High-gain 4H-SiC ultraviolet position sensitive detector and preparation method thereof

Abstract

The invention provides a high-gain 4H-SiC ultraviolet position sensitive detector and a preparation method thereof, and relates to the technical field of semiconductor photoelectric detection. A high-gain 4H-SiC ultraviolet position sensitive detector is realized through a first n-type 4H-SiC layer, a p-type 4H-SiC layer and a second n-type 4H-SiC layer, namely, an n +-p-n-structure, and a wide bandgap semiconductor material 4H-SiC is used as a device main body for migration of carriers irradiated by light. The material has the outstanding characteristics of large forbidden band width, high critical displacement energy, high thermal conductivity coefficient, good chemical stability and the like. According to the device structure, by introducing an internal gain mechanism, the photoelectric conversion efficiency and the position resolution ratio under the weak light condition are remarkably improved, and the limitations that an existing silicon-based PSD is large in background noise, and performance attenuation or damage is prone to occurring under the extreme environments of high temperature, intense radiation and the like are effectively overcome.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor photoelectric detection, and particularly relates to a high-gain 4H-SiC ultraviolet position sensitive detector and a preparation method thereof. BACKGROUND

[0002] As a kind of semiconductor device based on lateral photoelectric effect, a position sensitive detector (PSD for short) realizes rapid positioning by detecting the energy center position of a light spot on a photosensitive surface, and has the advantages of simple circuit and fast response speed. At present, commercial PSDs mainly adopt silicon materials, and their structures include one-dimensional linear and two-dimensional surface array types, wherein the two-dimensional PSD can realize planar position detection through four-electrode, pillow-shaped electrode or double-sided electrode layout. However, the existing silicon-based PSDs have the problems of poor spectral selectivity, weak anti-radiation capability and insufficient high-temperature stability. For example, since the band gap of silicon is relatively narrow (about 1.1 eV), the spectral response range covers visible light to near-infrared waveband, so that the device needs to rely on an external filtering system to suppress background interference when detecting in the ultraviolet waveband (200 nm-280 nm), which significantly increases the system complexity; in addition, the high-temperature resistance and anti-radiation performance of silicon material are poor, and the performance is prone to degradation under the condition of more than 150 DEG C or strong radiation environment, which is difficult to meet the needs of extreme working conditions such as aerospace and nuclear industry.

[0003] Wide-bandgap semiconductor material 4H-SiC has the characteristics of large band gap, high critical displacement energy, high thermal conductivity and good chemical stability, and has significant material performance advantages in the preparation of position sensitive detector devices working in the ultraviolet waveband. However, the existing ultraviolet position sensitive detectors based on 4H-SiC mostly adopt conventional PN diode structures, and their detection capability under weak light condition is limited, and the signal-to-noise ratio is low, which makes it difficult to meet the high-precision application requirements of position resolution and detection accuracy. SUMMARY

[0004] In view of the above problems, the application provides a high-gain 4H-SiC ultraviolet position sensitive detector and a preparation method thereof, which significantly improves the weak light signal response and spatial resolution capability by introducing an internal gain mechanism, and optimizes the device structure and preparation process to realize high-precision, extreme environment-resistant solar blind ultraviolet position sensitive detection. The specific scheme is as follows:

[0005] The first aspect of the application provides a high-gain 4H-SiC ultraviolet position sensitive detector, which comprises:

[0006] a 4H-SiC substrate;

[0007] a first n-type 4H-SiC layer, a p-type 4H-SiC layer and a second n-type 4H-SiC layer are sequentially stacked on one side of the 4H-SiC substrate; the doping concentration of the first n-type 4H-SiC layer is less than that of the second n-type 4H-SiC layer; the second n-type 4H-SiC layer has first to fourth electrode regions on the side away from the 4H-SiC substrate; the first electrode region and the second electrode region are oppositely arranged in a first direction, and the third electrode region and the fourth electrode region are oppositely arranged in a second direction, wherein the first direction and the second direction are perpendicular to each other;

[0008] a first ohmic contact electrode on the first electrode region, a second ohmic contact electrode on the second electrode region, a third ohmic contact electrode on the third electrode region, and a fourth ohmic contact electrode on the fourth electrode region;

[0009] a common electrode electrically connected to the first n-type 4H-SiC layer.

[0010] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the 4H-SiC substrate is an n-type 4H-SiC conductive substrate.

[0011] The common electrode is located on the side of the n-type 4H-SiC conductive substrate away from the first n-type 4H-SiC layer.

[0012] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the 4H-SiC substrate is a 4H-SiC semi-insulating substrate.

[0013] The high-gain 4H-SiC ultraviolet position sensitive detector further comprises:

[0014] an n-type 4H-SiC buffer layer between the 4H-SiC semi-insulating substrate and the first n-type 4H-SiC layer;

[0015] the first n-type 4H-SiC layer, the p-type 4H-SiC layer and the second n-type 4H-SiC layer expose part of the surface of the n-type 4H-SiC buffer layer;

[0016] The common electrode is located on the surface exposed by the n-type 4H-SiC buffer layer.

[0017] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the doping concentration of the first n-type 4H-SiC layer ranges from 1×10 14 cm -3 to 1×10 16 cm -3 .

[0018] The doping concentration of the p-type 4H-SiC layer ranges from 1 x 10 16 cm -3 to 1 x 10 18 cm -3 .

[0019] The doping concentration of the second n-type 4H-SiC layer ranges from 1 x 10 17 cm -3 to 2 x 10 19 cm -3 .

