A dual-channel SBD device with polarized junction and polarized doping structure and its preparation method

Abstract

The present invention relates to a dual-channel SBD device with a polarization junction and a polarization doping structure and a preparation method. The dual-channel SBD device comprises a dual-channel structure composed of a channel layer, an insertion layer, and a barrier layer stacked on a substrate, a polarization junction located on the channel structure, an ohmic contact anode provided on the surface of the polarization junction, a Schottky contact anode and an ohmic contact cathode respectively contacting the sidewalls of the first channel structure, the Schottky contact anode extending to the surface of the ohmic contact anode, a second barrier layer being a polarization doped AlGaN layer, the Al component of which gradually increases in a direction from the substrate to the channel layer, the polarization junction being composed of a polarization GaN layer and a p-type polarization doped AlGaN cap layer, the Al component of the AlGaN cap layer gradually decreasing in a direction from the substrate to the channel layer, the dual-channel SBD device having the characteristics of low turn-on voltage, low on-resistance, and high breakdown voltage, and being suitable for operation in high-temperature and high-pressure environments.

Description

Technical Field

[0001] The present invention relates to the technical field of SBD devices, and in particular to a double-channel SBD device with a polarization junction and polarization doping structure and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN) power devices leverage GaN's wide bandgap, high breakdown electric field, and high thermal conductivity. These devices offer advantages such as compact size, high power density, and fast switching speeds. The AlGaN / GaN heterojunction interface possesses a high-density two-dimensional electron gas. Lateral Schottky diodes (SBDs) with this AlGaN / GaN heterojunction exhibit extremely high mobility, making them suitable for high-frequency applications. They are currently widely used in consumer electronics, communications, and industrial control. Future device development will expand into emerging areas such as new energy, rail transit, and smart grids. To meet the demands of these emerging sectors, SBDs must operate in high-temperature and high-voltage environments while maintaining low losses and high switching characteristics.

[0003] Lower on-resistance and turn-on voltage can reduce losses and heat generation during operation. A higher breakdown voltage ensures device operation at high voltages. The AlGaN / GaN heterojunction in the SBD combines high mobility with a high concentration of two-dimensional electron gas, enabling high-frequency applications. However, due to electric field concentration, the breakdown voltage of GaN-based Schottky diodes falls far short of the theoretical limit of GaN. Furthermore, increasing the breakdown voltage is often accompanied by an increase in on-resistance. Therefore, maintaining a high breakdown voltage while minimizing on-resistance is a pressing issue. Summary of the Invention

[0004] In response to the technical problems existing in the prior art, the primary purpose of the present invention is to provide a dual-channel SBD device and a preparation method of a polarization junction and polarization doping structure with low turn-on voltage, low on-resistance and high breakdown voltage. The device is based on an AlGaN / GaN heterojunction and is provided with a dual-channel structure of a channel layer / insertion layer / barrier layer, wherein the second barrier layer is a polarization-doped AlGaN layer with a gradient Al composition, and the Al composition of the polarization-doped AlGaN barrier layer gradually increases in the direction from the substrate to the channel layer. The provision of the polarization-doped AlGaN barrier layer increases the connectivity between the two channels and reduces the on-resistance and turn-on voltage; a polarization junction consisting of a polarization GaN layer and a p-type polarization-doped AlGaN cap layer is provided on the dual-channel structure, which greatly solves the electric field concentration phenomenon and significantly improves the breakdown voltage. The breakdown voltage is determined by the following steps: the Al component of the AlGaN cap layer gradually decreases in the direction from the substrate to the channel layer; the polarized GaN layer is located on the polarized-doped AlGaN barrier layer; tensile strain is generated above the AlGaN barrier layer and compressive strain is generated below the polarized GaN layer, thereby generating hole gas at the interface between the two layers; the thickness of the polarized GaN layer is selected to be 20nm to 60nm. In a preferred embodiment, the thickness of the polarized GaN layer is selected to be 20nm to 30nm, which is the same as the thickness of the polarized-doped AlGaN barrier layer, so that the hole gas and the electron gas in the second channel have the same concentration (i.e., the two-dimensional electron gas concentration at the interface of the AlGaN barrier layer / GaN channel layer is the same as the hole concentration at the interface of the polarized GaN / polarized-doped AlGaN barrier layer), resulting in a charge compensation effect, thereby converting heterojunction breakdown into dielectric breakdown.

