阅读说明：本技术 压致势垒变化式氮化镓压力传感器及其制备方法 (Pressure-induced barrier variation type gallium nitride pressure sensor and preparation method thereof ) 是由 刘泽文 孙剑文 于 2021-08-20 设计创作，主要内容包括：本发明公开了压致势垒变化式氮化镓压力传感器及其制备方法。该压致势垒变化式氮化镓压力传感器包括：第一衬底和外延结构,外延结构包括依次形成在第一衬底上的GaN缓冲层、GaN沟道层、AlN插入层、AlGaN势垒层、GaN帽层；其中,AlGaN势垒层具有第一凹槽,第一凹槽内形成有欧姆接触层,欧姆接触层与AlN插入层和GaN沟道层界面处的二维电子气连通形成下电极；GaN帽层的至少部分上表面形成有上电极；以及钝化层,钝化层覆盖外延结构的至少部分上表面。该压致势垒变化式氮化镓压力传感器可以在无外接驱动电压的情况下,直接根据上电极、下电极间电势差测量得到外部压力的变化,即在无外接驱动电压下实现对外部压力变化的零功耗检测。(The invention discloses a pressure-induced barrier variation type gallium nitride pressure sensor and a preparation method thereof. The pressure induced barrier variable gallium nitride pressure sensor comprises: the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate; the AlGaN barrier layer is provided with a first groove, an ohmic contact layer is formed in the first groove, and the ohmic contact layer is communicated with two-dimensional electron gas at the interface of the AlN insert layer and the GaN channel layer to form a lower electrode; an upper electrode is formed on at least part of the upper surface of the GaN cap layer; and a passivation layer covering at least a portion of the upper surface of the epitaxial structure. The pressure-induced potential barrier variable gallium nitride pressure sensor can directly measure the change of external pressure according to the potential difference between the upper electrode and the lower electrode under the condition of no external driving voltage, namely, the zero-power consumption detection of the change of the external pressure is realized under the condition of no external driving voltage.)

1. A piezoelectric barrier variable gallium nitride pressure sensor, comprising:

the GaN-based epitaxial structure comprises a first substrate and an epitaxial structure, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate; the AlGaN barrier layer is provided with a first groove, an ohmic contact layer is formed in the first groove, and the ohmic contact layer is communicated with two-dimensional electrons at the interface of the AlN insert layer and the GaN channel layer to form a lower electrode; an upper electrode is formed on at least part of the upper surface of the GaN cap layer;

a passivation layer covering at least a portion of an upper surface of the epitaxial structure.

2. The piezobarrier-changing gallium nitride pressure sensor according to claim 1, wherein the material of the first substrate is Si, SiC, GaN or sapphire.

3. The piezobarrier-changing gallium nitride pressure sensor according to claim 1, wherein the thickness of the GaN buffer layer is 0.5 to 10 μm;

optionally, the thickness of the GaN channel layer is 0.2-10 mu m;

optionally, the AlN insert layer has a thickness of 0.5 to 3 nm;

optionally, the thickness of the AlGaN barrier layer is 10-1000 nm, and the depth of the first groove is 10-1000 nm;

optionally, the thickness of the GaN cap layer is 0-10 nm.

4. The pressure-induced barrier variable gallium nitride pressure sensor according to claim 1, wherein the material of the upper electrode is at least one selected from Ti, Cr, Ni, Pt, and Au.

5. The piezobarrier-changing gallium nitride pressure sensor according to claim 1, wherein the material of the passivation layer is an inorganic material;

optionally, the inorganic material is selected from at least one of silicon oxide, silicon nitride and aluminum oxide;

optionally, the thickness of the passivation layer is 50-600 nm;

optionally, the passivation layer is made of a low stress material, and the stress range of the low stress material is 0-300 MPa.

