Graphene / gan / algan rectifier chip and preparation method thereof

Abstract

The graphene / GaN / AlGaN rectifier chip is characterized by comprising a Si substrate, an AlGaN layer and a GaN layer which are sequentially stacked from bottom to top; an ohmic cathode structure and a Schottky anode structure are arranged on the upper surface of the GaN layer; the Schottky anode structure comprises an isolation layer and a graphene layer, one end of the graphene layer is electrically connected with the isolation layer, the other end of the graphene layer is electrically connected with the GaN layer, and the graphene layer, the isolation layer and the GaN layer maintain the same potential.The graphene / GaN / AlGaN rectifier chip has the advantages of low flicker noise, high working current and the like.

Description

Technical Field

[0001] This invention belongs to the field of diode device technology, specifically relating to a graphene / GaN / AlGaN rectifier chip and its fabrication method. Background Technology

[0002] Schottky diodes hold an extremely important position in the semiconductor field. In recent years, due to advancements in processes and materials, Schottky diodes based on GaN heterojunction materials have achieved significant development. Gallium nitride (GaN), as one of the representatives of third-generation semiconductor materials, possesses stable chemical properties, high temperature resistance, and corrosion resistance, giving it inherent advantages in high-frequency, high-power, and radiation-resistant applications. Furthermore, GaN materials also have advantages such as strong critical breakdown electric field, high temperature resistance, and high saturated electron drift velocity, making them promising for applications in power electronics.

[0003] High electron mobility transistors (HEMTs) based on AlGaN / GaN heterojunctions have been widely used in the semiconductor field. These devices possess characteristics such as high reverse blocking voltage, low forward on-resistance, and high operating frequency, thus meeting the system requirements for higher power, higher frequency, and smaller size operation of semiconductor devices. However, they also have drawbacks such as high barrier inhomogeneity, lower frequency, higher flicker noise, lower current, and complex fabrication. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the present invention aims to provide a graphene / GaN / AlGaN rectifier chip that solves the problems of high barrier inhomogeneity and low frequency.

[0005] Another object of the present invention is to provide a method for fabricating a graphene / GaN / AlGaN rectifier chip.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A graphene / GaN / AlGaN rectifier chip includes a Si substrate, an AlGaN layer, and a GaN layer stacked sequentially from bottom to top; an ohmic cathode structure and a Schottky anode structure are disposed on the upper surface of the GaN layer; the Schottky anode structure includes an isolation layer and a graphene layer, one end of the graphene layer is electrically connected to the isolation layer, and the other end of the graphene layer is electrically connected to the GaN layer, and the graphene layer, the isolation layer, and the GaN layer maintain the same potential.

[0008] Preferably, the thickness of the AlGaN layer is 20–30 nm.

[0009] Preferably, the thickness of the GaN layer is 2–4 μm.

[0010] Preferably, the graphene layer has a length of 15-20 μm.

[0011] Preferably, the ohmic cathode structure is a first metal electrode forming an ohmic contact in the GaN layer, wherein the first metal electrode comprises one or more of Cr, Ti, Al, Au, Ag, and Pt.

[0012] Preferably, the length of the first metal electrode is 8-10 μm and the thickness is 30-35 nm.

[0013] Preferably, the isolation layer is a second electrode with an isolation effect formed on the GaN layer, and the second electrode includes one or more of Cr, Au, and Al2O3.

[0014] Preferably, the second electrode has a length of 5-7 μm and a thickness of 58-63 nm.

[0015] Preferably, the distance between the first metal electrode and the second electrode is 10 to 15 μm.

[0016] A graphene / GaN / AlGaN rectifier chip, the specific steps are as follows:

[0017] (1) Take an epitaxial high-resistivity silicon substrate, and use MOCVD equipment to grow an AlGaN layer and a GaN epitaxial layer on the epitaxial high-resistivity substrate to obtain an epitaxial wafer.

[0018] (2) Take a Ti / Al / Ni / Au multi-metal layer, deposit an ohmic contact structure by electron beam evaporation, and then anneal it at 550-650℃ for 25-35s in N2 atmosphere to obtain the first metal electrode forming the ohmic contact.

[0019] (3) Take the Al2O3 / Cr / Au layer, and prepare Schottky contacts by photolithography and electron beam evaporation to obtain a second electrode with isolation effect;

[0020] (4) Transfer the mechanically peeled graphene onto the GaN layer and make it directly contact the second electrode to obtain a graphene / GaN / AlGaN rectifier chip.

[0021] The present invention has the following advantages and beneficial effects compared with the prior art:

[0022] The present invention proposes a graphene / GaN / AlGaN rectifier chip with simple preparation steps. Its contact interface has a higher frequency, smaller barrier inhomogeneity, better surface flatness, lower flicker noise, and higher thermionic emission current, and has the advantages of low flicker noise and high operating current.

[0023] Compared to traditional AlGaN / GaN rectifier chips, electrons in N-polar GaN / AlGaN heterojunctions do not need to cross the AlGaN barrier layer, which changes the electron movement path and results in a shorter transit time, thus achieving a higher frequency. Furthermore, placing GaN on the surface simplifies the fabrication process.