[0005] The present invention sets a P-type polarization doped AlGaN cap layer on the second barrier layer, in which the Al content gradually decreases in the direction from the substrate to the channel, instead of the traditional p-type GaN cap layer. The polarization doped cap layer is a high-concentration hole layer generated by the polarization effect. The holes are evenly distributed in this layer, showing the performance of a P-type semiconductor. Compared with conventional p-type GaN, the hole concentration generated by the polarization doping is 10 18 cm -3 , and the hole concentration does not change with temperature, it has high stability and is suitable for working in high temperature and high pressure environments.

[0006] On the other hand, the present invention adopts a hybrid anode of an ohmic contact anode and a Schottky contact anode, wherein the ohmic contact anode is located on a polarization-doped AlGaN cap layer, which can effectively utilize the holes in the cap layer and reduce the on-resistance; the Schottky contact anode contacts the semiconductor stack structure and the polarization junction, extending to the surface of the ohmic contact anode, and the ohmic contact cathode contacts the semiconductor stack structure, which simplifies the electrode preparation process on the basis of reducing the on-resistance and the turn-on voltage.

[0007] The present invention adopts at least the following technical solutions:

[0008] A double-channel SBD device with a polarization junction and polarization doping structure, comprising: a substrate, a buffer layer and a first channel layer sequentially stacked on the substrate, a semiconductor stack structure located on the first channel layer, a polarization junction located on a surface of the semiconductor stack structure, an ohmic contact anode located on the surface of the polarization junction, a Schottky contact anode and an ohmic contact cathode located on the first channel layer and contacting two side surfaces of the semiconductor stack structure, the Schottky contact anode extending to the surface of the ohmic contact anode;

[0009] The semiconductor stacked structure comprises a first insertion layer, a first barrier layer, a second channel layer, a second insertion layer, and a second barrier layer sequentially stacked on a first channel layer, wherein the second barrier layer is a polarization-doped AlGaN layer, and the Al component of the polarization-doped AlGaN layer gradually increases to x in a direction from the substrate to the channel layer, where 0.3≤x≤0.6;

[0010] The polarization junction is composed of a polarized GaN layer and a p-type polarized doped AlGaN cap layer stacked in sequence, and the Al component of the AlGaN cap layer gradually decreases from y in the direction from the substrate to the channel layer, wherein 0.3≤y≤0.6.

[0011] Furthermore, the polarized GaN layer is an i-type GaN layer, and its thickness is selected from 20 nm to 60 nm; preferably, its thickness is selected from 20 nm to 30 nm.

[0012] Furthermore, along the direction from the substrate to the channel layer, the Al composition of the AlGaN cap layer gradually decreases from 0.3 to 0.

[0013] Furthermore, the thickness of the polarization-doped AlGaN layer is 20 nm to 30 nm, and the Al composition of the polarization-doped AlGaN layer gradually increases from 0 to 0.3 in the direction from the substrate to the channel layer.

[0014] Furthermore, the thickness of the AlGaN cap layer is selected to be 30 nm to 100 nm.

[0015] Furthermore, the first barrier layer is an AlGaN barrier layer with a thickness of 20nm to 30nm and an Al composition of 0.27; the first channel layer is an i-type GaN layer with a thickness of 50nm to 100nm; and the first insertion layer is an AlN insertion layer with a thickness of 1nm.

[0016] Furthermore, the second channel layer is an i-type GaN layer with a thickness of 50 nm to 100 nm; the second insertion layer is an AlN insertion layer with a thickness of 1 nm.

[0017] Furthermore, a passivation layer is provided on the surface of the polarization-doped AlGaN layer, and the passivation layer extends to the surface of the polarization junction.