6. The piezobarrier-changing gallium nitride pressure sensor according to claim 1, wherein the passivation layer has an electrode hole and an external electrode, and the external electrode is connected to the upper electrode and the lower electrode through the electrode hole.

7. The piezobarrier-change gallium nitride pressure sensor according to any one of claims 1 to 6, wherein the first substrate has a second groove on a surface of a side thereof away from the epitaxial structure, and the piezobarrier-change gallium nitride pressure sensor further comprises: a bonding layer, a second substrate and a reference pressure chamber;

the bonding layer is formed on one side surface of the first substrate far away from the epitaxial structure, the second substrate is bonded with the first substrate through the bonding layer, and the reference pressure cavity is formed by the second substrate and the second groove;

optionally, the depth of the second groove is 50-400 μm;

optionally, a projected area of the second groove on the first substrate is larger or smaller than a projected area of the upper electrode on the first substrate.

8. A method for preparing the pressure-induced barrier variable gallium nitride pressure sensor according to any one of claims 1 to 7, comprising:

(1) forming an epitaxial structure on a first substrate, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate;

(2) selectively etching the epitaxial structure to form an epitaxial table top;

(3) selectively etching the AlGaN barrier layer to form the first groove, and preparing an ohmic contact layer communicated with two-dimensional electron gas in the first groove to form a lower electrode;

(4) forming an upper electrode on at least part of the upper surface of the GaN cap layer;

(5) and forming a passivation layer on at least part of the upper surface of the epitaxial structure to obtain the piezobarrier-variable gallium nitride pressure sensor.

9. The method of claim 8, further comprising: and forming an electrode hole on the passivation layer, and forming external electrodes respectively connected with the upper electrode and the lower electrode through the electrode hole.

10. The method of claim 8, further comprising: selectively etching at least part of the surface of one side of the first substrate, which is far away from the epitaxial structure, to form a second groove; and bonding a second substrate on the surface of one side of the first substrate, which is far away from the epitaxial structure, so that the second substrate and the second groove form a reference pressure cavity.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a pressure-induced barrier variation type gallium nitride pressure sensor and a preparation method thereof.

Background

The pressure sensor is a transducer which converts pressure signals into directly acquired electrical signals and is widely applied to the fields of industry, aerospace, new energy, rail transit, automotive electronics and the like. The traditional silicon-based piezoresistive pressure sensor adopts a diffusion process to form a piezoresistor, the resistance value of the piezoresistor changes along with the change of external pressure, but the temperature drift of the silicon-based piezoresistive pressure sensor is serious, and the silicon-based piezoresistive pressure sensor can only work in an environment with the temperature lower than 120 ℃.

The forbidden band width of the GaN material is 3.4eV, the GaN material is a good high-temperature resistant material, and the pressure sensor of the GaN material can be applied to a working environment of 600 ℃. The GaN material is a piezoelectric material, and by utilizing the piezoelectric property of the GaN material, if metal electrodes are manufactured on the upper surface and the lower surface of the pressure material, although output signals of the upper electrode and the lower electrode can change along with the pressure change, the thickness of the GaN material is generally larger, and the GaN material cannot be compatible with a microelectronic process. In addition, the AlGaN/GaN heterostructure forms a high concentration, high electron mobility, two-dimensional electron gas (2DEG) on the surface of the GaN channel layer. The AlGaN/GaN heterostructure is used as a pressure sensor, and usually, the concentration of two-dimensional electron gas is required to be changed along with the change of pressure under the action of external driving voltage, so that energy consumption is required. However, many application scenarios require very low or even zero power consumption pressure sensors.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide a piezobarrier-variable gallium nitride pressure sensor and a preparation method thereof. The pressure-induced potential barrier variable gallium nitride pressure sensor can directly measure the change of external pressure according to the potential difference between the upper electrode and the lower electrode under the condition of no external driving voltage, namely, the zero-power consumption detection of the change of the external pressure is realized under the condition of no external driving voltage. Meanwhile, the pressure-induced barrier changing type gallium nitride pressure sensor also has the advantages of high temperature resistance and the like.

