A heterojunction photodetector and a preparation method thereof

Abstract

The application discloses a kind of heterojunction photoelectric detectors and preparation method thereof.The detector includes: substrate;Semiconductor epitaxial structure, at least including channel layer being arranged on the substrate and being located on the barrier layer of channel layer;Wherein, the thickness and component of the barrier layer are configured so that no two-dimensional electron gas is generated at the heterojunction interface between the channel layer and the barrier layer;First electrode and second electrode, set in the semiconductor epitaxial structure and electrically connected with the two-dimensional electron gas, constitute the electrical input end and output end of the heterojunction photoelectric detector.By configuring the thickness and component of the barrier layer so that no two-dimensional electron gas is generated in the channel, the damage of etching process to the channel is avoided, and the ultraviolet detector with extremely low dark current, high photocurrent density and no need to rely on etching process to deplete the channel is realized.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano manufacturing technology, specifically relating to a heterojunction photodetector and its fabrication method. Background Technology

[0002] Gallium nitride (GaN) and its related III-V group nitride materials (such as AlGaN and InGaN) possess wide bandgap, high breakdown field, high electron mobility, and excellent radiation resistance, making them widely used in high-frequency, high-power electronic devices. In recent years, with the rapid development of deep ultraviolet communication, ultraviolet imaging, flame detection, biofluorescence recognition, space ultraviolet remote sensing, and military early warning systems, the demand for photodetectors operating in the ultraviolet band (200–365 nm) with high responsivity, high speed, wide dynamic range, and high stability has been continuously increasing.

[0003] As a core electronic device that converts light signals into electrical signals, the photodetector's working principle is mainly based on the photoelectric effect, which means that after a semiconductor material absorbs photon energy, its internal conductivity or potential changes, thereby generating a measurable electrical signal. However, photodetectors provided by related technologies have drawbacks such as high dark current, low photocurrent density, and excessive reliance on etching techniques.

[0004] Therefore, there is an urgent need to provide a heterojunction photodetector and its fabrication method to meet the requirements of high detectivity applications and extremely low dark current and high photocurrent density. Summary of the Invention

[0005] The main objective of this invention is to provide a heterojunction photodetector and its fabrication method to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: One embodiment of the present invention provides a heterojunction photodetector, the heterojunction photodetector comprising: Substrate; A semiconductor epitaxial structure, the semiconductor epitaxial structure including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition of the barrier layer are configured such that no two-dimensional electron gas is generated at the heterojunction interface between the channel layer and the barrier layer. The first electrode and the second electrode are disposed on the semiconductor epitaxial structure and electrically connected to the two-dimensional electron gas, forming the electrical input and output terminals of the heterojunction photodetector.

[0007] In a preferred embodiment, both the first electrode and the second electrode are ohmic contact electrodes; the heterojunction photodetector is an ohmic thin barrier ultraviolet detector, and further includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode and the second electrode to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer and a capping layer. The lower end of the first electrode is disposed on the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer.

[0008] In a preferred embodiment, the first electrode is a Schottky contact electrode, and the second electrode is an ohmic contact electrode; the heterojunction photodetector is a Schottky-type thin barrier ultraviolet detector, and further includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first and second electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer, and a capping layer. The lower end of the first electrode is disposed on the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; or, the first electrode penetrates the capping layer, the barrier layer, and the insertion layer, and its lower end is disposed within the channel layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; or, the first electrode penetrates the capping layer, the barrier layer, and the insertion layer, and its lower end is disposed within the channel layer, and its upper end has a lateral extension portion, the lateral extension portion covering the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer.

[0009] In a preferred embodiment, a third electrode is further included, wherein the first electrode is a Schottky contact electrode, and the second and third electrodes are ohmic contact electrodes; the heterojunction photodetector is a hybrid anode type thin barrier ultraviolet detector, and further includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first and second electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer, and a capping layer; The lower end of the first electrode is disposed on the upper surface of the capping layer, and the lower end is also provided with a receiving portion; the upper end of the third electrode is disposed in the receiving portion, and its lower end penetrates the capping layer and is disposed in the barrier layer; the second electrode penetrates the capping layer, and its lower end is disposed in the barrier layer.

[0010] In a preferred embodiment, a third electrode is further included, wherein the first and second electrodes are ohmic contact electrodes and the third electrode is a Schottky contact electrode; the heterojunction photodetector is a HEMT device-type thin barrier ultraviolet detector, and an insulating dielectric layer is further included, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first, second, and third electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer, and a capping layer; The first electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; the lower end of the third electrode is disposed on the upper surface of the capping layer.

[0011] An embodiment of the present invention provides a method for fabricating a heterojunction photodetector, comprising: S10. Provide a substrate; form a semiconductor epitaxial layer on the substrate, the semiconductor epitaxial layer including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition of the barrier layer are configured such that no two-dimensional electron gas is generated at the heterojunction interface formed by the channel layer and the barrier layer. S20. An electrode is formed in the semiconductor epitaxial layer to form a heterojunction photodetector.