[0024] Secondly, exfoliated graphene as an electrode has better interfacial properties and smaller barrier inhomogeneities, while also exhibiting better thermal stability and preventing tunneling effects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a graphene / GaN / AlGaN rectifier chip structure.

[0026] Figure 2 This is a schematic diagram of the substrate surface structure;

[0027] Figure 3 This is a schematic diagram of an epitaxial AlGaN layer structure on a substrate surface;

[0028] Figure 4 This is a schematic diagram of the epitaxial GaN layer structure on the surface of an AlGaN layer;

[0029] Figure 5 This is a schematic diagram of an ohmic cathode structure stacked on the surface of a GaN barrier layer.

[0030] Figure 6 This is a schematic diagram of the structure of an isolation layer deposited on the surface of a GaN barrier layer;

[0031] Figure 7 This is a schematic diagram of the structure for transferring graphene onto a GaN layer and an isolation layer.

[0032] Figure 8 This is a schematic diagram of a conventional AlGaN / GaN SBD rectifier chip structure;

[0033] Figure 9 Raman spectra of transferred graphene;

[0034] Figure 10 A comparison chart of IV curves for graphene / GaN / AlGaN rectifier chips and Ni / GaN / AlGaN rectifier chips;

[0035] The markings of the components in the attached diagram:

[0036] 1-Si substrate, 2-AlGaN layer, 3-GaN layer, 4-ohmic cathode structure, 5-isolation layer, 6-graphene layer. Detailed Implementation

[0037] The invention's objective will be further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described in detail here, but the implementation of the invention is not limited to the following embodiments.

[0038] A graphene / GaN / AlGaN rectifier chip includes a Si substrate 1, an AlGaN layer 2, a GaN layer 3, an ohmic cathode structure 4, and a Schottky anode structure; the Schottky anode structure includes an isolation layer 5 and a graphene layer 6.

[0039] From bottom to top, the structure consists of a Si substrate 1, an AlGaN layer 2, and a GaN layer 3. An isolation layer 5 is located on the left side of the upper surface of the GaN layer 3, an ohmic cathode structure 4 is located on the right side of the upper surface of the GaN layer 3, and a graphene layer 6 is located above the isolation layer 5 and the GaN layer 3, and is electrically connected to the isolation layer 5 and the GaN layer 3. All three layers maintain the same potential.

[0040] Example 1

[0041] This embodiment describes a method for fabricating a graphene / GaN / AlGaN rectifier chip:

[0042] (1) Take an epitaxial high-resistivity silicon substrate with a thickness of 500 μm, and grow an AlGaN layer and a GaN epitaxial layer on the epitaxial high-resistivity substrate using an MOCVD device to obtain an epitaxial wafer. The AlGaN layer has a thickness of 25 nm and the GaN layer has a thickness of 2 μm.

[0043] (2) Take a 3nmTi / 6nmAl / 6nmNi / 15nmAu multi-metal layer, deposit ohmic contacts by electron beam evaporation, and then anneal at 600℃ for 30s in N2 atmosphere to prepare the first metal electrode forming the ohmic contact. The thickness of the first metal electrode is 30nm.

[0044] (3) Take a 15nm Al2O3 / 10nm Cr / 33nm Au layer, prepare a Schottky contact by photolithography and electron beam evaporation, and prepare a second electrode with isolation effect. The thickness of the second electrode is 58nm.

[0045] (4) Transfer the mechanically peeled graphene onto the GaN layer and make direct contact with the second electrode to obtain a graphene / GaN / AlGaN rectifier chip.

[0046] Example 2

[0047] (1) Take an epitaxial high-resistivity silicon substrate with a thickness of 500 μm, and grow an AlGaN layer and a GaN epitaxial layer on the epitaxial high-resistivity substrate using an MOCVD device to obtain an epitaxial wafer. The AlGaN layer has a thickness of 20 nm and the GaN layer has a thickness of 3 μm.

[0048] (2) Take a 3nmTi / 6nmAl / 6nmNi / 17nmAu multi-metal layer, deposit an ohmic contact by electron beam evaporation, and then anneal it at 600℃ for 30s in N2 atmosphere to prepare the first metal electrode of the ohmic contact. The thickness of the first metal electrode is 32nm.

[0049] (3) Take a 15nm Al2O3 / 10nm Cr / 35nm Au layer, and prepare a Schottky contact by photolithography and electron beam evaporation to obtain a second electrode with isolation effect. The thickness of the second electrode is 60nm.

[0050] (4) Transfer the mechanically peeled graphene onto the GaN layer and make direct contact with the second electrode to obtain a graphene / GaN / AlGaN rectifier chip.

[0051] Example 3

[0052] (1) Take an epitaxial high-resistivity silicon substrate with a thickness of 500 μm, and grow an AlGaN layer and a GaN epitaxial layer on the epitaxial high-resistivity substrate using an MOCVD device to obtain an epitaxial wafer. The AlGaN layer has a thickness of 30 nm and the GaN layer has a thickness of 4 μm.