In one aspect of the invention, a pressure induced barrier varying gallium nitride pressure sensor is presented. According to an embodiment of the present invention, the piezoelectric barrier varying gallium nitride pressure sensor includes: the GaN-based epitaxial structure comprises a first substrate and an epitaxial structure, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate; the AlGaN barrier layer is provided with a first groove, an ohmic contact layer is formed in the first groove, and the ohmic contact layer is communicated with two-dimensional electrons at the interface of the AlN insert layer and the GaN channel layer to form a lower electrode; an upper electrode is formed on at least part of the upper surface of the GaN cap layer; and a passivation layer covering at least a portion of an upper surface of the epitaxial structure.

In the piezobarrier-varying gallium nitride pressure sensor according to the above-described embodiment of the present invention, a high-concentration, high-electron-mobility two-dimensional electron gas (2DEG) is formed at the interface of the AlN insertion layer and the GaN channel layer due to piezoelectric polarization and self-polarization effects, the two-dimensional electron gas may serve as a lower electrode of the pressure sensor, the schottky contact metal layer on the upper surface of the AlGaN barrier layer serves as an upper electrode, and the change in external pressure is reflected by the potential difference between the upper and lower electrodes. On one hand, the polarization charges on the upper surface and the lower surface of the AlGaN barrier layer are changed by utilizing the piezoelectric property of the AlGaN material through the external pressure; on the other hand, the energy level in the quantum well is also bent by the external pressure, so that the charge density in the two-dimensional electron gas quantum well of the lower electrode is changed, the electric potential energy of the upper surface and the lower surface of the AlGaN barrier layer is changed, and the pressure induced barrier change effect is generated. Furthermore, the pressure signal is converted into voltage or potential to be output by measuring the electromotive potential difference of the upper electrode and the lower electrode, and the sensing and the detection of the pressure can be realized. In the pressure sensor, the two-dimensional electron gas at the interface of the AlN insert layer and the GaN channel layer is used as the lower electrode, so that the process difficulty of using a metal electrode as the lower electrode in the conventional process is avoided; in addition, the external pressure changes the energy level in the two-dimensional electron gas quantum well, so that the transportation of the two-dimensional electron gas is adjusted, the charge density of the lower electrode is changed, the potential difference between the upper electrode and the lower electrode is formed, energy consumption is not needed, and zero power consumption detection of external pressure change can be realized.

In addition, the piezobarrier-variable gallium nitride pressure sensor according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the present invention, the material of the first substrate is Si, SiC, GaN, or sapphire.

In some embodiments of the present invention, the GaN buffer layer has a thickness of 0.5-10 μm.

In some embodiments of the present invention, the GaN channel layer has a thickness of 0.2-10 μm.

In some embodiments of the present invention, the AlN insert layer has a thickness of 0.5 to 3 nm.

In some embodiments of the invention, the AlGaN barrier layer has a thickness of 10 to 1000nm, and the depth of the first groove is 10 to 1000 nm.

In some embodiments of the present invention, the GaN cap layer has a thickness of 0-10 nm.

In some embodiments of the present invention, the material of the upper electrode is selected from at least one of Ti, Cr, Ni, Pt, and Au.

In some embodiments of the present invention, the passivation layer is made of an inorganic material.

In some embodiments of the present invention, the inorganic material is selected from at least one of silicon oxide, silicon nitride, aluminum oxide.

In some embodiments of the present invention, the thickness of the passivation layer is 50 to 600 nm.

In some embodiments of the present invention, the passivation layer is made of a low stress material, and the stress range of the low stress material is 0 to 300 MPa.

In some embodiments of the present invention, the passivation layer has an electrode hole and an external electrode, and the external electrode is connected to the upper electrode and the lower electrode through the electrode hole.