[0012] In a preferred embodiment, the substrate is a silicon carbide substrate, the semiconductor epitaxial layer further includes an AlN space layer and a GaN capping layer, the channel layer is a GaN channel layer, and the barrier layer is an AlGaN barrier layer. The formation of the semiconductor epitaxial layer on the substrate includes: A semiconductor epitaxial layer is formed by sequentially growing a GaN channel layer, an AlN space layer, an AlGaN barrier layer, and a GaN capping layer on a silicon carbide substrate using the MOCVD process.

[0013] In a preferred embodiment, the thickness of the GaN channel layer ranges from 10nm to 100nm, the thickness of the AlN space layer ranges from 0.5nm to 10nm, the thickness of the AlGaN barrier layer ranges from 1nm to 30nm, and the thickness of the GaN capping layer ranges from 0.5nm to 5nm.

[0014] In a preferred embodiment, S20 includes: S21. Perform active region isolation processing on the semiconductor epitaxial layer; S22. An electrode is formed in the ohmic region by vapor deposition of ohmic metal and annealing.

[0015] In a preferred embodiment, S21 includes performing active region isolation on the semiconductor epitaxial layer using ICP etching or ion implantation isolation processes, with an etching depth ranging from 30nm to 300nm. S22 includes: defining an ohmic region by photolithography; depositing a metal layer comprising at least one of Ti, Al, Ni and Au in the ohmic region; and annealing the metal layer in a nitrogen atmosphere to form an electrode with an ohmic contact.

[0016] Compared with existing technologies, the advantages of this invention are as follows: By configuring the thickness and composition of the barrier layer, no two-dimensional electron gas is generated at the heterojunction interface, eliminating the need for complex etching processes to remove the channel or to introduce a P-GaN layer and F ion treatment, thus simplifying the fabrication process. The dark current of the device is only related to the epitaxial parameters (barrier layer thickness and composition). The thin barrier design depletes the two-dimensional electron gas, avoiding surface defects caused by etching. The dark current can easily reach pA or even lower, meaning the dark current is extremely low and easily controlled. By avoiding damage to the channel during etching, the integrity of the channel material and high electron mobility are preserved, resulting in extremely high photocurrent density. Based on the extremely low dark current and extremely high photocurrent density, the device achieves an extremely high photocurrent-to-dark-current ratio and detectivity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the heterojunction epitaxial structure in one embodiment of this application; Figure 2 This is a schematic diagram of the heterojunction epitaxial structure including the capping layer in one embodiment of this application; Figure 3 This is a schematic diagram of a heterojunction epitaxial structure containing an insertion layer in one embodiment of this application; Figure 4 This is a schematic diagram of a heterojunction epitaxial structure including a cap layer and an insertion layer in one embodiment of this application; Figure 5 This is a schematic diagram of the structure of an ohmic thin barrier ultraviolet detector in one embodiment of this application; Figure 6 This is a schematic diagram of the structure of a horizontal contact Schottky-type thin barrier ultraviolet detector according to one embodiment of this application; Figure 7This is a schematic diagram of the structure of a vertically contacted Schottky-type thin barrier ultraviolet detector according to one embodiment of this application; Figure 8 This is a schematic diagram of the structure of a groove-contact Schottky-type thin barrier ultraviolet detector according to one embodiment of this application; Figure 9 This is a schematic diagram of the structure of a hybrid anode type thin barrier ultraviolet detector according to one embodiment of this application; Figure 10 This is a schematic diagram of the structure of a hybrid anode type thin barrier ultraviolet detector according to one embodiment of this application; Figure 11 This is a schematic diagram illustrating the variation of device responsivity in the 300nm-660nm range in one embodiment of this application; Figure 12 This is a schematic diagram of the device light-dark current ratio test in one embodiment of this application; Figure 13 This is a schematic diagram of a linear IV test under different light intensities in one embodiment of this application; Figure 14 This is a schematic diagram illustrating the relationship between the detectivity and light intensity of the device in one embodiment of this application; Figure 15 This is a schematic flowchart of the fabrication method of a heterojunction photodetector according to one embodiment of this application.

[0019] Illustration: 101, Substrate; 102, Channel layer; 103, Barrier layer; 104, Capping layer; 105, Insertion layer; 106, Insulating dielectric layer; 107, Electrical isolation layer; 108, First electrode; 109, Second electrode; 110, Third electrode. Detailed Implementation

[0020] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0021] In related technologies, to address the technical requirements mentioned in the background, AlGaN / GaN dual-channel device structures, P-GaN device structures, or F-ion treatment techniques are typically employed to deplete the two-dimensional electron gas in the channel to reduce dark current. Specifically: 1. AlGaN / GaN dual-channel device structure. In the design, the upper channel barrier layer is thicker, resulting in a higher concentration of 2DEG, while the lower channel barrier layer is thinner. The upper channel layer is removed using etching technology, allowing the etched area to deplete the 2DEG, thus exhibiting low dark current in the dark.