[0053] (2) Take a 3nmTi / 6nmAl / 6nmNi / 20nmAu multi-metal layer, deposit an ohmic contact at the ohmic contact using electron beam evaporation, and then anneal at 600℃ for 30s in N2 atmosphere to prepare the first metal electrode of the ohmic contact. The thickness of the first metal electrode is 35nm.

[0054] (3) Take a 15nm Al2O3 / 12nm Cr / 35nm Au layer, and prepare a Schottky contact by photolithography and electron beam evaporation to obtain a second electrode with isolation effect. The thickness of the second electrode is 62nm.

[0055] (4) Transfer the mechanically peeled graphene onto the GaN layer and make direct contact with the second electrode to obtain a graphene / GaN / AlGaN rectifier chip.

[0056] Figure 9 To transfer the Raman spectrum of graphene, by Figure 9 It can be seen that at 1580cm -1 and 2600cm -1 The presence of strong peaks nearby, corresponding to the G and 2D peaks of graphene respectively, indicates that the transferred graphene is high-quality graphene.

[0057] Figure 10 This is a comparison chart of the IV curves of graphene / GaN / AlGaN rectifier chips and Ni / GaN / AlGaN rectifier chips. Figure 10It is known that the graphene / GaN / AlGaN rectifier chip has a higher current under positive voltage compared to the Ni / GaN / AlGaN rectifier chip; electrons in the N-polar GaN / AlGaN heterojunction do not need to cross the AlGaN barrier layer, which changes the electron movement path and has a shorter transit time. Exfoliating graphene as an electrode improves the interface characteristics and barrier uniformity, while also providing better thermal stability. The graphene / GaN / AlGaN rectifier chip prepared in this invention has a higher frequency at the contact interface, smaller barrier non-uniformity, better surface flatness, lower flicker noise, and higher thermionic emission current, exhibiting advantages such as low flicker noise and high operating current.

[0058] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. A graphene / GaN / AlGaN rectifier chip, characterized in that, The device comprises a Si substrate, an AlGaN layer, and a GaN layer stacked sequentially from bottom to top. An ohmic cathode structure and a Schottky anode structure are disposed on the upper surface of the GaN layer. The Schottky anode structure includes an isolation layer and a graphene layer. One end of the graphene layer is electrically connected to the isolation layer, and the other end of the graphene layer is electrically connected to the GaN layer. The graphene layer, the isolation layer, and the GaN layer maintain the same potential.

2. The graphene / GaN / AlGaN rectifier chip according to claim 1, characterized in that, The thickness of the AlGaN layer is 20–30 nm.

3. The graphene / GaN / AlGaN rectifier chip according to claim 1, characterized in that, The thickness of the GaN layer is 2–4 μm.

4. The graphene / GaN / AlGaN rectifier chip according to claim 1, characterized in that, The graphene layer has a length of 15-20 μm.

5. A graphene / GaN / AlGaN rectifier chip according to claim 1, characterized in that, The ohmic cathode structure is a first metal electrode forming an ohmic contact in the GaN layer, wherein the first metal electrode comprises one or more of Cr, Ti, Al, Au, Ag, and Pt.

6. A graphene / GaN / AlGaN rectifier chip according to claim 5, characterized in that, The first metal electrode has a length of 8–10 μm and a thickness of 30–35 nm.

7. A graphene / GaN / AlGaN rectifier chip according to claim 5, characterized in that, The isolation layer is a second electrode with an isolation effect formed on the GaN layer, and the second electrode is one of Al2O3 / Au, Al2O3 / Cr or Al2O3 / Cr / Au.

8. A graphene / GaN / AlGaN rectifier chip according to claim 7, characterized in that, The second electrode has a length of 5–7 μm and a thickness of 58–63 nm.

9. A graphene / GaN / AlGaN rectifier chip according to claim 7, characterized in that, The distance between the first metal electrode and the second electrode is 10 to 15 μm.

10. A method for fabricating a graphene / GaN / AlGaN rectifier chip according to any one of claims 1-9, characterized in that, The specific steps are as follows: (1) Take an epitaxial high-resistivity silicon substrate, and use MOCVD equipment to grow an AlGaN layer and a GaN epitaxial layer on the epitaxial high-resistivity substrate to obtain an epitaxial wafer. (2) Take a Ti / Al / Ni / Au multi-metal layer, deposit an ohmic contact structure by electron beam evaporation, and then anneal it at 550-650℃ for 25-35s in N2 atmosphere to obtain the first metal electrode forming the ohmic contact. (3) Take the Al2O3 / Cr / Au layer, and prepare Schottky contacts by photolithography and electron beam evaporation to obtain a second electrode with isolation effect; (4) Transfer the mechanically peeled graphene onto the GaN layer and make it directly contact the second electrode to obtain a graphene / GaN / AlGaN rectifier chip.

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