[0018] A method for preparing a double-channel SBD device with a polarization junction and polarization doping structure comprises the following steps:

[0019] Epitaxially growing a buffer layer, a first channel layer, a first insertion layer, a first barrier layer, a second channel layer, a second insertion layer, a second barrier layer, a polarized GaN layer, and a p-type polarized doped AlGaN cap layer on a substrate in sequence to form an epitaxial stack, wherein the second barrier layer is a polarized doped AlGaN layer, an Al composition of the polarized doped AlGaN layer gradually increases to x along a direction from the substrate to the channel layer, wherein 0.3≤x≤0.6, and an Al composition of the cap layer gradually decreases from y along a direction from the substrate to the channel layer, wherein 0.3≤y≤0.6;

[0020] Etching the epitaxial stack to a surface of the first channel layer to form a first opening and a second opening;

[0021] Etching the p-type polarization-doped AlGaN cap layer to the surface of the second barrier layer to form a third opening, wherein the third opening is close to the second opening;

[0022] forming an ohmic contact cathode in the second opening;

[0023] forming an ohmic contact anode on the cap layer near the first opening;

[0024] forming a Schottky contact anode in the first opening;

[0025] A passivation layer is formed between the anode and the cathode.

[0026] Furthermore, the polarized GaN layer is an i-type GaN layer, and its thickness is selected to be 20 nm to 60 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. 1 is a schematic cross-sectional view of an SBD device structure according to an embodiment of the present invention.

[0028] Figure 2 The figure shows the hole distribution in the P-type polarization-doped AlGaN cap layer in the polarization junction of the SBD device according to one embodiment of the present invention.

[0029] Figure 3 FIG. 4 is a forward characteristic diagram of an SBD device according to an embodiment of the present invention.

[0030] Figure 4 This is a breakdown voltage diagram of a double-channel SBD device with a polarized junction and polarized doping structure according to an example of the present invention. DETAILED DESCRIPTION

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention. The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0032] Spatially relative terms such as "below," "beneath," "below," "above," "upper," etc. are used in this specification to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.

[0033] In addition, the use of terms such as "first," "second," and the like to describe various elements, layers, regions, sections, and the like is not intended to be limiting. The use of "having," "containing," "including," and "comprising" are open-ended terms that indicate the presence of stated elements or features, but do not exclude additional elements or features, unless the context clearly indicates otherwise.

[0034] In order to make the above-mentioned beneficial effects and features of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] like Figure 1 As shown, the double-channel SBD device in this embodiment includes: a substrate 1, a buffer layer 2, a first channel layer 3, a semiconductor stacked structure, a polarization junction, an ohmic contact anode 10, a Schottky contact anode 9, an ohmic contact cathode 14 and a passivation layer 13.

[0036] The substrate 1 is selected from one of SiC, Si, sapphire, and diamond. In this embodiment, a low-cost, high-quality sapphire substrate is selected as the substrate 1. The buffer layer 2 and the first channel layer 3 are sequentially stacked on the substrate 1. The buffer layer 2 is preferably a high-resistance GaN layer with a thickness of 1 to 5 μm. In this embodiment, the buffer layer 2 is preferably a GaN buffer layer with a thickness of 3 μm, and the first channel layer 3 is preferably an i-type GaN channel layer with a thickness of 50 nm to 100 nm. In this embodiment, the channel layer thickness is 75 nm.

[0037] The semiconductor stacked structure consists of a first insertion layer 4, a first barrier layer 5, a second channel layer 6, a second insertion layer 7, and a second barrier layer 8 stacked in sequence. The first insertion layer 4 is an AlN insertion layer, and the first barrier layer 5 is an AlGaN barrier layer, preferably with a thickness of 25 nm and an Al composition of 0.27. Due to the self-polarization effect, the AlGaN barrier layer 5 and the GaN channel layer 3 form a high electron mobility and high concentration 2DEG at the AlGaN / GaN heterojunction. The AlN insertion layer 4 can form a deeper and narrower triangular potential well on the AlGaN / GaN surface, further improving the channel electron density, while suppressing the leakage of 2DEG into the AlGaN barrier layer, reducing the leakage current, and slowing down the current collapse phenomenon.