[0022] 2. P-GaN Device Structure. A P-GaN layer is epitaxially grown on the barrier layer to deplete the 2DEG in the channel. The P-GaN outside the gate is removed using etching. The presence of the gate P-GaN depletes the 2DEG below the gate, thus reducing dark current.

[0023] 3. F-ion treatment technology. This involves treating the barrier layer with F-ions to deplete the 2DEG in the channel.

[0024] However, the AlGaN / GaN dual-channel device structure inevitably suffers channel damage due to etching technology, reducing the device's photocurrent density. Furthermore, the etched surface exhibits significant defects, limiting the dark current to the microampere (µA) level, failing to reach pA or even lower. While the P-GaN device structure, by retaining the P-GaN gate, can reduce dark current to the pA level, it still suffers from low photocurrent density and places extremely high demands on etching technology, hindering its widespread adoption. F-ion treatment technology also introduces channel damage, resulting in low photocurrent. In summary, these technologies, when applied to ultraviolet photodetector applications, have not resolved the shortcomings of high dark current, low photocurrent density, and excessive reliance on etching technology leading to damage.

[0025] To address the aforementioned problems in related technologies, taking AlGaN / GaN heterojunctions as an example, spontaneous polarization and piezoelectric polarization exist in AlGaN / GaN heterojunctions, resulting in a two-dimensional electron gas at the interface. This application utilizes a heterojunction photodetector and its fabrication method, employing a thin-barrier epitaxial structure design. By reducing the Al composition and thickness of the barrier layer, the generation of a two-dimensional electron gas in the channel is eliminated, achieving a photodetector with extremely low dark current, high photocurrent density, and no etching process required. In practical applications, the technical solution provided in this application can also be applied to other semiconductors such as GaAs. The structure of the heterojunction photodetector will be described first, followed by its fabrication method.

[0026] Example 1 This embodiment provides a heterojunction photodetector, which includes: Substrate; A semiconductor epitaxial structure, the semiconductor epitaxial structure including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition of the barrier layer are configured such that no two-dimensional electron gas is generated at the heterojunction interface between the channel layer and the barrier layer. The first electrode and the second electrode are disposed on the semiconductor epitaxial structure and electrically connected to the two-dimensional electron gas, forming the electrical input and output terminals of the heterojunction photodetector.

[0027] Specifically, the thickness and composition of the barrier layer ensure that the two-dimensional electron gas (2DEG) that would normally form naturally at the heterojunction interface due to polarization is not generated in a static state, thus physically eliminating the conductive channel in the dark state. In this case, as long as the thickness and composition of the barrier layer satisfy the physical constraint condition that prevents the generation of 2DEG at the interface, it is sufficient. This structural depletion design gives the detector naturally extremely high impedance when not exposed to light, fundamentally eliminating leakage channels caused by etching damage or ion implantation defects in related technologies, and providing the basis for extremely low dark current.

[0028] The first and second electrodes are located on the semiconductor epitaxial structure and penetrate the surface layer to interact with the heterojunction interface. It is important to note that, since no 2DEG is generated at the interface in the structural parameter configuration of barrier layer 4, the term "electrically connected to the two-dimensional electron gas" does not mean that the electrode is in direct physical contact with a high-concentration conductive channel, but rather that the electrode establishes a pathway with the interface region. When ultraviolet light irradiates the detector, photon energy excites electron-hole pairs in the thin barrier layer and channel layer. Photogenerated electrons are rapidly transported to the interface region under the influence of the electric field, instantly accumulating at the heterojunction interface to form a transient photogenerated conductive channel. At this time, the first and second electrodes can efficiently collect these photogenerated carriers through this electrical connection and form a photocurrent output in the external circuit.

[0029] The specific contact type of the first and second electrodes (e.g., ohmic contact or Schottky contact) is not limited here, as long as the collection and output functions of photogenerated carriers described above can be achieved. It should be understood that although the figure shows the layout of the two electrodes, in actual array applications, the number and arrangement of the electrodes can be flexibly adjusted according to specific requirements.