[0020] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the doping concentration of the first n-type 4H-SiC layer ranges from 1 μm to 10 μm;

[0021] The doping concentration of the p-type 4H-SiC layer ranges from 0.1 μm to 2 μm;

[0022] The doping concentration of the second n-type 4H-SiC layer ranges from 0.1 μm to 2 μm;

[0023] The thickness of the first ohmic contact electrode is greater than 0.1 μm;

[0024] The thickness of the second ohmic contact electrode is greater than 0.1 μm;

[0025] The thickness of the third ohmic contact electrode is greater than 0.1 μm;

[0026] The thickness of the fourth ohmic contact electrode is greater than 0.1 μm.

[0027] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the shapes of the first ohmic contact electrode, the second ohmic contact electrode, the third ohmic contact electrode and the fourth ohmic contact electrode are long strips;

[0028] The length extension directions of the first ohmic contact electrode and the second ohmic contact electrode are perpendicular to the first direction;

[0029] The length extension directions of the third ohmic contact electrode and the fourth ohmic contact electrode are perpendicular to the second direction;

[0030] The first ohmic contact electrode, the second ohmic contact electrode, the third ohmic contact electrode and the fourth ohmic contact electrode jointly enclose a square-shaped photosensitive region.

[0031] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the high-gain 4H-SiC ultraviolet position sensitive detector further comprises:

[0032] a first metal conductive electrode located on a side of the first ohmic contact electrode away from the 4H-SiC substrate, a second metal conductive electrode located on a side of the second ohmic contact electrode away from the 4H-SiC substrate, a third metal conductive electrode located on a side of the third ohmic contact electrode away from the 4H-SiC substrate, and a fourth metal conductive electrode located on a side of the fourth ohmic contact electrode away from the 4H-SiC substrate.

[0033] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the high-gain 4H-SiC ultraviolet position sensitive detector further comprises:

[0034] a passivation layer located on a side of the second n-type 4H-SiC layer away from the 4H-SiC substrate;

[0035] the passivation layer has a groove region, and the groove region exposes the first to fourth electrode regions;

[0036] the first ohmic contact electrode contacts the first electrode region through a corresponding groove region, the second ohmic contact electrode contacts the second electrode region through a corresponding groove region, the third ohmic contact electrode contacts the third electrode region through a corresponding groove region, and the fourth ohmic contact electrode contacts the fourth electrode region through a corresponding groove region.

[0037] Preferably, in the high-gain 4H-SiC ultraviolet position sensitive detector, the thickness of the passivation layer is less than 200 nm.

[0038] The second aspect of the present application provides a preparation method of a high-gain 4H-SiC ultraviolet position sensitive detector, and the preparation method comprises:

[0039] providing a 4H-SiC substrate;

[0040] forming a first n-type 4H-SiC layer, a p-type 4H-SiC layer, and a second n-type 4H-SiC layer which are sequentially stacked on one side of the 4H-SiC substrate; wherein the doping concentration of the first n-type 4H-SiC layer is less than the doping concentration of the second n-type 4H-SiC layer; the side of the second n-type 4H-SiC layer away from the 4H-SiC substrate has first to fourth electrode regions; the first electrode region and the second electrode region are oppositely arranged in a first direction, the third electrode region and the fourth electrode region are oppositely arranged in a second direction, and the first direction and the second direction are perpendicular;

[0041] forming a first ohmic contact electrode on the first electrode region, forming a second ohmic contact electrode on the second electrode region, forming a third ohmic contact electrode on the third electrode region, and forming a fourth ohmic contact electrode on the fourth electrode region;

[0042] forming a common electrode electrically connected with the first n-type 4H-SiC layer.

[0043] By the above technical solution, the application provides a high-gain 4H-SiC ultraviolet position sensitive detector and a preparation method thereof, which uses a wide-bandgap semiconductor material 4H-SiC as a device main body to provide migration of carriers after light irradiation, and has the outstanding characteristics of large bandgap, high critical displacement energy, high thermal conductivity coefficient, and good chemical stability. The device structure introduces an internal gain mechanism, significantly improves the photoelectric conversion efficiency and position resolution under weak light conditions, and effectively overcomes the limitations of large background noise of existing silicon-based PSDs and easy performance degradation or damage in extreme environments such as high temperature and strong radiation.

[0044] The high-gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment of the application is amplified through a phototransistor gain mechanism. The phototransistor is different from the bipolar transistor in that the base is suspended, i.e., there is no base electrode. The current of the high-gain 4H-SiC ultraviolet position sensitive detector can be directly controlled by external light, and the device working principle is as follows: the first n-type 4H-SiC layer (which can be understood as a low-doped n-type 4H-SiC layer), the p-type 4H-SiC layer, and the second n-type 4H-SiC layer (which can be understood as a high-doped n-type 4H-SiC layer) functionally serve as a collector region, a base region, and an emitter region, respectively; a bias voltage is applied between the emitter (the first, second, third, and fourth ohmic contact electrodes) and the collector (the common electrode), so that the emitter junction is forward biased and the collector junction is reverse biased. When the high-gain 4H-SiC ultraviolet position sensitive detector detects light, the light will be absorbed by the collector junction and generate electron-hole pairs. The photo-generated holes will move to the base region under the action of the electric field. Due to the existence of the potential barrier between the emitter region and the base region, the holes will gather in the base region, thereby reducing the potential barrier height of the emitter junction. If the lifetime of the injected electrons in the base region is greater than the transport time of the electrons through the base, the incident light current can be amplified through the transistor mechanism. The first, second, third, and fourth ohmic contact electrodes located above the second n-type 4H-SiC layer will output a current proportional to the distance from the center of the light spot to the respective electrode, thereby effectively detecting the position of the center of the incident light spot. BRIEF DESCRIPTION OF DRAWINGS

[0045] The above and other features, advantages, and aspects of embodiments of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The same or similar components have the same or similar reference labels. It should be understood that the drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the principles of the embodiments.

