A GaN multi-channel structure without channel coupling effect and GaN HEMT device

Abstract

The present invention relates to the field of semiconductor material technology, and specifically to a GaN multi-channel structure without channel coupling effect. The structure includes a plurality of GaN channel layers and AlGaN barrier layers that alternate from bottom to top, wherein the GaN channel layer and the AlGaN barrier layer form a GaN / AlGaN heterojunction, and a channel isolation layer is provided between two adjacent GaN / AlGaN heterojunctions. The present invention provides a channel isolation layer between the GaN / AlGaN heterojunctions so that the electrons in each channel no longer affect each other, and the multi-channel current can increase exponentially with the number of channels, thereby eliminating the coupling effect between channels, and will not introduce impurity scattering effect, and the electron mobility of 2DEG will not be affected.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and in particular to a GaN multi-channel structure without channel coupling effect and a GaN HEMT device. Background Art

[0002] The existing multi-channel GaN HEMT structure has a coupling effect between channels, which leads to a decrease in the electron concentration of each channel. Although the output current of the device is finally improved, it is not a doubling relationship. Therefore, how to solve the coupling effect between multiple channels is of great significance. Summary of the invention

[0003] Based on the above description, the present invention provides a GaN multi-channel structure without channel coupling effect, and eliminates the coupling effect between channels by arranging a channel isolation layer between GaN / AlGaN heterojunctions.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] A GaN multi-channel structure without channel coupling effect comprises a plurality of GaN channel layers and AlGaN barrier layers alternately arranged from bottom to top, wherein the GaN channel layers and the AlGaN barrier layers form GaN / AlGaN heterojunctions, and a channel isolation layer is provided between two adjacent GaN / AlGaN heterojunctions.

[0006] As a preferred implementation, the material of the trench isolation layer is a medium with no polarization property. Preferably, the material of the trench isolation layer is air, Ga2O3, Al2O3, In2O3.

[0007] As a preferred implementation, the structure further includes a substrate and a buffer layer, and the plurality of alternating GaN channel layers and AlGaN barrier layers are fabricated on the buffer layer.

[0008] As a preferred implementation, a channel isolation layer is formed between the buffer layer and the bottom GaN channel layer.

[0009] Preferably, the material of the substrate is GaN, Si, AlN, SiC, Al2O3, and the buffer layer is GaN doped with C or Fe elements.

[0010] As a preferred embodiment, the structure further includes a source, a gate and a drain. The source and the drain are respectively fabricated on both sides of the GaN / AlGaN heterojunction and electrically connected thereto, and the gate is located between the source and the drain.

[0011] The present invention also provides a method for preparing the above-mentioned GaN multi-channel structure, wherein the GaN channel layer and the AlGaN barrier layer are produced by epitaxial growth, and the channel isolation layer is produced by oxidation of an InAlN sacrificial layer or oxidation and corrosion of an InAlN sacrificial layer or oxidation, corrosion and deposition of a medium of an InAlN sacrificial layer.

[0012] The present invention also provides a GaN HEMT device, comprising the above-mentioned GaN multi-channel structure.

[0013] Compared with the prior art, the main advantage of the technical solution of the present application is that by setting a channel isolation layer between the GaN / AlGaN heterojunction, the electrons in each channel no longer affect each other, and the multi-channel current can increase exponentially with the number of channels, thereby eliminating the coupling effect between channels, and will not introduce impurity scattering effects, and the electron mobility of 2DEG will not be affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A GaN multi-channel structure provided in Example 1 of the present invention, wherein A is a three-dimensional diagram and B is a schematic diagram of a longitudinal cross-sectional structure at the channel;

[0015] Figure 2 A GaN multi-channel structure provided by Embodiment 2 of the present invention;

[0016] Figure 3 A process flow chart of a GaN multi-channel structure provided in Example 1 of the present invention; in the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0017] 1 substrate, 2 buffer layer, 3 channel isolation layer, 4 GaN channel layer, 5 AlGaN barrier layer. DETAILED DESCRIPTION

[0018] The common method to reduce the channel coupling effect is to perform n-type doping on the AlGaN barrier layer to supplement electrons and offset the influence of the channel coupling effect on the device current. Although this method can offset the influence of the channel coupling effect through electron doping compensation, doping will bring about impurity scattering effect and reduce the electron mobility of 2DEG.