[0030] Taking the spontaneous polarization and piezoelectric polarization in AlGaN / GaN heterojunctions as an example, the above technical solution illustrates that a two-dimensional electron gas exists at the interface between the two. This embodiment abandons the approach of physically destroying or implanting ions to deplete channel carriers, instead addressing the physical nature of heterojunctions by adjusting the geometry (thickness) and material parameters of the barrier layer to prevent the generation of a two-dimensional electron gas in the channel. In III-V group nitride heterojunctions such as AlGaN / GaN, a high concentration of two-dimensional electron gas inevitably forms at the interface due to the spontaneous polarization and piezoelectric polarization effects. This technical solution utilizes the physical constraint of 2DEG areal density, thinning the barrier layer and adjusting its Al composition (reducing the Al composition and thickness of the barrier layer) to prevent the generation of a two-dimensional electron gas. The following is a detailed explanation: See Figure 1 , Figure 1 For heterojunction epitaxial structures, taking the AlxGa1-xN / GaN heterojunction as an example, the formula for calculating the two-dimensional electron gas is: in, The concentration of two-dimensional electron gas; The magnitude of the elementary charge; It is the relative permittivity; The polarization charge of AlxGa1-xN; This represents the polarization charge of GaN. As an intermediate variable; is the dielectric constant of barrier layer 103 (AlxGa1-xN), and its magnitude is related to the Al composition x in barrier layer 103; The thickness of the barrier layer 103 (AlxGa1-xN) is given. The surface potential of barrier layer 103; The energy difference between the two-dimensional electron gas quantum well and the Fermi level; The band order difference between AlxGa1-xN and GaN; The band gap of AlxGa1-xN is related to the composition x of Al; The bandgap of AlN material is typically 6.026 eV; This represents the bandgap of GaN materials, typically 3.39 eV. The piezoelectric polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of GaN; The formula clearly shows the concentration of two-dimensional electron gas. With a barrier layer thickness of 103 There is a positive correlation, and the Al composition in the barrier layer 103 also directly affects the polarization charge and dielectric constant. Therefore, when the thickness of the barrier layer 103 is deliberately reduced, and the Al composition in the barrier layer 103 is simultaneously reduced, the third term in the formula ( The absolute value of ) will increase significantly, enough to completely offset the polarization-induced charge of the first two terms, in addition to the first term It will also decrease as the Al content decreases, thus preventing the generation of two-dimensional electron gas in the channel.

[0031] It should be understood that although this embodiment uses AlGaN / GaN heterojunction as an example for illustration, in other embodiments, this principle is also applicable to other III-V group nitride heterojunction systems such as InAlN / GaN and AlScN / GaN, as long as the thickness and composition of the barrier layer 103 are configured such that no charge carriers are generated in the channel.

[0032] See Figure 2 , Figure 2 For a heterojunction (including a capping layer 104) epitaxial structure, taking an AlGaN / GaN heterojunction with GaN as the capping layer 104 as an example, the formula for calculating the two-dimensional electron gas is: in, The concentration of two-dimensional electron gas; The magnitude of the elementary charge; It is the relative permittivity; The polarization charge of AlxGa1-xN; This represents the polarization charge of GaN. As an intermediate variable; is the dielectric constant of barrier layer 103 (AlxGa1-xN), and its magnitude is related to the Al composition x in barrier layer 103; The thickness of the barrier layer 103 (AlxGa1-xN) is given. The surface potential of barrier layer 103; The energy difference between the two-dimensional electron gas quantum well and the Fermi level; The band order difference between AlxGa1-xN and GaN; The band gap of AlxGa1-xN is related to the composition x of Al; The bandgap of AlN material is typically 6.026 eV; This represents the bandgap of GaN materials, typically 3.39 eV. The piezoelectric polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of GaN; See Figure 3 , Figure 3 For a heterojunction (including insertion layer 105) epitaxial structure, taking an AlGaN / GaN heterojunction with AlN as the insertion layer 105 as an example, the formula for calculating the two-dimensional electron gas is: in, The concentration of two-dimensional electron gas; The magnitude of the elementary charge; It is the relative permittivity; The polarization charge of AlxGa1-xN; This represents the polarization charge of GaN. The polarization charge of AlN; As an intermediate variable; The dielectric constant of the insertion layer 105 (AlN); is the dielectric constant of barrier layer 103 (AlxGa1-xN), and its magnitude is related to the Al composition x in barrier layer 103; The thickness of the insertion layer 105 (AlN); The thickness of the barrier layer 103 (AlxGa1-xN) is given. The surface potential of barrier layer 103; The energy difference between the two-dimensional electron gas quantum well and the Fermi level; The band order difference between AlxGa1-xN and AlN; The band order difference between AlN and GaN; The band gap of AlxGa1-xN is related to the composition x of Al; The bandgap of AlN material is typically 6.026 eV; This represents the bandgap of GaN materials, typically 3.39 eV. The piezoelectric polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of GaN; The piezoelectric polarization intensity of AlN; The spontaneous polarization intensity of AlN; See Figure 4 , Figure 4 For a heterojunction (including capping layer 104 and insertion layer 105) epitaxial structure, taking an AlGaN / GaN heterojunction as an example, with GaN as capping layer 104 and AlN as insertion layer 105, the formula for calculating the two-dimensional electron gas is: in, The concentration of two-dimensional electron gas; The magnitude of the elementary charge; It is the relative permittivity; The polarization charge of AlxGa1-xN; This represents the polarization charge of GaN. The polarization charge of AlN; As an intermediate variable; The dielectric constant of the insertion layer 105 (AlN); is the dielectric constant of barrier layer 103 (AlxGa1-xN), and its magnitude is related to the Al composition x in barrier layer 103; The thickness of the insertion layer 105 (AlN); The thickness of the barrier layer 103 (AlxGa1-xN) is given. The surface potential of barrier layer 103; The energy difference between the two-dimensional electron gas quantum well and the Fermi level; The band order difference between AlxGa1-xN and AlN; The band order difference between AlxGa1-xN and GaN; The band order difference between AlN and GaN; The band gap of AlxGa1-xN is related to the composition x of Al; The bandgap of AlN material is typically 6.026 eV; This represents the bandgap of GaN materials, typically 3.39 eV. The piezoelectric polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of AlxGa1-xN; The spontaneous polarization intensity of GaN; The piezoelectric polarization intensity of AlN; The spontaneous polarization intensity of AlN; Through the above structural design, the heterojunction photodetector of this embodiment achieves extremely low dark current in the dark state without relying on any subsequent etching damage. In specific applications, those skilled in the art can select the substrate material, epitaxial layer combination, and electrode configuration according to the specific detection band and response speed requirements, while ensuring that 2DEG is not generated.