[0046] Figure 1 A perspective structural schematic diagram of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application;

[0047] Figure 2 A perspective structural schematic diagram of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application; Figure 1 A top structural schematic diagram of the structure shown in FIG. 1;

[0048] Figure 3 A perspective structural schematic diagram of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application;

[0049] Figure 4 A perspective structural schematic diagram of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application; Figure 3 A top structural schematic diagram of the structure shown in FIG. 1;

[0050] Figure 5 A perspective structural schematic diagram of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application; Figure 1 An electric field distribution schematic diagram of the device structure shown in FIG. 1 obtained by Silvaco software simulation;

[0051] Figure 6 An electric field distribution schematic diagram of the device structure shown in FIG. 1 obtained by Silvaco software simulation; Figure 1 Characteristics curves of dark current and photocurrent varying with voltage under experimental test and simulation simulation conditions of the device structure shown in FIG. 1;

[0052] Figure 7 A flow schematic diagram of a preparation method of a high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application. DETAILED DESCRIPTION

[0053] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application. The terms used in the embodiment part of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. Those skilled in the art can know that, with the development of technology and the appearance of new scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0054] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0055] It should be noted that the orientation words appearing in the present application are based on the relative position relationship shown in the drawings and cannot be used as absolute limitations on the present application.

[0056] Reference Figure 1 , Figure 1 A high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application is shown in the perspective structural schematic diagram; reference Figure 2 , Figure 2 A high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application is shown in the perspective structural schematic diagram; reference Figure 1 , Figure 3 , Figure 3 A high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application is shown in the perspective structural schematic diagram; reference Figure 4 , Figure 4 A high-gain 4H-SiC ultraviolet position-sensitive detector provided by an embodiment of the present application is shown in the perspective structural schematic diagram; reference Figure 3 The high-gain 4H-SiC ultraviolet position-sensitive detector provided by the embodiment of the present application comprises a 4H-SiC substrate 1.

[0057] A first n-type 4H-SiC layer 2, a p-type 4H-SiC layer 3 and a second n-type 4H-SiC layer 4 are sequentially stacked on one side of the 4H-SiC substrate 1; wherein the doping concentration of the first n-type 4H-SiC layer 2 is less than the doping concentration of the second n-type 4H-SiC layer 4; the second n-type 4H-SiC layer 4 has first to fourth electrode areas on the side away from the 4H-SiC substrate 1; the first electrode area and the second electrode area are oppositely arranged in a first direction, the third electrode area and the fourth electrode area are oppositely arranged in a second direction, and the first direction and the second direction are perpendicular.

[0058] A first ohmic contact electrode 5 on the first electrode area, a second ohmic contact electrode 6 on the second electrode area, a third ohmic contact electrode 7 on the third electrode area, and a fourth ohmic contact electrode 8 on the fourth electrode area.

[0059] A common electrode 9 electrically connected to the first n-type 4H-SiC layer 2.

[0060] Specifically, in the embodiment of the present application, the first electrode area, the second electrode area, the third electrode area and the fourth electrode area are distributed on the outer edge area of the second n-type 4H-SiC layer 4; the doping concentration of the first n-type 4H-SiC layer 2 is less than the doping concentration of the second n-type 4H-SiC layer 4, in other words, the first n-type 4H-SiC layer 2 can be understood as a low-doped n-type 4H-SiC layer, and the second n-type 4H-SiC layer 4 can be understood as a high-doped n-type 4H-SiC layer.

[0061] The embodiment of the present application provides two high-gain 4H-SiC ultraviolet position sensitive detectors with different structures. Figure 1 and Figure 2 The embodiment of the present application provides two high-gain 4H-SiC ultraviolet position sensitive detectors with different structures.

[0062] As shown in Figure 1 and Figure 2 , the high-gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment of the present application is characterized in that the 4H-SiC substrate 1 is an n-type 4H-SiC conductive substrate 11; and the common electrode 9 is located on the side of the n-type 4H-SiC conductive substrate 11 away from the first n-type 4H-SiC layer 2. Optionally, the common electrode 9 covers the entire surface of the n-type 4H-SiC conductive substrate 11.

[0063] Optionally, the material of the common electrode 9 is one of nickel, titanium, aluminum, gold and the like or a mixture of two or more of the materials in any ratio.

[0064] The doping concentration of the first n-type 4H-SiC layer 2 ranges from 1×10 14 cm -3 to 1×10 16 cm -3 .

[0065] The doping concentration of the p-type 4H-SiC layer 3 ranges from 1×10 16 cm -3 to 1×10 18 cm -3 .

[0066] The doping concentration of the second n-type 4H-SiC layer 4 ranges from 1×10 17 cm -3 to 2×10 19 cm -3 .

[0067] The doping concentration of the first n-type 4H-SiC layer 2 ranges from 1 μm to 10 μm.

[0068] The doping concentration of the p-type 4H-SiC layer 3 ranges from 0.1 μm to 2 μm.

[0069] The doping concentration of the second n-type 4H-SiC layer 4 ranges from 0.1 μm to 2 μm.