[0038] The second channel layer 6 is preferably an i-GaN channel layer with a thickness of 50nm to 100nm. In this embodiment, the thickness of the channel layer is 75nm. The second insertion layer 7 is preferably an AlN insertion layer, and its thickness is preferably 1nm. The second barrier layer 8 is a polarization-doped AlGaN layer with a thickness of 25nm; its Al component gradually increases in the direction from the substrate to the channel layer side. In this embodiment, the Al component of the polarization-doped AlGaN layer gradually increases from 0 to 0.3 in the direction from the substrate to the channel layer. The second conductive channel of the present invention uses a polarization-doped AlGaN barrier layer to increase the connectivity between the two channels, increase the ability of electrons to cross the second conductive channel from the first conductive channel, and have the effect of reducing the turn-on voltage.

[0039] The polarization junction is located on the surface of the semiconductor stacked structure, and the polarization junction is composed of a stacked polarized GaN layer 12 and a p-type polarized doped AlGaN cap layer 11. In this embodiment, the polarized GaN layer 12 is an i-type GaN layer, and its thickness is preferably 25 nm, the same as the thickness of the polarized doped AlGaN layer. Utilizing the polarization principle, the Al component of the polarized doped AlGaN cap layer 11 is gradually reduced in the direction from the substrate to the channel layer, generating a high concentration of holes. Without intentional doping, the polarized doped AlGaN cap layer has the characteristics of a P-type semiconductor, which can effectively replace the traditional P-type GaN cap layer and solve the problem of difficulty in preparing a high hole concentration P-type GaN cap layer. At the same time, the holes generated by polarization doping are not affected by temperature, so that the device has better thermal stability. In this embodiment, the thickness of the polarized doped AlGaN cap layer is 50 nm, and its Al component gradually decreases from 0.3 to 0 in the direction from the substrate to the channel layer. The setting of this polarization junction greatly solves the electric field concentration phenomenon and increases the breakdown voltage to 2.2 kV. At the same time, the i-type GaN layer 12 and the P-type polarization doped cap layer 11 in the polarization junction structure form a simple PN junction diode, which adds an additional conductive channel and reduces the on-resistance.

[0040] An ohmic contact anode 10 is disposed on the surface of the polarization junction. A Schottky contact anode 9 and an ohmic contact cathode 14 are respectively disposed on the surface of the first channel layer 3. The Schottky contact anode 9 contacts one side of the semiconductor stack structure and one side of the polarization junction located on the semiconductor stack structure, while the ohmic contact cathode 14 contacts the other side of the semiconductor stack structure. This allows the ohmic contact cathode 14 to directly contact the channel layer, which helps reduce resistance. The Schottky contact anode 9 extends to the surface of the ohmic contact anode 10. The ohmic contact anode 10 contacts the p-type polarization-doped AlGaN cap layer 11, enabling hole transport within the p-type polarization-doped AlGaN cap layer 11. The ohmic contact anode 10 is preferably a NiO / Au alloy, ITO / Au, or a Ti / Al / Ti / TiN alloy. The Schottky contact anode 9 is preferably a Ni / Au alloy. The ohmic contact cathode 14 is preferably a Ti / Al / Ni / Au alloy, a Ti / Al / Mo / Au alloy, or a Ti / Al / Ti / TiN alloy.

[0041] The work function of the p-type polarization-doped AlGaN layer is greater than that of all known metal semiconductors. The Schottky contact metal, a p-type barrier layer, cannot effectively utilize the holes in the polarization-doped AlGaN cap layer. The ohmic contact metal effectively utilizes the holes in the cap layer, reducing on-resistance. The Schottky contact anode 9 forms a Schottky barrier in contact with the first and second channel layers, extending to the surface of the ohmic contact electrode 10. This simplifies the electrode fabrication process and does not affect the operation of the electrode 10.

[0042] In order to make the dual-channel SBD device structure of the present invention clearer, the device structure of the present invention is further described below in conjunction with the preparation method.