[0033] The heterojunction photodetector protected in this embodiment is an ultraviolet detector. Furthermore, to facilitate signal detection at specific wavelengths, the bandgap of the material can be adjusted by regulating the composition of the metal elements in the barrier layer 103 to respond to different wavelengths. The formula for calculating the bandgap of the nitride alloy material is as follows: in, It is a component of metallic elements. It is the bending constant, which is usually taken as 1 eV for AlGaN.

[0034] Therefore, the technical solution provided in this embodiment, by configuring the thickness and composition of the barrier layer 103, prevents the generation of two-dimensional electron gas at the heterojunction interface, eliminating the need for complex etching processes to remove the channel or to introduce a P-GaN layer and F ion treatment, thus simplifying the fabrication process. The device's dark current is only related to the epitaxial parameters (barrier layer thickness and composition). The thin barrier design prevents the generation of two-dimensional electron gas in the channel, avoiding surface defects caused by etching. The dark current can easily reach pA or even lower, meaning it is extremely low and easily controlled. By avoiding damage to the channel from the etching process, the integrity of the channel material and high electron mobility are preserved, resulting in a very high photocurrent density. Based on the extremely low dark current and extremely high photocurrent density, the device achieves an extremely high photocurrent-to-dark-current ratio and detectivity. By adjusting the metal element composition in the alloy material such as the barrier layer 103, the bandgap of the material can be changed, thereby responding to ultraviolet light of different wavelengths and applying it to specific detection scenarios.

[0035] In one embodiment, the first electrode 108 and the second electrode 109 are both ohmic contact electrodes; the heterojunction photodetector is an ohmic thin barrier ultraviolet detector, and also includes an insulating dielectric layer 106, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode 108 and the second electrode 109 to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer 102, an insertion layer 105, a barrier layer 103, and a capping layer 104; The lower end of the first electrode 108 is disposed on the upper surface of the capping layer 104; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103.

[0036] As an example, see Figure 5In an ohmic thin-barrier ultraviolet detector, from bottom to top, the components are: a. Substrate 101 (any one of SiC, Si, sapphire, GaN, AlN, or diamond); b. Channel layer 102 (at least one of GaN, InGaN, AlGaN, or AlInGaN); c. Insertion layer 105 (AlN, InAlAs, InGaAlAs, InP, or InGaAs). The insertion layer 105 may be added or omitted depending on the specific application. d. Barrier layer 103 (at least one of AlGaN, InAlN, AlN, AlScN, or AlInGaN); e. Capping layer 104 (AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs). The capping layer 104 may be added or omitted depending on the specific application. f. First electrode 108 and second electrode 109 (both in ohmic contact form); g. Insulating dielectric layer 106 (Si3N4, SiO2, Al2O3, or HfO2). The insulating dielectric layer 106 may be added or omitted depending on the specific application; In one embodiment, the first electrode 108 is a Schottky contact electrode, and the second electrode 109 is an ohmic contact electrode; the heterojunction photodetector is a Schottky-type thin barrier ultraviolet detector, and further includes an insulating dielectric layer 106, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode 108 and the second electrode 109 to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer 102, an insertion layer 105, a barrier layer 103, and a capping layer 104; The lower end of the first electrode 108 is disposed on the upper surface of the capping layer 104; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103; or, the first electrode 108 penetrates the capping layer 104, the barrier layer 103, and the insertion layer 105, and its lower end is disposed within the channel layer 102; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103; or, the first electrode 108 penetrates the capping layer 104, the barrier layer 103, and the insertion layer 105, and its lower end is disposed within the channel layer 102, and its upper end has a lateral extension portion, which covers the upper surface of the capping layer 104; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103.

[0037] Schottky-type thin barrier ultraviolet detectors can be considered to include vertical contact Schottky, horizontal contact Schottky, and groove contact Schottky.

[0038] As an example, see Figure 6 , Figure 6The structure of this horizontal contact Schottky-type thin barrier ultraviolet detector device, from bottom to top, consists of: a. Substrate 101: SiC, Si, sapphire, GaN, AlN, or diamond; b. Channel layer 102: at least one of GaN, InGaN, AlGaN, and AlInGaN; c. Insertion layer 105: AlN, InAlAs, InGaAlAs, InP, or InGaAs, which may be added or omitted depending on the specific application. d. Barrier layer 103: AlGaN, InAlN, AlN, AlScN, or AlInGaN; e. Capping layer 104: AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs, which may be added or omitted depending on the specific application; f. Ohmic contact layer (second electrode 109); g. Schottky contact layer (first electrode 108); h. Insulating dielectric layer 106: Si3N4, SiO2, Al2O3, or HfO2, which may be added or omitted depending on the specific application.