[0070] The thickness of the first ohmic contact electrode 5 is greater than 0.1 μm.

[0071] The thickness of the second ohmic contact electrode 6 is greater than 0.1 μm.

[0072] The thickness of the third ohmic contact electrode 7 is greater than 0.1 μm.

[0073] The thickness of the fourth ohmic contact electrode 8 is greater than 0.1 μm.

[0074] The material of the first ohmic contact electrode 5 is one or more than two of nickel, titanium, aluminum, gold and the like in any proportion.

[0075] The material of the second ohmic contact electrode 6 is one or more than two of nickel, titanium, aluminum, gold and the like in any proportion.

[0076] The material of the third ohmic contact electrode 7 is one or more than two of nickel, titanium, aluminum, gold and the like in any proportion.

[0077] The material of the fourth ohmic contact electrode 8 is one or more than two of nickel, titanium, aluminum, gold and the like in any proportion.

[0078] The first ohmic contact electrode 5, the second ohmic contact electrode 6, the third ohmic contact electrode 7 and the fourth ohmic contact electrode 8 are in the shape of a long strip.

[0079] The length extension direction of the first ohmic contact electrode 5 and the second ohmic contact electrode 6 is perpendicular to the first direction.

[0080] The length extension direction of the third ohmic contact electrode 7 and the fourth ohmic contact electrode 8 is perpendicular to the second direction.

[0081] The first ohmic contact electrode 5, the second ohmic contact electrode 6, the third ohmic contact electrode 7 and the fourth ohmic contact electrode 8 jointly form a square-shaped photosensitive region.

[0082] It can be understood that the inner sides of the first ohmic contact electrode 5, the second ohmic contact electrode 6, the third ohmic contact electrode 7 and the fourth ohmic contact electrode 8 jointly form a square-shaped photosensitive region, which can also be referred to as a photosensitive region. In the embodiment of the present application, a square-shaped photosensitive region is taken as an example for illustration, and the photosensitive area thereof includes but is not limited to 8 mm x 8 mm.

[0083] The high-gain 4H-SiC ultraviolet position-sensitive detector further comprises:

[0084] A first metal conductive electrode 10 located on the side of the first ohmic contact electrode 5 away from the 4H-SiC substrate 1, a second metal conductive electrode 11 located on the side of the second ohmic contact electrode 6 away from the 4H-SiC substrate 1, a third metal conductive electrode 12 located on the side of the third ohmic contact electrode 7 away from the 4H-SiC substrate 1, and a fourth metal conductive electrode 13 located on the side of the fourth ohmic contact electrode 8 away from the 4H-SiC substrate 1; wherein the first metal conductive electrode 10 includes but is not limited to a titanium layer and a gold layer, the second metal conductive electrode 11 includes but is not limited to a titanium layer and a gold layer, the third metal conductive electrode 12 includes but is not limited to a titanium layer and a gold layer, and the fourth metal conductive electrode 14 includes but is not limited to a titanium layer and a gold layer, the first metal conductive electrode 10 is completely located on the first ohmic contact electrode 5, the second metal conductive electrode 11 is completely located on the second ohmic contact electrode 6, the third metal conductive electrode 12 is completely located on the third ohmic contact electrode 7, and the fourth metal conductive electrode 13 is completely located on the fourth ohmic contact electrode 8.

[0085] The arrangement of the metal conductive electrode can effectively improve the current spreading and carrier collection capability of the device, and is used for wire packaging.

[0086] The high-gain 4H-SiC ultraviolet position sensitive detector further comprises a passivation layer 14 located on the side of the second n-type 4H-SiC layer 4 away from the 4H-SiC substrate 1.

[0087] The passivation layer 14 has a groove region, and the groove region exposes the first to fourth electrode regions.

[0088] The first ohmic contact electrode 5 is in contact with the first electrode region through a corresponding groove region, the second ohmic contact electrode 6 is in contact with the second electrode region through a corresponding groove region, the third ohmic contact electrode 7 is in contact with the third electrode region through a corresponding groove region, and the fourth ohmic contact electrode 8 is in contact with the fourth electrode region through a corresponding groove region.

[0089] Optionally, the thickness of the passivation layer 14 is less than 200 nm, and is preferably 30 nm.

[0090] The groove region can include a first groove region, a second groove region, a third groove region and a fourth groove region, the first groove region exposes the first electrode region, the second groove region exposes the second electrode region, the third groove region exposes the third electrode region, and the fourth groove region exposes the fourth electrode region, the first ohmic contact electrode 5 contacts the first electrode region through the first groove region, the second ohmic contact electrode 6 contacts the second electrode region through the second groove region, the third ohmic contact electrode 7 contacts the third electrode region through the third groove region, and the fourth ohmic contact electrode 8 contacts the fourth electrode region through the fourth groove region.

[0091] Based on Figure 1 and Figure 2 the high-gain 4H-SiC ultraviolet position-sensitive detector shown, when the device is irradiated by ultraviolet light, photo-generated electrons and photo-generated holes with opposite migration directions can be generated in the collector junction of the first n-type 4H-SiC layer 2 and the p-type 4H-SiC layer 3, the photo-generated holes induce a potential barrier reduction in the base region of the p-type 4H-SiC layer 3, a transistor gain is generated, and amplification of the incident light signal is realized. The first, second, third and fourth metal conductive electrodes above the first, second, third and fourth ohmic contact electrodes above the second n-type 4H-SiC layer 4 output currents proportional to the distance from the center of the light spot to the respective electrodes, thereby realizing effective detection of the position of the center of the incident light spot.

