specifically relates to a kind of ultraviolet photodetector based on two-dimensional material / three-dimensional semiconductor heterojunction, especially to a kind of van der Waals heterojunction device represented by graphene (SLG) / hexagonal boron nitride (h-BN) / p-type gallium nitride (p-GaN). Many specific details are set forth in the following description in order to fully understand the present application, however, the present application can also be implemented in other ways different from those described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0037] Moreover, relational terms such as "first" and "second", and the like can merely be used to distinguish one entity or methodological step from another, without necessarily requiring or implying any such actual relationship or order between such entities or methodological steps.

[0038] The present application provides an ultraviolet photodetector based on graphene / h-BN / p-GaN van der Waals heterojunction and a preparation method thereof to overcome the deficiencies of the prior art. The device utilizes the synergistic regulation effect of the h-BN interlayer and the p-type GaN substrate to significantly improve the ultraviolet detection performance of the device.

[0039] For the above purposes, the embodiments of the present application provide a heterojunction semiconductor structure, which comprises a p-type GaN, an interface interlayer and a graphene layer in contact with each other in sequence, the interface interlayer is composed of an h-BN layer, and the number of the h-BN layer in the interface interlayer is 1-5.

[0040] As a typical application example, the preferred embodiments of the present application take p-type GaN as the substrate, transfer 1-5 layers of h-BN and a single layer of graphene (SLG) on the p-GaN in sequence, and then prepare metal electrodes on the graphene and the p-GaN respectively to form a symmetric or asymmetric electrode structure.

[0041] In some embodiments, the number of the h-BN layer in the interface interlayer makes the Fermi level of the graphene layer approach the Dirac point.

[0042] In some embodiments, the number of the h-BN layer in the interface interlayer is selected to be 1-3. More preferably, it is 2 layers. The number of 2 layers of interlayers generally exhibits excellent modulation performance in most graphene / h-BN / p-GaN van der Waals heterojunctions, but is not limited thereto. For different doping concentrations of p-GaN, the optimal number of interlayers may vary.

[0043] In some embodiments, the graphene layer is selected from a single layer of graphene.

[0044] In the embodiments of the present application, as the thickness of the h-BN layer increases, the Fermi level of the graphene gradually approaches the Dirac point, which can be regulated to the desired position of the graphene Fermi level by the number of layers of the oligolayer h-BN (equivalent to the present application also provides a Fermi level regulation method of graphene / h-BN / p-GaN van der Waals heterojunction). Because different Fermi level positions mean the doping degree of graphene by GaN, the closer to the Dirac point, the less the graphene is doped by the p-type GaN, and most of the electric charges transferred from the p-type GaN to the graphene are hindered by boron nitride; without the h-BN interlayer, the graphene is in direct contact with the p-GaN. Due to the difference in work function, significant charge transfer occurs, resulting in strong p-type doping of the graphene (the Fermi level is far from the Dirac point), which forms a high-resistance Schottky barrier between the graphene and the p-GaN, hindering the injection of holes from the graphene electrode to the p-GaN active layer, and reducing the light emission / photoelectric conversion efficiency of the device.

[0045] As a typical example, when the thickness of h-BN is thinned to a suitable degree (for example, 1-3 layers), it can effectively prevent the direct charge transfer between graphene and p-GaN, return the Fermi level of graphene to the vicinity of the Dirac point (reduce doping, tend to be intrinsic), greatly reduce the contact resistance, and at the same time, it is thin enough to allow holes to be injected into p-GaN by quantum tunneling effect, meeting the device conduction requirements.

[0046] Although the insertion of h-BN can regulate the Fermi level of graphene on both n-GaN and p-GaN, some phenomena observed on graphene / h-BN / p-GaN are not observed on n-GaN, such as the depletion area of the heterojunction constructed on p-GAN is smaller, but the built-in electric field strength is higher, which is not observed in n-GaN, and the regularity of the depletion area and the built-in electric field strength is just the opposite.