[0043] First, a sapphire substrate was selected and an MOCVD process was used to sequentially epitaxially grow a high-resistance GaN buffer layer, a first channel layer, a first insertion layer, a first barrier layer, a second channel layer, a second insertion layer, a second barrier layer, a polarization GaN layer, and a p-type polarization-doped AlGaN cap layer on the sapphire substrate to form an epitaxial stack. The high-resistance GaN buffer layer was 3 μm thick, the first channel layer was a GaN channel layer with a thickness of 75 nm, the first insertion layer was an AlN insertion layer with a thickness of 1 nm, the first barrier layer was an AlGaN barrier layer with a thickness of 25 nm and an Al composition of 0.27, the second channel layer was a GaN channel layer with a thickness of 75 nm, and the second insertion layer was preferably an AlN insertion layer with a thickness of 1 nm. The second barrier layer was a polarization-doped AlGaN barrier layer with a thickness of 25 nm, and the Al composition gradually increased from 0 to 0.3 along the direction from the substrate to the channel layer. The polarization-doped AlGaN barrier layer increases the connectivity between the two channels, increases the ability of electrons to cross from the first conductive channel to the second conductive channel, and reduces the turn-on voltage.

[0044] The thickness of the polarized GaN layer is 25nm, equal to the thickness of the p-type polarized AlGaN barrier layer. The thickness of the p-type polarized AlGaN cap layer is 50nm, and its Al composition gradually decreases from 0.3 to 0 along the direction from the substrate to the channel layer.

[0045] The epitaxial stack is then etched to the surface of the first channel layer to form a first opening and a second opening. The p-type polarization-doped AlGaN cap layer is then etched to the surface of the second barrier layer to form a third opening, which is adjacent to the second opening.

[0046] An ohmic contact cathode is formed in the second opening, and the ohmic contact cathode contacts the first channel layer, the first insertion layer, the first barrier layer, the second channel layer, the second insertion layer and the second barrier layer. The ohmic contact cathode is made of Ti / Al / Ni / Au alloy, Ti / Al / Mo / Au alloy or Ti / Al / Ti / TiN alloy.

[0047] An ohmic contact anode is formed on the surface of the p-type polarization doped AlGaN cap layer, on a side close to the first opening. The ohmic contact anode is made of NiO / Au alloy, ITO / Au or Ti / Al / Ti / TiN alloy.

[0048] A Schottky contact anode is formed in the first opening and on the surface of the ohmic contact anode. The Schottky contact anode contacts the first channel layer, the first insertion layer, the first barrier layer, the second channel layer, the second insertion layer and the second barrier layer. The Schottky contact anode is made of Ni / Au alloy.

[0049] A passivation layer 13 is deposited between the Schottky contact anode 9 and the ohmic contact cathode 14 to prevent air breakdown of the device and improve the withstand voltage characteristics of the device. The passivation layer 13 is preferably made of Si3N4.

[0050] Figure 2 Figure 1 shows the hole distribution in the P-type polarization-doped AlGaN cap layer in the polarization junction of a double-channel SBD device according to an embodiment of the present invention. 18 cm -3 , indicating that the polarization-doped cap layer can effectively replace the P-type GaN cap layer.

[0051] Figure 3 This is a forward characteristic diagram of a dual-channel SBD device with a polarized junction and polarized doping structure according to an embodiment of the present invention. Its turn-on voltage is 0.67V and its on-resistance is 3.13mΩ·cm. 2 , indicating that the use of dual-channel and polarization-doped AlGaN barrier layers reduces the turn-on voltage and on-resistance of the device.

[0052] Figure 4This is a breakdown voltage diagram of a double-channel SBD device with a polarized junction and polarized doping structure according to an embodiment of the present invention. The breakdown voltage reaches 2.2 kV, proving that the polarized junction structure greatly enhances the breakdown voltage of the device.