[0092] If the geometric center of the high-gain 4H-SiC ultraviolet position-sensitive detector is taken as the origin, the position of the incident light spot can be determined by reading the currents of the first, second, third and fourth ohmic contact electrodes 、 、 and The coordinates of the center of the incident light spot on the high-gain 4H-SiC ultraviolet position-sensitive detector are represented as:

[0093]

[0094] wherein, and are linear constants; is related to the side length of the photosensitive region at the positions of the first ohmic contact electrode 5 and the second ohmic contact electrode 6, is related to the side length of the photosensitive region at the positions of the third ohmic contact electrode 7 and the fourth ohmic contact electrode 8; when the photosensitive region is a square, there is a relationship of

[0095] The following are examples of Figure 3 and Figure 4 ​​The structure shown is described.

[0096] As shown in Figure 3 and Figure 4 The high-gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment of the present application has a 4H-SiC substrate 1 which is a 4H-SiC semi-insulating substrate 12.

[0097] The high-gain 4H-SiC ultraviolet position sensitive detector further comprises an n-type 4H-SiC buffer layer 15 between the 4H-SiC semi-insulating substrate 12 and the first n-type 4H-SiC layer 2.

[0098] The first n-type 4H-SiC layer 2, the p-type 4H-SiC layer 3 and the second n-type 4H-SiC layer 4 expose part of the surface of the n-type 4H-SiC buffer layer 15.

[0099] The common electrode 9 is on the surface of the n-type 4H-SiC buffer layer 15.

[0100] In the embodiment of the present application, the n-type 4H-SiC buffer layer 15 can be a highly doped n-type 4H-SiC buffer layer, and the device structure is a quasi-vertical device structure.

[0101] At this time, the first n-type 4H-SiC layer 2, the p-type 4H-SiC layer 3 and the second n-type 4H-SiC layer 4 expose part of the surface of the n-type 4H-SiC buffer layer 15, and the common electrode 9 is on the surface of the n-type 4H-SiC buffer layer 15, thereby forming another structure of high-gain 4H-SiC ultraviolet position sensitive detector.

[0102] Optionally, the thickness of the n-type 4H-SiC buffer layer 15 is 0.5-5 μm, preferably 2 μm; the doping concentration of the n-type 4H-SiC buffer layer 15 is greater than 1×10 18 cm -3 , preferably 1×10 19 cm -3 .

[0103] It should be noted that, based on Figure 3The high-gain 4H-SiC ultraviolet position sensitive detector shown in the structure further comprises a fourth metal conductive electrode 16 located on the side of the common electrode 9 away from the 4H-SiC semi-insulating substrate 12.

[0104] It should be noted that the content here only reflects the differences between the two structures, and the same parts will not be described here, and the above-mentioned content about the structure shown in the structure can be referred to. Figure 1 and Figure 3 The differences between the two structures are not described here, and the same parts will not be described here, and the above-mentioned content about the structure shown in the structure can be referred to. Figure 1

[0105] As described above, the embodiment of the application realizes a high-gain 4H-SiC ultraviolet position sensitive detector by the first n-type 4H-SiC layer 2, the p-type 4H-SiC layer 3 and the second n-type 4H-SiC layer 4 (i.e. n + -p-n - ) structure. Figure 5 , Figure 5 The device structure shown in the embodiment of the application provides a NPN type 4H-SiC position sensitive detector based on Figure 1 The electric field distribution schematic diagram obtained by simulating the device structure shown in the embodiment of the application by Silvaco software clearly shows the electric field distribution diagram of the NPN type 4H-SiC position sensitive detector under the action of bias voltage; refer to Figure 6 , Figure 6 The device structure shown in the embodiment of the application provides a NPN type 4H-SiC position sensitive detector based on Figure 1 The dark current and photocurrent-voltage characteristic curves under experimental test and simulation conditions of the device structure shown in the embodiment of the application, wherein curve 1 represents the simulated photocurrent curve, curve 2 represents the experimental photocurrent curve, curve 3 represents the simulated dark current curve, and curve 4 represents the experimental dark current curve. The NPN type gain structure forms a reverse-biased collector junction and a forward-biased emitter junction through the intermediate p-type 4H-SiC layer 3 and the first n-type 4H-SiC layer 2 and the second n-type 4H-SiC layer 4 on both sides. After the incident ultraviolet photons excite electron-hole pairs in the collector junction depletion region, the holes gather in the base region under the electric field, inducing the reduction of the junction barrier, thereby realizing the internal gain of the photocurrent. This mechanism enables the position sensitive detector to have high gain characteristics in the ultraviolet band, significantly improving the detection sensitivity. It can be predicted that as the bias voltage increases, the internal gain effect of the device will be more significant, and the quantum efficiency will be further improved.

[0106] ​Compared with the problems of low gain and large influence of material defects and interface state on responsivity of a traditional PIN type ultraviolet position sensitive detector, the high gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment has the characteristics of high gain, good linearity and uniform response. The full epitaxial structure avoids the lattice damage caused by ion implantation, is beneficial to maintaining high carrier lifetime and high mobility of the material, and thus guarantees the stability of the gain process. In addition, the high thermal conductivity and strong anti-radiation characteristics of the 4H-SiC material itself, combined with the advantage of good planar process compatibility, make the detector suitable for ultraviolet position detection applications in harsh environments such as high temperature and strong radiation, and have good industrialization prospects.