In some embodiments of the present invention, a surface of the first substrate on a side away from the epitaxial structure has a second groove, and the piezobarrier-variable gallium nitride pressure sensor further includes: a bonding layer, a second substrate and a reference pressure chamber; the bonding layer is formed on one side surface of the first substrate far away from the epitaxial structure, and the second substrate is bonded with the first substrate through the bonding layer and forms the reference pressure cavity with the second groove.

In some embodiments of the present invention, the depth of the second groove is 50 to 400 μm.

In some embodiments of the present invention, a projected area of the second groove on the first substrate is larger or smaller than a projected area of the upper electrode on the first substrate.

In another aspect of the invention, the invention provides a method for preparing the piezoelectric barrier changing gallium nitride pressure sensor of the above embodiment. According to an embodiment of the invention, the method comprises: (1) forming an epitaxial structure on a first substrate, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate; (2) selectively etching the epitaxial structure to form an epitaxial table top; (3) selectively etching the AlGaN barrier layer to form the first groove, and preparing an ohmic contact layer communicated with two-dimensional electron gas in the first groove to form a lower electrode; (4) forming an upper electrode on at least part of the upper surface of the GaN cap layer; (5) and forming a passivation layer on at least part of the upper surface of the epitaxial structure to obtain the piezobarrier-variable gallium nitride pressure sensor. The pressure-induced potential barrier variable gallium nitride pressure sensor prepared by the method can directly measure the change of the external pressure according to the potential difference between the upper electrode and the lower electrode under the condition of no external driving voltage, namely, the zero power consumption detection of the change of the external pressure is realized under the condition of no external driving voltage.

In addition, the method for manufacturing the piezobarrier-variable gallium nitride pressure sensor according to the above embodiment of the invention may further have the following additional technical features:

in some embodiments of the invention, the method further comprises: and forming an electrode hole on the passivation layer, and forming external electrodes respectively connected with the upper electrode and the lower electrode through the electrode hole.

In some embodiments of the invention, the method further comprises: selectively etching at least part of the surface of one side of the first substrate, which is far away from the epitaxial structure, to form a second groove; and bonding a second substrate on the surface of one side of the first substrate, which is far away from the epitaxial structure, so that the second substrate and the second groove form a reference pressure cavity.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of the energy band of a piezobarrier-changing GaN pressure sensor;

fig. 2 is a schematic structural diagram of a piezobarrier-changing gallium nitride pressure sensor according to an embodiment of the present invention, wherein a is a schematic structural diagram of a top surface, and b is a schematic structural diagram of a cross-section of a-a' surface in a;

fig. 3 is a schematic structural diagram of a piezobarrier-changing gallium nitride pressure sensor according to an embodiment of the present invention, wherein a is a schematic structural diagram of a top surface, and b is a schematic structural diagram of a cross-section of a-a' surface in a;

fig. 4 is a schematic structural diagram of a piezobarrier-changing gallium nitride pressure sensor according to an embodiment of the present invention, wherein a is a schematic structural diagram of a top surface, and b is a schematic structural diagram of a cross-section of a-a' surface in a;

fig. 5 is a schematic structural diagram of a piezobarrier-changing gallium nitride pressure sensor according to an embodiment of the present invention, wherein a is a schematic structural diagram of a top surface, and b is a schematic structural diagram of a cross-section of a-a' surface in a.

Reference numerals:

1: upper electrode, 2: lower electrode, 3: AlGaN barrier layer, 4: AlN insertion layer, 5: passivation layer, 6: GaN channel layer, 7: GaN buffer layer, 8: first substrate, 9: bonding layer, 10: second substrate, 11: reference pressure chamber, 12: a GaN cap layer.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In one aspect of the invention, a pressure induced barrier varying gallium nitride pressure sensor is presented. The following further describes the piezobarrier-changing gallium nitride pressure sensor according to an embodiment of the present invention.