[0039] As another example, see Figure 7 , Figure 7 This is the structure of a thin-barrier ultraviolet detector (vertical contact Schottky type) device, from bottom to top: a. Substrate 101: SiC, Si, sapphire, GaN, AlN, diamond, etc.; b. Channel layer 102: at least one of GaN, InGaN, AlGaN, and AlInGaN; c. Insertion layer 105: AlN, InAlAs, InGaAlAs, InP, or InGaAs, which may be added or omitted depending on the specific application; d. Barrier layer 103: AlGa... N, InAlN, AlN, AlScN, or AlInGaN; e. Capping layer 104: AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs, which may be added or omitted depending on the specific application; f. Ohmic contact layer (second electrode 109); g. Schottky contact layer (first electrode 108); h. Insulating dielectric layer 106: Si3N4, SiO2, Al2O3, or HfO2, which may be added or omitted depending on the specific application.

[0040] As yet another example, see Figure 8 , Figure 8This is the structure of a thin-barrier ultraviolet detector (groove contact Schottky type) device, from bottom to top: a. Substrate 101: SiC, Si, sapphire, GaN, AlN, diamond, etc.; b. Channel layer 102: at least one of GaN, InGaN, AlGaN, and AlInGaN; c. Insertion layer 105: AlN, InAlAs, InGaAlAs, InP, or InGaAs, which may be added or omitted depending on the specific application; d. Barrier layer 103: AlGa... N, InAlN, AlN, AlScN, or AlInGaN; e. Capping layer 104: AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs, which may be added or omitted depending on the specific application; f. Ohmic contact layer (second electrode 109); g. Schottky contact layer (first electrode 108); h. Insulating dielectric layer 106: Si3N4, SiO2, Al2O3, or HfO2, which may be added or omitted depending on the specific application.

[0041] In one embodiment, a third electrode 110 is further included, the first electrode 108 is a Schottky contact electrode, and the second electrode 109 and the third electrode 110 are ohmic contact electrodes; the heterojunction photodetector is a hybrid anode type thin barrier ultraviolet detector, and further includes an insulating dielectric layer 106, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode 108 and the second electrode 109 to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer 102, an insertion layer 105, a barrier layer 103, and a capping layer 104; The lower end of the first electrode 108 is disposed on the upper surface of the capping layer 104, and the lower end is also provided with a receiving portion; the upper end of the third electrode 110 is disposed in the receiving portion, and its lower end penetrates the capping layer 104 and is disposed in the barrier layer 103; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed in the barrier layer 103.

[0042] As an example, see Figure 9 , Figure 9The structure of this thin-barrier ultraviolet detector (hybrid anode type) device, from bottom to top, consists of: a. Substrate 101: SiC, Si, sapphire, GaN, AlN, diamond, etc.; b. Channel layer 102: at least one of GaN, InGaN, AlGaN, and AlInGaN; c. Insertion layer 105: AlN, InAlAs, InGaAlAs, InP, or InGaAs, which may be added or omitted depending on the specific application; d. Barrier layer 103: AlGaN, InAl... N, AlN, AlScN, or AlInGaN; e. Capping layer 104: AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs, which may be added or omitted depending on the specific application; f. Ohmic contact layer (second electrode 109 and third electrode 110); g. Schottky contact layer (first electrode 108); h. Insulating dielectric layer 106: Si3N4, SiO2, Al2O3, or HfO2, which may be added or omitted depending on the specific application.

[0043] In one embodiment, a third electrode 110 is further included, wherein the first electrode 108 and the second electrode 109 are ohmic contact electrodes, and the third electrode 110 is a Schottky contact electrode; the heterojunction photodetector is a HEMT device-type thin barrier ultraviolet detector, and further includes an insulating dielectric layer 106, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode 108, the second electrode 109, and the third electrode 110 to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer 102, an insertion layer 105, a barrier layer 103, and a capping layer 104; The first electrode 108 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103; the second electrode 109 penetrates the capping layer 104, and its lower end is disposed within the barrier layer 103; the lower end of the third electrode 110 is disposed on the upper surface of the capping layer 104.