[0107] In general, the high gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment uses a wide bandgap semiconductor material 4H-SiC as a device main body for the migration of carriers after receiving light irradiation, has the outstanding characteristics of large bandgap, high critical displacement energy, high thermal conductivity coefficient and good chemical stability. The device structure significantly improves the photoelectric conversion efficiency and position resolution under weak light conditions by introducing an internal gain mechanism, and effectively overcomes the limitations of large background noise of existing silicon-based PSDs and easy performance degradation or damage in extreme environments such as high temperature and strong radiation.

[0108] The high gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment realizes amplification through a phototransistor gain mechanism. The phototransistor is different from the bipolar transistor in that the base is suspended, i.e., there is no base electrode. The current of the high gain 4H-SiC ultraviolet position sensitive detector can be directly controlled by external light, and the device working principle is as follows: the first n-type 4H-SiC layer 2 (which can be understood as a low-doped n-type 4H-SiC layer), the p-type 4H-SiC layer 3 and the second n-type 4H-SiC layer 4 (which can be understood as a high-doped n-type 4H-SiC layer) functionally serve as the collector region, the base region and the emitter region respectively; a bias voltage is applied between the emitter (the first, second, third and fourth ohmic contact electrodes) and the collector (the common electrode 9), so that the emission junction is forward biased and the collector junction is reverse biased. When the high gain 4H-SiC ultraviolet position sensitive detector detects light, the light will be absorbed by the collector junction and generate electron-hole pairs. The photo-generated holes will move to the base region under the action of the electric field. Due to the existence of the potential barrier between the emitter region and the base region, the holes will gather in the base region, thereby reducing the potential barrier height of the emission junction. If the lifetime of the injected electrons in the base region is greater than the transport time of the electrons through the base, the incident light current can be amplified through the transistor mechanism. The first, second, third and fourth ohmic contact electrodes located above the second n-type 4H-SiC layer 4 will output a current proportional to the distance from the center of the light spot to the respective electrode, thereby effectively detecting the position of the center of the incident light spot.

[0109] The high-gain 4H-SiC ultraviolet position sensitive detector can be applied to motion tracking, vibration monitoring, space optical communication and other scenes requiring high-precision ultraviolet spot positioning.

[0110] Based on the above-mentioned embodiments of the present application, in another embodiment of the present application, a preparation method of a high-gain 4H-SiC ultraviolet position sensitive detector is also provided, referring to Figure 7 , Figure 7 A flowchart of the preparation method of the high-gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment of the present application is shown. The preparation method of the high-gain 4H-SiC ultraviolet position sensitive detector provided by the embodiment of the present application comprises:

[0111] S101: providing a 4H-SiC substrate 1.

[0112] S102: forming a first n-type 4H-SiC layer 2, a p-type 4H-SiC layer 3 and a second n-type 4H-SiC layer 4 which are sequentially stacked on one side of the 4H-SiC substrate 1; wherein the doping concentration of the first n-type 4H-SiC layer 2 is less than the doping concentration of the second n-type 4H-SiC layer 4; the second n-type 4H-SiC layer 4 has first to fourth electrode areas on the side away from the 4H-SiC substrate 1; the first electrode area and the second electrode area are oppositely arranged in a first direction, the third electrode area and the fourth electrode area are oppositely arranged in a second direction, and the first direction and the second direction are perpendicular.

[0113] S103: forming a first ohmic contact electrode 5 on the first electrode area, a second ohmic contact electrode 6 on the second electrode area, a third ohmic contact electrode 7 on the third electrode area, and a fourth ohmic contact electrode 8 on the fourth electrode area.

[0114] S104: forming a common electrode 9 electrically connected to the first n-type 4H-SiC layer 2.

[0115] The following will be described by taking the preparation flow of the device structure shown in Figure 1 as an example.

[0116] The n-type 4H-SiC conductive substrate 11 is taken as an epitaxial wafer, and the first n-type 4H-SiC layer 2, the p-type 4H-SiC layer 3 and the second n-type 4H-SiC layer 4 are sequentially grown thereon. For example, the first n-type 4H-SiC layer 2 is an n-type doped silicon carbide layer with a thickness of 3 μm and a doping concentration of 1×10 16 cm -3 ; the p-type 4H-SiC layer 3 is a p-type doped silicon carbide layer with a thickness of 0.4 μm and a doping concentration of 1×10 17 cm -3; the second n-type 4H-SiC layer 4 is an n-type doped silicon carbide layer with a thickness of 0.2 μm and a doping concentration of 1 x 1018cm 19 cm -3 .

[0117] A passivation layer 14 is formed on the side surface of the second n-type 4H-SiC layer 4 away from the n-type 4H-SiC conductive substrate 11 by high-temperature thermal oxidation. The material of the passivation layer 14 includes, but is not limited to, SiO2material. For example, on the top of the device, i.e., on the side surface of the second n-type 4H-SiC layer 4 away from the n-type 4H-SiC conductive substrate 11, a passivation layer 14 of SiO2with a thickness of 30 nm is formed on the surface of the wafer by using the method of "dry-oxygen-wet-oxygen-dry-oxygen" alternating high-temperature thermal oxidation.