[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A double-channel SBD device with a polarization junction and polarization doping structure, characterized in that: The invention comprises a substrate, a buffer layer and a first channel layer sequentially stacked on the substrate, a semiconductor stack structure located on the first channel layer, a polarization junction located on the surface of the semiconductor stack structure, an ohmic contact anode located on the surface of the polarization junction, a Schottky contact anode and an ohmic contact cathode located on the first channel layer and contacting two side surfaces of the semiconductor stack structure, wherein the Schottky contact anode extends to the surface of the ohmic contact anode; The semiconductor stacked structure comprises a first insertion layer, a first barrier layer, a second channel layer, a second insertion layer, and a second barrier layer sequentially stacked on a first channel layer, wherein the second barrier layer is a polarization-doped AlGaN layer, and the Al component of the polarization-doped AlGaN layer gradually increases to x in a direction from the substrate to the channel layer, where 0.3≤x≤0.6; The polarization junction is composed of a polarized GaN layer and a p-type polarized doped AlGaN cap layer stacked in sequence, and the Al component of the AlGaN cap layer gradually decreases from y in the direction from the substrate to the channel layer, wherein 0.3≤y≤0.

6.

2. The dual-channel SBD device according to claim 1, characterized in that: The polarized GaN layer is an i-type GaN layer, and its thickness is selected to be 20nm to 60nm.

3. The dual-channel SBD device according to claim 2, characterized in that: The thickness of the polarized GaN layer is 20 nm to 30 nm.

4. The dual-channel SBD device according to any one of claims 1 to 3, characterized in that: Along the direction from the substrate to the channel layer, the Al composition of the AlGaN cap layer gradually decreases from 0.3 to 0.

5. The dual-channel SBD device according to claim 4, characterized in that: The thickness of the polarization doped AlGaN layer is 20 nm to 30 nm, and the Al composition of the polarization doped AlGaN layer gradually increases from 0 to 0.3 in the direction from the substrate to the channel layer.

6. The dual-channel SBD device according to claim 1, 2, 3 or 5, characterized in that: The thickness of the AlGaN cap layer is selected to be 30nm to 100nm.

7. The dual-channel SBD device according to claim 6, characterized in that: The first barrier layer is an AlGaN barrier layer with a thickness of 20nm to 30nm and an Al composition of 0.27; the first channel layer is an i-type GaN layer with a thickness of 50nm to 100nm; the first insertion layer is an AlN insertion layer with a thickness of 1nm.

8. The dual-channel SBD device according to claim 6, characterized in that: The second channel layer is an i-type GaN layer with a thickness of 50 nm to 100 nm; the second insertion layer is an AlN insertion layer with a thickness of 1 nm.

9. The dual-channel SBD device according to claim 7 or 8, characterized in that: A passivation layer is further provided on the surface of the polarization-doped AlGaN layer, and the passivation layer extends to the surface of the polarization junction.

10. A method for preparing a double-channel SBD device with a polarization junction and polarization doping structure, characterized in that: The following steps are involved: Epitaxially growing a buffer layer, a first channel layer, a first insertion layer, a first barrier layer, a second channel layer, a second insertion layer, a second barrier layer, a polarized GaN layer, and a p-type polarized doped AlGaN cap layer on a substrate in sequence to form an epitaxial stack, wherein the second barrier layer is a polarized doped AlGaN layer, an Al composition of the polarized doped AlGaN layer gradually increases to x along a direction from the substrate to the channel layer, wherein 0.3≤x≤0.6, and an Al composition of the cap layer gradually decreases from y along a direction from the substrate to the channel layer, wherein 0.3≤y≤0.6; Etching the epitaxial stack to a surface of the first channel layer to form a first opening and a second opening; Etching the p-type polarization-doped AlGaN cap layer to the surface of the second barrier layer to form a third opening, wherein the third opening is close to the second opening; forming an ohmic contact cathode in the second opening; forming an ohmic contact anode on the cap layer near the first opening; forming a Schottky contact anode in the first opening; A passivation layer is formed between the anode and the cathode.

11. The preparation method according to claim 10, characterized in that: The polarized GaN layer is an i-type GaN layer, and its thickness is selected to be 20nm to 60nm.

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