[0044] As an example, see Figure 10 , Figure 10This is a thin-barrier ultraviolet detector (HEMT device type) structure, from bottom to top: a. Substrate 101: SiC, Si, sapphire, GaN, AlN, diamond, etc.; b. Channel layer 102: at least one of GaN, InGaN, AlGaN, and AlInGaN; c. Insertion layer 105: AlN, InAlAs, InGaAlAs, InP, or InGaAs, which may be added or omitted depending on the specific application; d. Barrier layer 103: AlGaN, InAs... lN, AlN, AlScN, or AlInGaN; e. Capping layer 104: AlGaAs, InGaAs, GaAs, InP, GaN, AlGaN, or InAs, which may be added or omitted depending on the specific application; f. Ohmic contact layer (first electrode 108 and second electrode 109); g. Schottky contact layer (third electrode 110); h. Insulating dielectric layer 106: Si3N4, SiO2, Al2O3, or HfO2, which may be added or omitted depending on the specific application; For applications of thin barrier ultraviolet detector (HEMT) structures: Conventional heterojunction detectors suffer from persistent photoconductivity, resulting in slow device response. HEMT structures, by applying an additional voltage to the gate, provide additional transport paths for holes on the surface, thereby accelerating the device's response.

[0045] In addition, Figures 5 to 10 It also includes an electrical isolation layer 107 formed by ion implantation isolation or surface etching isolation.

[0046] Example 2 See Figure 15 This embodiment provides a method for fabricating a heterojunction photodetector, including: S10. Provide a substrate; form a semiconductor epitaxial layer on the substrate, the semiconductor epitaxial layer including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition (5nm / 18%) of the barrier layer are configured such that the two-dimensional electron gas at the heterojunction interface formed by the channel layer and the barrier layer is in a depleted state. S20. An electrode is formed in the semiconductor epitaxial layer to form a heterojunction photodetector. It can be assumed that the plane of the electrode away from the substrate has contacts for setting electrode leads through the contacts.

[0047] The thin barrier design of this application completes the depletion configuration of 2DEG during the material growth stage, eliminating the need for subsequent etching thinning or ion implantation destruction steps. This avoids leakage channels caused by etching damage, enabling the dark current to break through to a lower order of magnitude, while ensuring the efficient transport of photogenerated carriers and achieving extremely high photocurrent density.

[0048] In one embodiment, the substrate is a silicon carbide substrate, the semiconductor epitaxial layer further includes an AlN space layer (i.e., an insertion layer) and a GaN capping layer, the channel layer is a GaN channel layer, the barrier layer is an AlGaN barrier layer, and the formation of the semiconductor epitaxial layer on the substrate includes: A semiconductor epitaxial layer is formed by sequentially growing a GaN channel layer, an AlN space layer, an AlGaN barrier layer, and a GaN capping layer on a silicon carbide substrate using the MOCVD process.

[0049] In one embodiment, the thickness of the GaN channel layer ranges from 10nm to 100nm, the thickness of the AlN space layer ranges from 0.5nm to 10nm, the thickness of the AlGaN barrier layer ranges from 1nm to 30nm, and the thickness of the GaN capping layer ranges from 0.5nm to 5nm.

[0050] In one embodiment, S20 includes: S21. Perform active region isolation processing on the semiconductor epitaxial layer; S22. An electrode is formed in the ohmic region by vapor deposition of ohmic metal and annealing.

[0051] In one embodiment, S21 includes performing active region isolation on the semiconductor epitaxial layer using ICP etching or ion implantation isolation processes, with an etching depth ranging from 30nm to 300nm. S22 includes: defining an ohmic region by photolithography; depositing a metal layer comprising at least one of Ti, Al, Ni and Au in the ohmic region; and annealing the metal layer in a nitrogen atmosphere to form an electrode with an ohmic contact.

[0052] As an example, a method for fabricating a heterojunction photodetector (thin barrier AlGaN / GaN heterojunction ultraviolet detector) is provided, comprising: S1. Using MOCVD process, Fe-GaN buffer layer with a thickness of 100-500nm, unintentionally doped GaN with a thickness of 100-600nm, GaN channel layer with a thickness of 10-100nm, AlN space layer with a thickness of 1-10nm, AlGaN barrier layer with a thickness of 1-30nm, and GaN capping layer with a thickness of 1-5nm are sequentially grown on silicon carbide substrate to form a semiconductor epitaxial layer.

[0053] S2. Active region isolation is performed on the semiconductor epitaxial layer by means of ICP etching process, etc., with an etching depth of 30-300nm.

[0054] S3. Define the ohmic region using photolithography, deposit ohmic metals Ti / Al / Ni / Au in the ohmic region, and then anneal in a nitrogen atmosphere. This creates an ohmic contact between the transistor electrode and the semiconductor layer.

[0055] The following shows some test results for the device. First, the device responsivity changes within the 290nm-540nm range. The test results are as follows: Figure 11 As shown, the device is excited at 360nm for GaN and at 330nm for AlGaN.

[0056] The device's light-dark current ratio test results are as follows: Figure 12 As shown, at a wavelength of 360 nm, the device achieves a maximum photocurrent-to-dark-current ratio of 3 × 10¹⁰. See also... Figure 13 This demonstrates the IV characteristics of the device under different illumination intensities, with a maximum current density reaching 271 mA / mm². (See also...) Figure 14 The relationship between the device's detectivity and light intensity was demonstrated, with the device achieving a maximum detectivity of 5 × 10²⁰ Jones.