[0019] Based on this, the present invention provides a new GaN multi-channel structure, which eliminates the coupling effect between channels by making an isolation layer between heterojunction channels, so that the channel current is not negatively affected by the coupling effect, and does not bring about impurity scattering effect, which is easy to implement. The specific scheme is as follows:

[0020] A GaN multi-channel structure without channel coupling effect, comprising a plurality of GaN layers 4 and AlGaN barrier layers 5 alternately arranged from bottom to top, wherein the GaN channel layer 4 and the AlGaN barrier layer 5 form a GaN / AlGaN heterojunction, and the improvement of the invention is that a channel isolation layer is provided between two adjacent GaN / AlGaN heterojunctions. That is, the GaN channel layer 4 and the AlGaN barrier layer 5 form a combination, and a channel isolation layer 3 is provided between two adjacent combinations.

[0021] By setting a channel isolation layer 3 between the GaN / AlGaN heterojunction, the electrons in each channel no longer affect each other, and the multi-channel current can increase exponentially with the number of channels, thereby eliminating the coupling effect between channels, and will not introduce impurity scattering effects, and the electron mobility of 2DEG will not be affected.

[0022] The material of the channel isolation layer 3 is preferably a medium with no polarization characteristics, such as air, Ga2O3, Al2O3, In2O3. The thickness of the GaN channel layer 4 is preferably 2-100 nm, and the thickness of the AlGaN barrier layer 5 is preferably 8-30 nm.

[0023] It can be understood that the multi-channel structure further includes a substrate 1 and a buffer layer 2, and a plurality of GaN channel layers 4 and AlGaN barrier layers 5 are fabricated on the buffer layer in an alternating manner.

[0024] Preferably, the thickness of the substrate is 375-1000 μm, the thickness of the buffer layer is 500-2200 nm. The material of the substrate is GaN, Si, AlN, SiC, Al2O3, and the buffer layer is GaN doped with C or Fe elements.

[0025] A channel isolation layer 3 is also formed between the buffer layer 2 and the bottom GaN channel layer 4 .

[0026] It can also be understood that the structure also includes a source, a gate and a drain. The source and the drain are respectively made on both sides of the GaN / AlGaN heterojunction and are electrically connected thereto, and the gate is located between the source and the drain.

[0027] The above-mentioned GaN multi-channel structure without channel coupling effect can be prepared by the following method: the GaN channel layer 4 and the AlGaN barrier layer 5 are made by epitaxial growth, and the channel isolation layer 3 is made by oxidation of the InAlN sacrificial layer or oxidation and corrosion of the InAlN sacrificial layer or oxidation, corrosion and deposition of the medium of the InAlN sacrificial layer.

[0028] The present invention also provides a GaN HEMT device, comprising the above-mentioned GaN multi-channel structure.

[0029] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0030] Example 1

[0031] This embodiment provides a GaN multi-channel structure without channel coupling effect. Figure 1 , from bottom to top, it includes a plurality of alternating GaN layers 4 and AlGaN barrier layers 5, wherein the GaN channel layer 4 and the AlGaN barrier layer 5 form a GaN / AlGaN heterojunction, and a channel isolation layer 3 is provided between two adjacent GaN / AlGaN heterojunctions, wherein the channel isolation layer is InAlO formed by oxidation of InAlN, and the preparation method thereof is as follows:

[0032] Step 1, epitaxial substrate preparation: The substrate uses a high-resistance substrate, and the substrate material can be GaN, Si, SiC, Al2O3, etc., with a thickness of 375 to 1000μm. Then, grow an Fe or C-doped GaN buffer layer with a thickness of 500 to 2200nm, an unintentionally doped InAlN decoupling sacrificial layer with a thickness of 10 to 300nm, an unintentionally doped GaN channel layer with a thickness of 20 to 100nm, and an unintentionally doped AlGaN barrier layer with a thickness of 8 to 30nm by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). The specific composition of InAlN is In x Al 1-x N, 0.15<x≤0.3, in this embodiment, x=0.17. AlGaN / GaN / InAlN structure can be arranged periodically according to actual needs to form any number of channels. For the convenience of demonstration, a double channel structure will be used for demonstration later.

[0033] Step 2, etching mask deposition and patterning: first, apply photoresist on the wafer, then photolithography and development will expose the area to be etched, complete the definition of the etching pattern, and the strip channel width protected by the etching mask is 30 to 300nm. Optionally, this etching mask layer can also be a medium such as Si3N4, SiO2, Al2O3, or a composite medium formed by a combination of them. If such a dielectric mask is used, it is necessary to use deep reactive ion etching (DRIE) or inductively coupled plasma etching (ICP) after photolithography to transfer the pattern on the photoresist to the dielectric mask, and then remove the photoresist layer.

[0034] Step 3, nano-channel etching and etching mask removal: The masked substrate is etched into a deep trench structure using deep reactive ion etching (DRIE) or inductively coupled plasma etching (ICP) in Cl2 plasma. The deep trench etching depth needs to reach the GaN buffer layer. After the etching is completed, the etching mask layer is removed by wet method.