As shown in figure 1, due to spontaneous polarization and piezoelectric polarization effects of an AlGaN barrier layer and a GaN channel layer in the AlGaN/GaN heterostructure, two-dimensional electron gas with high concentration and high electron mobility is formed on the upper surface of the GaN channel layer, the pressure sensor adopts the two-dimensional electron gas (2DEG) as a lower electrode, and connects an ohmic contact layer to the two-dimensional electron gas (2DEG) through selective groove etching of the AlGaN layer, so that the problem that the lower electrode needs to use a metal process is avoided, and a metal layer is deposited on the surface of the AlGaN barrier layer to serve as an upper electrode. When external pressure is applied to the device, polarization charges of the upper electrode and the lower electrode are changed due to the piezoelectric effect of the AlGaN material, and on the other hand, the energy level barrier at the interface of the AlGaN/GaN heterostructure is changed due to the external pressure, so that the charge density of two-dimensional electron gas is changed, and the charge barrier difference of the upper electrode and the lower electrode is changed, namely, the pressure induced barrier change effect. Therefore, the change of the external pressure is reflected by measuring the potential barrier difference of the upper electrode and the lower electrode, and the sensing and the detection of the pressure are realized.

Referring to fig. 2 and 3, according to some embodiments of the invention, a piezo barrier varying gallium nitride pressure sensor comprises: the GaN-based light-emitting diode comprises a first substrate 8 and an epitaxial structure, wherein the epitaxial structure comprises a GaN buffer layer 7, a GaN channel layer 6, an AlN insert layer 4, an AlGaN barrier layer 3 and a GaN cap layer 12 which are sequentially formed on the first substrate 8; wherein, the AlGaN barrier layer 3 is provided with a first groove, an ohmic contact layer is formed in the first groove, and the ohmic contact layer is communicated with a two-dimensional electron gas (2DEG) at the interface of the AlN insert layer 4 and the GaN channel layer 6 to form a lower electrode 2; an upper electrode 1 is formed on at least a part of the upper surface of the GaN cap layer 12; and a passivation layer 5, the passivation layer 5 covering at least a portion of the upper surface of the epitaxial structure.

The material of the first substrate 8 is not particularly limited, and can be selected by those skilled in the art according to actual needs. According to some embodiments of the present invention, the material of the first substrate 8 may be Si, SiC, GaN, or sapphire.

According to some embodiments of the present invention, the thickness of the GaN buffer layer 7 may be 0.5-10 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 9 μm, 10 μm, and the like. If the thickness of the GaN buffer layer 7 is too small, a large dislocation density of the epitaxial layer may result; if the thickness of the GaN buffer layer 7 is too large, poor epitaxial layer stress uniformity may result.

According to some embodiments of the present invention, the thickness of the GaN channel layer 6 may be 0.2-10 μm, such as 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 9 μm, 10 μm, and the like. If the thickness of the GaN channel layer 6 is too large, the stress distribution may be uneven.

According to some embodiments of the present invention, the AlN insert layer 4 may have a thickness of 0.5 to 3nm, for example, 0.5nm, 0.8nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, etc. If the AlN insertion layer 4 is too thick, extreme stress may be introduced, degrading the epitaxial quality of the AlGaN layer, resulting in reduced mobility.

According to some embodiments of the present invention, the AlGaN barrier layer 3 may have a thickness of 10 to 1000nm, for example, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 800nm, 900nm, 1000nm, or the like; the depth of the first groove is 10-1000 nm, such as 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 800nm, 900nm, 1000nm, etc. It is understood that the depth of the first recess may be determined according to the thickness of the AlGaN barrier layer so that the ohmic contact layer formed in the first recess is in gas communication with the two-dimensional electrons to form the lower electrode. If the thickness of the AlGaN barrier layer 3 is excessively small, the two-dimensional electron gas density may be low; if the AlGaN barrier layer 3 is too thick, the carrier mobility may be low.