[0047] The modulation regularity of graphene / h-BN / p-GaN is more friendly to the production of optoelectronic devices, because the larger built-in electric field has higher and faster light-generated carrier separation efficiency, and the optoelectronic detection will show the advantages of higher photoelectric conversion efficiency and greater responsivity.

[0048] Therefore, the main technical contribution of the technical scheme provided by the present application is that, based on the typical regularity different from the n-GaN-graphene heterojunction discovered by the inventors of the present application, the intercalation-doping modulation regularity observed on graphene / h-BN / p-GaN can make progress in photoelectric conversion detection.

[0049] In order to obtain the above-mentioned device, the embodiment of the present application further provides a preparation method of a heterojunction semiconductor structure, which comprises the following steps:

[0050] providing a p-type GaN substrate;

[0051] carrying an h-BN layer by using a first polymer film, and making the h-BN layer face and attach to the p-type GaN substrate;

[0052] removing the first polymer film to obtain a p-type GaN / h-BN combination, and optionally repeating the covering of several layers of h-BN layers;

[0053] carrying a graphene layer by using a second polymer film, and making the graphene layer face and attach to the h-BN layer of the p-type GaN / h-BN combination;

[0054] removing the second polymer film to obtain a heterojunction semiconductor structure.

[0055] In some embodiments, the preparation method can specifically comprise the following steps:

[0056] The h-BN layer is grown using a first metal substrate;

[0057] The first polymer film is formed by coating the surface of the h-BN layer;

[0058] The first metal substrate is removed by etching to obtain a combination of the first polymer film and the h-BN layer;

[0059] In some implementation schemes, the following steps may also be included:

[0060] The graphene layer is grown using a second metal substrate;

[0061] The second polymer film is formed by coating the surface of the graphene layer;

[0062] The second metal substrate is removed by etching to obtain the combination of the second polymer film and the graphene layer.

[0063] In some embodiments, the method for removing the first polymer film or the second polymer film specifically includes the following process:

[0064] The first or second polymer film is removed by dissolving it with an organic solvent;

[0065] The residual adhesive in the first or second polymer film is then removed by annealing.

[0066] As a typical example, such as Figure 1 As shown, SLG and monolayer h-BN can be grown on copper foil using chemical vapor deposition (CVD); then h-BN and SLG can be sequentially transferred to a surface-treated p-GaN substrate using a wet transfer technique; and finally, the PMMA support layer used in the transfer process can be removed by a thermal annealing process.

[0067] For this semiconductor structure, a probe station can be used for testing, or photolithography can be used to fabricate electrodes to form usable application devices.

[0068] The doping of GaN layers and the insertion of h-BN layers exhibit a synergistic control mechanism: increasing the number of h-BN layers (1-5 layers) effectively suppresses interface charge transfer and increases the barrier height (qφ). Bp0 This reduces dark current; p-type GaN substrates have a higher carrier concentration (e.g., 3.340 × 10⁻⁶) compared to n-type GaN. 16 cm -3 vs. 7.697×10 15 cm -3 This results in a narrower depletion region and a stronger built-in electric field (|E). maxThe insertion of h-BN gradually approaches the Fermi level of graphene to the Dirac point, and reduces the interface state trap charge density (Q i ), and improves the carrier transport efficiency.

[0069] Therefore, the semiconductor structure provided by the present application has the following progressive effects.

[0070] 1. Low dark current and high rectification ratio: the insertion of the h-BN layer significantly suppresses the tunneling current under reverse bias, improving the rectification characteristics of the device.

[0071] 2. Strong built-in electric field and efficient carrier separation: the narrow depletion region (ω is small) and strong built-in electric field (|E max | is large) formed by the p-GaN substrate help to quickly separate and collect photo-generated carriers.

[0072] 3. Controllable interface physical properties: the number of h-BN layers can accurately control parameters such as barrier height, built-in potential, and charge transfer, providing flexible means for device performance optimization.