[0035] Step 4, oxidation of sacrificial layer: using wet oxidation process, oxidize InAlN at 900℃, with water vapor as reaction gas and N2 as carrier gas. Because the Al component in InAlN is relatively high, the higher the Al component, the faster the oxidation rate. By controlling the wet oxidation time, it is possible to complete the oxidation of InAlN while ensuring that only part of the AlGaN and GaN layers are oxidized, thus retaining the nanochannel. At the same time, the InAlO produced after oxidation no longer has a polarization effect, and can be used as an isolation medium to isolate the channel from the channel, thereby removing the channel coupling.

[0036] Example 2

[0037] This embodiment provides a GaN multi-channel structure without channel coupling effect. Figure 2 , including a plurality of alternating GaN layers 4 and AlGaN barrier layers 5 from bottom to top, wherein the GaN channel layer 4 and the AlGaN barrier layer 5 form a GaN / AlGaN heterojunction, and a channel isolation layer 3 is provided between two adjacent GaN / AlGaN heterojunctions, wherein the channel isolation layer is air. The preparation method thereof is different from that of Example 1 in that after the oxidation of the sacrificial layer in step 4 is completed, the oxide layer is etched by a wet method to release the nanochannel, thereby forming a multi-channel structure with an air isolation layer.

[0038] Example 3

[0039] The present embodiment provides a GaN multi-channel structure without channel coupling effect, comprising a plurality of alternating GaN layers 4 and AlGaN barrier layers 5 from bottom to top, wherein the GaN channel layer 4 and the AlGaN barrier layer 5 form a GaN / AlGaN heterojunction, and a channel isolation layer 3 is provided between two adjacent GaN / AlGaN heterojunctions, wherein the channel isolation layer is Al2O3. The preparation method thereof is different from that of Example 1 in that after the oxidation of the sacrificial layer in step 4 is completed, the oxide layer is etched by a wet method to release the nanochannels to form a multi-channel structure with an air isolation layer, and then Al2O3 is deposited under the action of a mask.

[0040] It should be noted that in the description of the present application, the description of the drawings and embodiments is illustrative rather than restrictive, and the same drawings throughout the embodiments of the specification mark the same structure. In addition, for the sake of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. In addition, "on" refers to positioning an element on or below another element, but does not essentially mean positioning on the upper side of another element according to the direction of gravity. The terms "upper", "lower", "top", "bottom", "inside", "outside", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a GaN multi-channel structure without channel coupling effect, characterized in that: From bottom to top, it includes a plurality of GaN channel layers and AlGaN barrier layers that are alternately arranged in sequence, wherein the GaN channel layers and the AlGaN barrier layers form a GaN / AlGaN heterojunction, and a channel isolation layer is provided between two adjacent GaN / AlGaN heterojunctions; The GaN channel layer and the AlGaN barrier layer are manufactured by epitaxial growth, and the channel isolation layer is manufactured by oxidation of an InAlN sacrificial layer, oxidation and corrosion of an InAlN sacrificial layer, or oxidation, corrosion and deposition of a dielectric by an InAlN sacrificial layer.

2. The method for preparing a GaN multi-channel structure without channel coupling effect according to claim 1, characterized in that: The material of the channel isolation layer is a medium with no polarization property.

3. The method for preparing a GaN multi-channel structure without channel coupling effect according to claim 1, characterized in that: The material of the channel isolation layer is air, Ga2O3, Al2O3, or In2O3.

4. The method for preparing a GaN multi-channel structure without channel coupling effect according to any one of claims 1 to 3, characterized in that: The invention also comprises a substrate and a buffer layer, wherein the plurality of GaN channel layers and AlGaN barrier layers which are alternately formed in sequence are formed on the buffer layer.

5. The method for preparing a GaN multi-channel structure without channel coupling effect according to claim 4, characterized in that: A channel isolation layer is formed between the buffer layer and the bottom GaN channel layer.

6. The method for preparing a GaN multi-channel structure without channel coupling effect according to claim 4, characterized in that: The material of the substrate is GaN, Si, AlN, SiC, Al2O3, and the buffer layer is GaN doped with C or Fe elements.

7. The method for preparing a GaN multi-channel structure without channel coupling effect according to any one of claims 1 to 3, characterized in that: It also includes a source electrode, a gate electrode and a drain electrode. The source electrode and the drain electrode are respectively made on both sides of the GaN / AlGaN heterojunction and are electrically connected thereto. The gate electrode is located between the source electrode and the drain electrode.

Images