[0118] The photoetching-wet etching-peeling process is combined on the top of the passivation layer 14, and the first, second, third and fourth ohmic contact electrodes are deposited in the selected area. For example, a layer of photoresist is uniformly spin-coated above the passivation layer 14, and after exposure, development and post-baking, a wet etching photoresist mask is formed to define the first to fourth electrode areas in the photosensitive region, and then the passivation layer 14 in the area of the ohmic contact window is removed by wet etching to form a corresponding recessed area, exposing the corresponding area of the second n-type 4H-SiC layer 4, for example, the buffered oxide etching (English full name: Buffered Oxide Etch, abbreviated as BOE) method etches down the passivation layer 14 until the top of the second n-type 4H-SiC layer 4.

[0119] Then, the first, second, third and fourth ohmic contact electrodes are deposited on the exposed second n-type 4H-SiC layer 4 in the ohmic contact window by using the PVD (English full name: Physical Vapor Deposition) method. For example, the second n-type 4H-SiC layer 4 in the four ohmic contact windows is coated with a Ni / Ti / Al / Au multilayer electrode by using the electron beam evaporation method, forming the first, second, third and fourth ohmic contact electrodes; the metal thickness of the Ni / Ti / Al / Au multilayer electrode is 35 nm / 50 nm / 100 nm / 100 nm in turn. The first, second, third and fourth ohmic contact electrodes finally surround the square photosensitive area of the position sensitive detector in the embodiment of the application.

[0120] A common electrode 9 is deposited on the side surface of the n-type 4H-SiC conductive substrate 11 away from the first n-type 4H-SiC layer 2, and an ohmic contact is formed by rapid thermal annealing. For example, a Ni / Ti / Al / Au multi-layer electrode is deposited on the side surface of the n-type 4H-SiC conductive substrate 11 away from the first n-type 4H-SiC layer 2 by a PVD method using an electron beam evaporation process in a full-coverage manner to form the common electrode 9; the metal thickness of the Ni / Ti / Al / Au multi-layer electrode is 35 nm / 50 nm / 100 nm / 100 nm in sequence; and then a thermal annealing treatment is performed in a nitrogen atmosphere to form an ohmic contact. The temperature range of the rapid thermal annealing (RTA) is 800°C-850°C, and the processing time range is 2 min-3 min.

[0121] A metal conductive electrode is deposited above the first, second, third and fourth ohmic contact electrodes. For example, a metal conductive electrode region is formed by gluing, exposing, developing, and a Ti / Au double-layer electrode is deposited above the first, second, third and fourth ohmic contact electrodes by an electron beam evaporation method to form the metal conductive electrode, and the metal thickness of the Ti / Au double-layer electrode is 500 nm in sequence, thus completing the preparation of the device structure as shown in FIG. 1. Figure 1 The preparation of the device structure as shown in FIG. 1 is completed.

[0122] The preparation of the device structure as shown in FIG. 1 is completed. Figure 3 The preparation of the device structure as shown in FIG. 1 is completed.

[0123] A 4H-SiC semi-insulating substrate 12 is used as an epitaxial wafer, and an n-type 4H-SiC buffer layer 15, a first n-type 4H-SiC layer 2, a p-type 4H-SiC layer 3 and a second n-type 4H-SiC layer 4 are sequentially grown thereon.

[0124] The subsequent preparation process is the same as that of the device structure as shown in FIG. 1. Figure 1 Figure 1 Figure 3 Figure 1The preparation process of the shown device structure is similar, and the same parts are not described here. Before forming the passivation layer 14 by high-temperature thermal oxidation, a layer of photoresist is uniformly spin-coated on the top of the device, that is, on the side surface of the second n-type 4H-SiC layer 4 away from the 4H-SiC semi-insulating substrate 12. After exposure, development and post-baking, a dry etching thick photoresist mask is formed. Then, the inductively coupled plasma etching (ICP) method is used to etch downward to the top of the n-type 4H-SiC buffer layer 15, thereby forming a patterned region on the n-type 4H-SiC buffer layer 15. Only the second n-type 4H-SiC layer 4, the p-type 4H-SiC layer 3 and the first n-type 4H-SiC layer 2 in the patterned region are reserved, and a first step structure is formed with the n-type 4H-SiC buffer layer 15 below. The etching depth of the downward etching is 3.6 μm, and the photoresist is removed after the n-type 4H-SiC buffer layer 15 is exposed. It should be noted that the ICP etching mask in this step can also use the PVD method to form a metal mask.

[0125] Subsequently, the passivation layer 14 is formed by high-temperature thermal oxidation on the side surface of the second n-type 4H-SiC layer 4 away from the 4H-SiC semi-insulating substrate 12. Then, four ohmic electrode contact windows are formed by coating, exposing and developing. After etching away the passivation layer 14 corresponding to the ohmic electrode contact windows, the first, second, third and fourth ohmic contact electrodes are directly deposited, and the common electrode 9 is also formed at the same time. Then, the corresponding metal conductive electrodes are deposited on the first, second, third and fourth ohmic contact electrodes and the common electrode 9.

[0126] The high-gain 4H-SiC ultraviolet position-sensitive detector and the preparation method thereof provided by the present application are described in detail above. The principles and implementation manners of the present application are described by applying specific examples in this paper. The above examples are only used to help understand the method and core idea of the present application. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation manner and application range can be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

[0127] It should be noted that each embodiment in the specification focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0128] It is also noted that the relational terms herein, such as first and second, and the like, are used solely to distinguish one from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0129] The above description of disclosed embodiments provides enabling concepts for practicing or using the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high gain 4H-SiC ultraviolet position sensitive detector, characterized by, The high-gain 4H-SiC ultraviolet position sensitive detector comprises: a 4H-SiC substrate; a first n-type 4H-SiC layer, a p-type 4H-SiC layer and a second n-type 4H-SiC layer which are sequentially stacked on one side of the 4H-SiC substrate; wherein the doping concentration of the first n-type 4H-SiC layer is less than the doping concentration of the second n-type 4H-SiC layer; the second n-type 4H-SiC layer has first to fourth electrode areas on the side away from the 4H-SiC substrate; the first electrode area and the second electrode area are oppositely arranged in a first direction, the third electrode area and the fourth electrode area are oppositely arranged in a second direction, and the first direction and the second direction are perpendicular; a first ohmic contact electrode on the first electrode area, a second ohmic contact electrode on the second electrode area, a third ohmic contact electrode on the third electrode area, and a fourth ohmic contact electrode on the fourth electrode area; a common electrode electrically connected with the first n-type 4H-SiC layer.

2. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The 4H-SiC substrate is an n-type 4H-SiC conductive substrate; The common electrode is located on the side of the n-type 4H-SiC conductive substrate away from the first n-type 4H-SiC layer.

3. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The 4H-SiC substrate is a 4H-SiC semi-insulating substrate; The high-gain 4H-SiC ultraviolet position sensitive detector further comprises: an n-type 4H-SiC buffer layer between the 4H-SiC semi-insulating substrate and the first n-type 4H-SiC layer; the first n-type 4H-SiC layer, the p-type 4H-SiC layer and the second n-type 4H-SiC layer expose part of the surface of the n-type 4H-SiC buffer layer; the common electrode is located on the surface exposed by the n-type 4H-SiC buffer layer.

4. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The first n-type 4H-SiC layer has a doping concentration ranging from 1 x 1015 14 cm -3 to 1 x 1018 16 cm -3 -3 The p-type 4H-SiC layer has a doping concentration ranging from 1 x 1015 16 cm -3 to 1 x 1019 18 cm -3 -3 The second n-type 4H-SiC layer has a doping concentration ranging from 1 x 1018 17 cm -3 to 2 x 1018 19 cm -3 .

5. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The doping concentration of the first n-type 4H-SiC layer ranges from 1 μm to 10 μm; The doping concentration of the p-type 4H-SiC layer ranges from 0.1 μm to 2 μm; The doping concentration of the second n-type 4H-SiC layer ranges from 0.1 μm to 2 μm; The thickness of the first ohmic contact electrode is greater than 0.1 μm; The thickness of the second ohmic contact electrode is greater than 0.1 μm; The thickness of the third ohmic contact electrode is greater than 0.1 μm; The thickness of the fourth ohmic contact electrode is greater than 0.1 μm.

6. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The shapes of the first ohmic contact electrode, the second ohmic contact electrode, the third ohmic contact electrode and the fourth ohmic contact electrode are long strips; The length extension direction of the first ohmic contact electrode and the second ohmic contact electrode is perpendicular to the first direction; The length extension direction of the third ohmic contact electrode and the fourth ohmic contact electrode is perpendicular to the second direction; The first ohmic contact electrode, the second ohmic contact electrode, the third ohmic contact electrode and the fourth ohmic contact electrode together form a square-shaped photosensitive area.

7. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The high-gain 4H-SiC ultraviolet position sensitive detector further comprises: A first metal conductive electrode is located on the side of the first ohmic contact electrode away from the 4H-SiC substrate, a second metal conductive electrode is located on the side of the second ohmic contact electrode away from the 4H-SiC substrate, a third metal conductive electrode is located on the side of the third ohmic contact electrode away from the 4H-SiC substrate, and a fourth metal conductive electrode is located on the side of the fourth ohmic contact electrode away from the 4H-SiC substrate.

8. The high gain 4H-SiC ultraviolet position sensitive detector of claim 1, wherein, The high-gain 4H-SiC ultraviolet position sensitive detector further comprises: A passivation layer is located on the side of the second n-type 4H-SiC layer away from the 4H-SiC substrate. The passivation layer has a groove region that exposes the first to fourth electrode regions. The first ohmic contact electrode is in contact with the first electrode region through a corresponding groove region, the second ohmic contact electrode is in contact with the second electrode region through a corresponding groove region, the third ohmic contact electrode is in contact with the third electrode region through a corresponding groove region, and the fourth ohmic contact electrode is in contact with the fourth electrode region through a corresponding groove region.

9. The high gain 4H-SiC ultraviolet position sensitive detector of claim 8, wherein, The thickness of the passivation layer is less than 200 nm.

10. A method for fabricating a high-gain 4H-SiC ultraviolet position sensitive detector, characterized in that, The method for manufacturing the high-gain 4H-SiC ultraviolet position sensitive detector comprises: Providing a 4H-SiC substrate; On one side of the 4H-SiC substrate, a first n-type 4H-SiC layer, a p-type 4H-SiC layer, and a second n-type 4H-SiC layer are sequentially stacked; the doping concentration of the first n-type 4H-SiC layer is less than the doping concentration of the second n-type 4H-SiC layer; the side of the second n-type 4H-SiC layer away from the 4H-SiC substrate has first to fourth electrode regions; the first electrode region and the second electrode region are oppositely arranged in a first direction, the third electrode region and the fourth electrode region are oppositely arranged in a second direction, and the first direction and the second direction are perpendicular; A first ohmic contact electrode is formed on the first electrode region, a second ohmic contact electrode is formed on the second electrode region, a third ohmic contact electrode is formed on the third electrode region, and a fourth ohmic contact electrode is formed on the fourth electrode region; A common electrode is formed in electrical connection with the first n-type 4H-SiC layer.

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