[0073] The present application also provides a photoelectric sensing device, which comprises the heterojunction semiconductor structure provided by any of the above embodiments, a first electrode and a second electrode; the first electrode is in contact with the p-type GaN in the heterojunction semiconductor structure, and the second electrode is in contact with the graphene layer in the heterojunction semiconductor structure.

[0074] Based on the above semiconductor structure, the device provided by the present application is particularly suitable for ultraviolet photodetection: the device has high absorption, fast response, low noise, etc. in the ultraviolet waveband, and is particularly suitable for ultraviolet detection applications in harsh environments such as high temperature and high radiation.

[0075] Therefore, the present application also provides the application of the above photoelectric sensing device in ultraviolet light detection, flame sensing, ultraviolet communication or biochemical detection.

[0076] In some embodiments, the operating temperature of the photoelectric sensing device is above 150°C.

[0077] The technical solutions of the present application are further described in detail below through several embodiments in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present application, and do not limit the scope of the present application.

[0078] Embodiment 1

[0079] This embodiment illustrates the preparation and characterization process of graphene / h-BN / p-GaN ultraviolet photodetector, as shown below.

[0080] Material preparation:

[0081] p-type GaN substrate (carrier concentration: 3.340 x 1018cm-3); CVD grown monolayer graphene and monolayer h-BN (prepared by Shanghai Angew Technology Co., Ltd.). 16 cm -3 );CVD grown monolayer graphene and monolayer h-BN (prepared by Shanghai Angew Technology Co., Ltd.).

[0082] Substrate processing:

[0083] Ultrasonic cleaning with deionized water, acetone, and anhydrous ethanol for 15 minutes each;

[0084] Immersion in 85% hydrochloric acid and 5 mol / L sodium hydroxide solution for 2 minutes each to remove the surface oxide layer;

[0085] Immersion in 20% ammonium sulfide solution for 1 minute to saturate the surface dangling bonds.

[0086] Heterojunction preparation:

[0087] One layer of h-BN was transferred to the surface of p-GaN using wet transfer technology, and then monolayer graphene was transferred onto the h-BN; soaking in 50°C acetone for 120 minutes to remove PMMA; annealing at 450°C for 2 hours in Ar / H2 atmosphere to remove residual PMMA.

[0088] Electrode preparation:

[0089] Indium ball electrodes and tungsten probe electrodes were prepared on graphene and p-GaN respectively using a probe station.

[0090] Performance testing:

[0091] The I-V characteristics of the device were measured using a probe station (voltage range: -2V to 2V);

[0092] The number of layers of the material was confirmed using a 532 nm laser Raman spectrometer;

[0093] The interface contact was observed using a scanning electron microscope (SEM).

[0094] Comparative Example 1

[0095] This comparative example is generally the same as Example 1, with the main difference being that the p-type GaN substrate is replaced by an n-type GaN substrate.

[0096] Example 2

[0097] This example compares the performance of devices with different numbers of h-BN layers by changing the number of layers, as shown below:

[0098] SLG / h-BN / p (or n)-GaN devices with 0, 1, 2, 3, 4, and 5 layers of h-BN were prepared respectively, and their electrical properties were tested. The results showed that:

[0099] As the number of h-BN layers increases, the barrier height of the SLG / h-BN / p-GaN device ( The threshold voltage (Vt) gradually increases from 0.519 eV to 0.832 eV. h The reverse dark current decreased significantly from 0.017V to 0.095V, and the rectification ratio increased by more than an order of magnitude; the built-in electric field strength (|E) max |) Remains at a high level (5.8×10 4 ~9.3×10 4 The V / cm ratio is significantly better than that of devices with the same structure on an n-type substrate.