According to some embodiments of the present invention, the thickness of the GaN cap layer 12 may be 0-10 nm, such as 0, 0.1nm, 1nm, 2nm, 3nm, 5nm, 8nm, 9nm, 10nm, etc. If the thickness of the GaN cap layer 12 is too small, the carrier concentration may be reduced; if the thickness of the GaN cap layer 12 is too large, contact resistance may increase, reducing two-dimensional electron gas mobility.

According to some embodiments of the present invention, the material of the upper electrode may be at least one selected from Ti, Cr, Ni, Pt, and Au.

According to some embodiments of the present invention, the passivation layer may be made of an inorganic material.

According to some embodiments of the invention, the inorganic material may be selected from at least one of silicon oxide, silicon nitride, aluminum oxide.

According to some embodiments of the present invention, the thickness of the passivation layer 5 may be 50 to 600nm, such as 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, etc. If the thickness of the passivation layer 5 is too small, the device may not be protected; if the thickness of the passivation layer 5 is too large, the transport of the two-dimensional electron gas may be affected.

According to some embodiments of the present invention, the passivation layer is made of a low stress material, and the stress of the low stress material may be in a range of 0 to 300MPa, such as 0, 50MPa, 100MPa, 150MPa, 200MPa, 250MPa, 300MPa, and the like. Therefore, the robustness and the performance of the device can be improved.

According to some embodiments of the present invention, the passivation layer has an electrode hole and an external electrode, and the external electrode is connected to the upper electrode and the lower electrode through the electrode hole. Therefore, the upper electrode and the lower electrode in the pressure sensor are respectively connected to the external potential measuring unit through the two external electrodes, and the potential difference of the upper electrode and the lower electrode can be obtained. Wherein, the external electrode can be patterned according to actual needs.

Referring to fig. 4 and 5, according to some embodiments of the present invention, in the piezobarrier-varying gallium nitride pressure sensor, a side surface of the first substrate 8 away from the epitaxial structure has a second groove thereon, and the piezobarrier-varying gallium nitride pressure sensor may further include: a bonding layer 9, a second substrate 10 and a reference pressure chamber 11. A bonding layer 9 is formed on a side surface of the first substrate 8 away from the epitaxial structure, and a second substrate 10 is bonded to the first substrate 8 through the bonding layer 9 and forms a reference pressure chamber 11 with the second groove. Thus, the reference pressure chamber 11 can be used as a pressure reference when measuring the external pressure, and the formed pressure sensor is a gauge pressure type pressure sensor. The bonding method of the second substrate 10 and the first substrate 8 may be, for example, direct bonding, anodic bonding, metal interlayer bonding, polymer bonding, or the like.

Accordingly, the pressure sensor without the bonding layer 9, the second substrate 10, the reference pressure chamber 11, and the like is a differential pressure type pressure sensor.

The material of the second substrate 10 is not particularly limited, and can be selected by those skilled in the art according to actual needs. According to some embodiments of the present invention, the material of the second substrate 10 may be silicon, glass, sapphire, or the like.

According to some embodiments of the present invention, the depth of the second groove may be 50 to 400 μm, such as 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, and the like. It will be appreciated that the depth of the second recess, i.e. the depth of the reference pressure chamber 11 formed after bonding the second substrate 10, may be determined according to the required range of the pressure sensor.

In addition, according to some embodiments of the present invention, in the pressure sensor without the bonding layer 9, the second substrate 10, the reference pressure chamber 11, and the like, the second groove may be formed on the surface of the first substrate 8 on the side away from the epitaxial structure.

According to some embodiments of the present invention, a projected area of the second groove on the first substrate may be larger than a projected area of the upper electrode on the first substrate (as shown in fig. 2 and 4) or smaller than a projected area of the upper electrode on the first substrate (as shown in fig. 3 and 5).