[0057] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this document is not intended to limit the invention to the specific embodiments disclosed for carrying out the invention, but rather to include all embodiments falling within the scope of the appended claims.

Claims

1. A heterojunction photodetector, characterized in that, The heterojunction photodetector includes: Substrate; A semiconductor epitaxial structure, the semiconductor epitaxial structure including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition of the barrier layer are configured such that no two-dimensional electron gas is generated at the heterojunction interface between the channel layer and the barrier layer. The first electrode and the second electrode are disposed on the semiconductor epitaxial structure and electrically connected to the two-dimensional electron gas, forming the electrical input and output terminals of the heterojunction photodetector.

2. The heterojunction photodetector according to claim 1, characterized in that, Both the first electrode and the second electrode are ohmic contact electrodes; the heterojunction photodetector is an ohmic thin barrier ultraviolet detector, and also includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first electrode and the second electrode to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer and a capping layer. The lower end of the first electrode is disposed on the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer.

3. The heterojunction photodetector according to claim 1, characterized in that, The first electrode is a Schottky contact electrode, and the second electrode is an ohmic contact electrode; the heterojunction photodetector is a Schottky-type thin barrier ultraviolet detector, and also includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first and second electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer, and a capping layer. The lower end of the first electrode is disposed on the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; or, the first electrode penetrates the capping layer, the barrier layer, and the insertion layer, and its lower end is disposed within the channel layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; or, the first electrode penetrates the capping layer, the barrier layer, and the insertion layer, and its lower end is disposed within the channel layer, and its upper end has a lateral extension portion, the lateral extension portion covering the upper surface of the capping layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer.

4. The heterojunction photodetector according to claim 1, characterized in that, It also includes a third electrode, the first electrode is a Schottky contact electrode, and the second and third electrodes are ohmic contact electrodes; the heterojunction photodetector is a hybrid anode type thin barrier ultraviolet detector, and also includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first and second electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer and a capping layer; The lower end of the first electrode is disposed on the upper surface of the capping layer, and the lower end is also provided with a receiving portion; the upper end of the third electrode is disposed in the receiving portion, and its lower end penetrates the capping layer and is disposed in the barrier layer; the second electrode penetrates the capping layer, and its lower end is disposed in the barrier layer.

5. The heterojunction photodetector according to claim 1, characterized in that, It also includes a third electrode, wherein the first and second electrodes are ohmic contact electrodes and the third electrode is a Schottky contact electrode; the heterojunction photodetector is a HEMT device-type thin barrier ultraviolet detector, and also includes an insulating dielectric layer, which covers the upper surface of the semiconductor epitaxial structure and extends upward along the sidewalls of the first, second, and third electrodes to cover their sides; the semiconductor epitaxial structure includes, from bottom to top, a channel layer, an insertion layer, a barrier layer, and a capping layer; The first electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; the second electrode penetrates the capping layer, and its lower end is disposed within the barrier layer; the lower end of the third electrode is disposed on the upper surface of the capping layer.

6. A method for fabricating a heterojunction photodetector, characterized in that, include: S10. Provide a substrate; form a semiconductor epitaxial layer on the substrate, the semiconductor epitaxial layer including at least a channel layer disposed on the substrate and a barrier layer disposed above the channel layer; wherein the thickness and composition of the barrier layer are configured such that no two-dimensional electron gas is generated at the heterojunction interface formed by the channel layer and the barrier layer. S20. An electrode is formed in the semiconductor epitaxial layer to form a heterojunction photodetector.

7. The preparation method according to claim 6, characterized in that, The substrate is a silicon carbide substrate, the semiconductor epitaxial layer further includes an AlN space layer and a GaN capping layer, the channel layer is a GaN channel layer, the barrier layer is an AlGaN barrier layer, and the formation of the semiconductor epitaxial layer on the substrate includes: A semiconductor epitaxial layer is formed by sequentially growing a GaN channel layer, an AlN space layer, an AlGaN barrier layer, and a GaN capping layer on a silicon carbide substrate using the MOCVD process.

8. The preparation method according to claim 7, characterized in that, The thickness of the GaN channel layer ranges from 10nm to 100nm, the thickness of the AlN space layer ranges from 0.5nm to 10nm, the thickness of the AlGaN barrier layer ranges from 1nm to 30nm, and the thickness of the GaN capping layer ranges from 0.5nm to 5nm.

9. The preparation method according to any one of claims 6-8, characterized in that, S20 includes: S21. Perform active region isolation processing on the semiconductor epitaxial layer; S22. An electrode is formed in the ohmic region by vapor deposition of ohmic metal and annealing.

10. The preparation method according to claim 9, characterized in that, S21 includes using ICP etching or ion implantation isolation processes to isolate the active region of the semiconductor epitaxial layer, with an etching depth ranging from 30nm to 300nm. S22 includes: defining an ohmic region by photolithography; depositing a metal layer comprising at least one of Ti, Al, Ni and Au in the ohmic region; and annealing the metal layer in a nitrogen atmosphere to form an electrode with an ohmic contact.

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