[0100] The above implementation examples used chemical vapor deposition (CVD) to transfer SLG or h-BN grown on copper foil onto n-GaN and p-GaN substrates, fabricating SLG / h-BN / n-GaN and SLG / h-BN / p-GaN van der Waals heterojunctions with 0-5 layers of h-BN. The structure and electrical properties of the heterojunctions were characterized and tested using Raman spectroscopy, scanning electron microscopy, and probe microanalysis. Based on traditional Schottky theory and the established SLG / GaN contact model, the interface physical properties were calculated and analyzed. By introducing different numbers of h-BN layers (1-5 layers) at the contact interface of the SLG / GaN heterojunction and changing the doping type of the GaN substrate (n-type and p-type), the synergistic regulation and mechanism of h-BN insertion layer thickness and substrate doping type on the electrical properties and interface physical properties (such as charge transfer, barrier height, and built-in potential) of the heterojunction were studied. Therefore, this study not only provides insights into the interface characteristics and electrical properties of two-dimensional materials / wide bandgap semiconductors, but also offers experimental evidence for the precise control of heterojunction interface engineering and the improvement of device optoelectronic performance.

[0101] The specific test results for the relevant parameters are as follows: Figures 2-13 As shown, the relevant parameters of n-type and p-type devices vary with the number of intercalation layers.

[0102] In the diagram, E vac This indicates the vacuum energy level. and χ and E are the work functions of graphene and GaN before they come into contact, respectively. g These represent the electron affinity and band gap of GaN, respectively. F，gra and E F，s These are the Fermi levels of graphene and GaN before they come into contact. E c and E v These represent the bottom energy level of the conduction band and the top energy level of the valence band in GaN, respectively. E represents the bottom conduction band energy level of n-GaN. c With Fermi level E F，senergy level difference between E v is the valence band maximum of p-GaN. F，s is the energy level difference between and are the work functions of graphene and GaN after contact, respectively. and are the Fermi levels of graphene and GaN after contact, respectively. and represent the interfacial distance and the potential difference across the interface layer, respectively. and are the barrier heights of n-GaN and p-GaN, respectively. is the built-in potential of GaN. s and gra represent the charge density in the depletion region of GaN and the charge density transferred from GaN to graphene, respectively. it and represent the interfacial trap density and the midgap energy level of the GaN surface, respectively. i represents the density of the interface state trap charge. th represents the threshold voltage. η represents the ideality factor.

[0103] The barrier height, built-in potential, and transferred charge of SLG / h-BN / n-GaN and SLG / h-BN / p-GaN junctions with 0-5 layers of h-BN are calculated and analyzed by a theoretical model. Among them, η and s are obtained by fitting the seven I-V measurements shown in the figure with a thermionic emission model. As the thickness of the h-BN layer increases, the barrier height (V or ), V th , η, R s , ω, and |E max | of SLG / h-BN / n-GaN and SLG / h-BN / p-GaN junctions show a gradually increasing trend. The calculated values of and trends are related to the current increase amplitude in SLG / h-BN / n-GaN and SLG / h-BN / p-GaN junctions in the figure: and are larger, the corresponding current increase amplitude decreases with the increase of voltage. In addition, higher and hinder carrier injection and require a larger threshold voltage V thAs compensation, referencing known NBTI mechanisms, increasing the number of inserted h-BN layers may introduce more interface defects (e.g., stacking faults and dangling bonds), potentially increasing V. th (Similar to P-channel metal-oxide-semiconductor (PMOS) devices, V) th The increase is caused by Si-H bond breaking and enhanced interface trap charge density. The variation in the ideality factor η and series resistance R... s This is derived from the dV / dlnI-I curve. With increasing h-BN thickness, the IV characteristic of the heterojunction exhibits a greater deviation from the ideal (higher η), which may stem from enhanced interfacial recombination. The h-BN interlayer may alter the interfacial state or introduce recombination centers, thereby amplifying the recombination rate at the SLG / GaN interface and thus increasing η. Furthermore, with the same number of h-BN layers, the series resistance R of the SLG / h-BN / p-GaN junction... s The electric field strength is higher than that of the SLG / h-BN / n-GaN junction, which may be related to the resistivity and doping type of the GaN substrate material. Since the electric field strength E varies linearly with the depletion region width ω, only the maximum electric field strength |E| generated within the depletion region needs to be considered. max The change in |E| was observed. It was observed that ω in SLG / h-BN / n-GaN heterojunctions with different numbers of h-BN layers consistently exceeded that in SLG / h-BN / p-GaN heterojunctions. Interestingly, despite the depletion region |E| of the SLG / h-BN / n-GaN junction... max The n-GaN junction has a relatively large depletion region, but its depletion region is actually weaker than that of the SLG / h-BN / p-GaN junction. This observed phenomenon may be attributed to the difference in doping concentration (N0) between the n-GaN and p-GaN substrate materials. D The differences.