According to some embodiments of the present invention, the specific shape of the front electrode structure is not particularly limited, and may be, for example, a circle, a square, or other figure, and the front electrode structures shown in fig. 2 to 5 are circular.

In another aspect of the invention, the invention provides a method for preparing the piezoelectric barrier changing gallium nitride pressure sensor of the above embodiment. According to an embodiment of the invention, the method comprises: (1) forming an epitaxial structure on a first substrate, wherein the epitaxial structure comprises a GaN buffer layer, a GaN channel layer, an AlN insert layer, an AlGaN barrier layer and a GaN cap layer which are sequentially formed on the first substrate; (2) selectively etching the epitaxial structure to form an epitaxial table top; (3) selectively etching the AlGaN barrier layer to form a first groove, and preparing an ohmic contact layer communicated with two-dimensional electron gas in the first groove to form a lower electrode; (4) forming an upper electrode on at least part of the upper surface of the GaN cap layer; (5) and forming a passivation layer on at least part of the upper surface of the epitaxial structure to obtain the piezobarrier-variable gallium nitride pressure sensor. The pressure-induced potential barrier variable gallium nitride pressure sensor prepared by the method can directly measure the change of the external pressure according to the potential difference between the upper electrode and the lower electrode under the condition of no external driving voltage, namely, the zero power consumption detection of the change of the external pressure is realized under the condition of no external driving voltage.

According to some embodiments of the invention, the method further comprises: and forming an electrode hole on the passivation layer, and forming external electrodes respectively connected with the upper electrode and the lower electrode through the electrode hole. Therefore, the upper electrode and the lower electrode in the pressure sensor are respectively connected to the external potential measuring unit through the two external electrodes, and the potential difference of the upper electrode and the lower electrode can be obtained. Wherein, the external electrode can be patterned according to actual needs.

According to some embodiments of the invention, the method further comprises: selectively etching at least part of the surface of one side of the first substrate, which is far away from the epitaxial structure, to form a second groove; and bonding a second substrate on the surface of one side of the first substrate, which is far away from the epitaxial structure, so that the second substrate and the second groove form a reference pressure cavity. Thus, when measuring the external pressure, the reference pressure chamber can be used as a pressure reference, and the formed pressure sensor is a gauge pressure type pressure sensor. The specific manner of bonding the second substrate on the surface of the first substrate away from the epitaxial structure may be, for example, direct bonding, anodic bonding, metal interlayer bonding, polymer bonding, and the like.

In addition, it should be noted that all the features and advantages described above for the piezobarrier-changing gallium nitride pressure sensor are also applicable to the method for preparing the piezobarrier-changing gallium nitride pressure sensor, and are not described in detail herein.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.

Examples

(1) Selecting a Si substrate, pretreating the surface, and growing a 2 mu mGaN buffer layer;

(2) growing a 2 mu mGaN channel layer, a 2nm AlN insert layer, a 200nm AlGaN barrier layer and a 3nm GaN cap layer on the GaN buffer layer;

(3) selectively etching the epitaxial layer epitaxial structure by adopting an Inductively Coupled Plasma (ICP) etching device to form an etching table board, wherein the etching depth reaches the GaN channel layer;

(4) selectively etching an AlGaN barrier layer groove on the table top by adopting ICP etching equipment, wherein the etching depth is 180nm, and preparing an ohmic contact layer to be communicated with two-dimensional electron gas (2DEG) to form a lower electrode;

(5) depositing a metal layer (Ni/Au) on the GaN cap layer to form an upper electrode;

(6) depositing low-stress passivation layer silicon nitride by 300nm, etching to form an electrode hole, and then depositing and patterning a metal layer (Ti/Au) to form an interconnected electrode;

(7) selectively etching the Si substrate to form an etching groove by a deep silicon etching process, wherein the etching depth is 350 mu m;

(8) and selecting a proper bonding process to bond the GaN epitaxial wafer to another substrate to form the gauge pressure type pressure sensor.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.