[0104] Q-type heterojunctions of SLG / h-BN / n-GaN and SLG / h-BN / p-GaN gra Q and The value of gradually decreases with increasing h-BN layer thickness (0-5 layers). As the h-BN thickness increases, the charge transfer amount Q... gra The decrease in (from n-GaN to SLG or from SLG to p-GaN) indicates that h-BN has a strong suppressive effect on interface charge transfer in both SLG / n-GaN and SLG / p-GaN junctions. The intrinsic interface states of semiconductors range from the intermediate performance level... and interface trap density D it The determination that the intermediate performance level and interface trap density are material-specific and independent of the contact metal is crucial. At a constant D... it Under these conditions, the height of the potential barrier ( or An increase in ) will reduce the semiconductor Fermi level. and The number of trap states that can be used between electron captures. Therefore, Q i The value is inversely proportional to the barrier height and gradually decreases with increasing h-BN layer height. i and Q gra They exhibit almost identical magnitudes and trends. This correlation suggests that charge transfer between GaN and graphene depends on the charge trapped in the surface states of GaN. In the neutral SLG prior to GaN contact, the Fermi level E F.gra Located at the Dirac point, the carrier density is negligible (n≈0). When in contact with GaN, the transferred charge Δn=Q gra / q will E F，gra Shift to a new equilibrium position This equilibrium position is directly controlled by Δn. The carrier transfer rate Δn (electrons from n-GaN or holes from p-GaN to SLG) decreases with increasing h-BN layer number, leading to Approaching the original Fermi level E F，gra And reduce Fermi level shift This trend indicates that in SLG / h-BN / n-GaN and SLG / h-BN / p-GaN junctions, with the addition of the h-BN layer, E of neutral SLG F，gra Directional convergence.

[0105] The calculation results also show that, with the increase of the h-BN layer thickness, the Q of the SLG / h-BN / n-GaN and SLG / h-BN / p-GaN heterojunctions increases. s , and Gradually decrease. Q s and The value of is proportional to the electric field E in the depletion region, thus exhibiting a consistent trend with increasing h-BN layer thickness. Furthermore, it was found that after inserting 2-h-BN, the total built-in potential of the SLG / h-BN / p-GaN heterojunction... and threshold voltage V th The growth trend has slowed significantly. Currently, it is difficult to theoretically explain why h-BN affects the heterostructure formed on p-GaN substrates. and V th The effect is thickness-dependent (2 layers), but this phenomenon was indeed observed.

[0106] Interestingly, in the SLG / h-BN / n-GaN heterojunction, The value increases with the number of h-BN layers, but the opposite is true in the SLG / h-BN / p-GaN junction. For the SLG / h-BN / n-GaN heterojunction, Change less than ,lead to and The difference in work function between them gradually increases. Therefore, It increases with increasing h-BN thickness. Conversely, in the SLG / h-BN / p-GaN junction, Change less than ,and and The difference between them decreases as the h-BN layer decreases.

[0107] Compared to SLG / h-BN / n-GaN heterojunctions with larger depletion region areas, SLG / h-BN / p-GaN heterojunctions with smaller depletion region areas exhibit stronger built-in electric field strength. With increasing h-BN thickness, the Fermi level of SLG on both n-GaN and p-GaN substrates gradually approaches the Dirac point, while the contact potential difference of the SLG / h-BN / n-GaN junction gradually increases, and that of the SLG / h-BN / p-GaN junction gradually decreases. Calculations show that the surface properties of the semiconductor have a significant impact on the charge transport and interface physics of the heterojunction. The proposed "intercalation doping" strategy provides a fundamental framework for the tailoring of van der Waals heterojunctions, promoting the understanding and design of two-dimensional / three-dimensional heterojunction interfaces for next-generation devices.

[0108] Example 3

[0109] This embodiment illustrates the ultraviolet photoelectric response test of the above-described p-type device structure, as shown below.

[0110] For SLG / h-BN / p-GaN devices with an intercalation number of 2, the response characteristics of the devices were tested under 365nm ultraviolet light source irradiation:

[0111] The responsiveness reaches 0.35 A / W;

[0112] The detection rate is 1.2 × 10⁻⁶. 12 Jones;

[0113] Response time less than 100ns;

[0114] It remains stable in high-temperature environments (above 150℃).

[0115] In summary, the embodiments of the present invention provide a high-performance ultraviolet photodetector based on a graphene / h-BN / p-GaN heterojunction. By synergistically controlling the number of h-BN layers and the p-type GaN substrate, precise control of the interface physical properties is achieved, significantly improving the ultraviolet detection performance of the device. This device has advantages such as low dark current, fast response speed, and good environmental stability, and is suitable for ultraviolet detection applications in harsh environments such as high temperature and high radiation.

[0116] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A heterojunction semiconductor structure, characterized in that, It includes a p-type GaN, an interface insertion layer, and a graphene layer in sequential contact. The interface insertion layer is composed of h-BN layers, and the number of h-BN layers in the interface insertion layer is 1-5.

2. The heterojunction semiconductor structure according to claim 1, characterized in that, The number of h-BN layers in the interface insertion layer makes the Fermi level of the graphene layer approach the Dirac point.

3. The heterojunction semiconductor structure according to claim 2, characterized in that, The number of h-BN layers in the interface insertion layer is selected as 1-3.

4. The heterojunction semiconductor structure according to claim 1, characterized in that, The graphene layer is selected from monolayer graphene.

5. The method for preparing the heterojunction semiconductor structure according to any one of claims 1-4, characterized in that, include: Provides p-type GaN substrates; The h-BN layer is supported by a first polymer film, and the h-BN layer is attached to the p-type GaN substrate. Remove the first polymer film to obtain a p-type GaN / h-BN composite, and optionally repeat several h-BN layers. A second polymer film is used to support a graphene layer, which is then attached to the h-BN layer of the p-type GaN / h-BN assembly. The second polymer film is removed to obtain a heterojunction semiconductor structure.

6. The preparation method according to claim 5, characterized in that, Specifically, it includes: The h-BN layer is grown using a first metal substrate; The first polymer film is formed by coating the surface of the h-BN layer; The first metal substrate is removed by etching to obtain a combination of the first polymer film and the h-BN layer; And / or, the graphene layer is grown using a second metal substrate; The second polymer film is formed by coating the surface of the graphene layer; The second metal substrate is removed by etching to obtain the combination of the second polymer film and the graphene layer.

7. The preparation method according to claim 5, characterized in that, The method for removing the first polymer film or the second polymer film specifically includes: The first or second polymer film is removed by dissolving it with an organic solvent; The residual adhesive in the first or second polymer film is then removed by annealing.

8. A photoelectric sensing device, characterized in that, Includes the heterojunction semiconductor structure, the first electrode, and the second electrode as described in any one of claims 1-4; The first electrode is in contact with the p-type GaN in the heterojunction semiconductor structure, and the second electrode is in contact with the graphene layer in the heterojunction semiconductor structure.

9. The application of the photoelectric sensing device according to claim 8 in ultraviolet light detection, flame sensing, ultraviolet communication or biochemical detection.

10. The application according to claim 9, characterized in that, The operating temperature of the photoelectric sensor is above 150°C.

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