CN103123934B - The gallium nitride based transistor structure with high electron mobility of tool barrier layer and manufacture method - Google Patents

Abstract

A GaN-based high electron mobility transistor structure with a potential barrier layer, comprising: a substrate; a nucleation layer fabricated on the substrate; a non-intentionally doped high-resistance layer, the non-intentionally doped An intentionally doped high-resistance layer is fabricated on the nucleation layer; an unintentionally doped high-mobility channel layer is fabricated on the unintentionally doped high-resistance layer; A doped aluminum nitride space layer, the non-intentionally doped aluminum nitride space layer is fabricated on the unintentionally doped high-mobility channel layer; an unintentionally doped barrier layer, the unintentionally doped barrier layer is fabricated On the unintentionally doped aluminum nitride space layer; an unintentionally doped GaN cap layer, the unintentionally doped GaN cap layer is formed on the unintentionally doped barrier layer. The invention can increase the confinement effect on the two-dimensional electron gas of the channel, improve the output power of the developed device, and reduce the gate current of the device at the same time.

Description

Gallium Nitride-based High Electron Mobility Transistor Structure and Fabrication Method with Potential Barrier Layer

technical field

The invention belongs to the technical field of semiconductors, in particular to a gallium nitride-based high electron mobility transistor (HEMT) structure and manufacturing method with a potential barrier layer. The transistor uses a combination of non-intentionally doped aluminum gallium nitride and aluminum nitride The new barrier layer and high-mobility gallium nitride channel layer can significantly increase the two-dimensional electron gas surface density and the confinement effect on the two-dimensional electron gas, reduce the influence of the heterojunction interface on the electronic properties of the channel, and improve The performance of the developed device.

Background technique

Gallium nitride-based semiconductor materials have excellent physical and chemical properties, and are especially suitable for the preparation of high-frequency, high-power, high-electron mobility transistors. GaN-based high electron mobility transistors have high breakdown voltage, high operating frequency, high output power, and good radiation resistance. They are used in wireless communications, radar, aerospace, automotive electronics, automation control, oil exploration, high-temperature radiation environments, etc There are broad application prospects.

The principle of the high electron mobility transistor is: due to the different band gaps of the two materials that make up the heterojunction, a potential barrier and a potential well are formed at the heterojunction interface, and the free electrons generated by the polarization effect or modulation doping , accumulate in the triangular potential well of the non-doped GaN layer close to the interface, forming a two-dimensional electron gas. Since these electrons in the potential well are spatially separated from the ionized impurities in the potential barrier, Coulomb scattering is greatly reduced, thus significantly The electron mobility of the material is improved. After the device is developed, the two-dimensional electron gas density at the heterojunction interface can be controlled by adjusting the bias voltage of the gate electrode, and high-frequency microwave signals can be amplified under a certain DC bias voltage.

The two-dimensional electron gas surface density and mobility are important parameters to characterize the quality of high electron mobility transistor structure materials. While reducing the barrier thickness, increasing the two-dimensional electron gas surface density and mobility in the channel is the key to improving the GaN Based on the operating frequency of high electron mobility transistors, it is an important measure to enhance the output current density and power density. Before the present invention, in order to improve the two-dimensional electron gas surface density and the mobility of GaN-based high electron mobility transistor structural materials, two methods are generally adopted: (1) n-type doping is carried out to the AlGaN barrier layer , can increase the two-dimensional electron gas surface density in the channel to a certain extent. However, doping will reduce the integrity of the material lattice, resulting in a decrease in the crystal quality of the AlGaN layer, increasing the interface roughness between the GaN and AlGaN layers, and reducing the electron mobility; (2) using high Al Composition barrier layer AlGaN/GaN HEMT structure, with the increase of barrier layer Al composition, the heterojunction band order and polarization electric field increase, which can significantly increase the two-dimensional electron gas surface density. However, when the Al composition is high, the large lattice mismatch will lead to the deterioration of the crystal quality, surface and interface quality of the AlGaN barrier layer, and the strain-induced deep level defects will increase, which will enhance the scattering and reduce the mobility; At the same time, when the Al composition is too high, the large lattice mismatch limits the thickness of the barrier layer, making it difficult to generate a strong two-dimensional electron gas.

Contents of the invention

The purpose of the present invention is to provide a gallium nitride-based HEMT structure with a barrier layer and a manufacturing method. A new type of barrier layer is formed by inserting a thin layer of aluminum nitride, which has a higher two-dimensional electron gas surface density, and can increase the barrier height of the two-dimensional electron gas in the channel, and more effectively limit the flow of channel electrons to the barrier layer. Leakage, thereby increasing the confinement effect on the channel two-dimensional electron gas, improving the output power of the developed device, and at the same time the gate current of the device is expected to be reduced.

The invention provides a GaN-based high electron mobility transistor structure with a barrier layer, comprising:

a substrate;

a nucleation layer, the nucleation layer is fabricated on the substrate;

An unintentionally doped high-resistance layer formed on the nucleation layer;

An unintentionally doped high-mobility channel layer, the unintentionally doped high-mobility channel layer is fabricated on the unintentionally doped high-resistance layer;

An unintentionally doped aluminum nitride spacer layer, the unintentionally doped aluminum nitride spacer layer is fabricated on the unintentionally doped high-mobility channel layer;

An unintentionally doped barrier layer formed on the unintentionally doped aluminum nitride spacer layer;

An unintentionally doped GaN cap layer is formed on the unintentionally doped barrier layer.

The present invention also provides a method for manufacturing a gallium nitride-based high electron mobility transistor with a potential barrier layer, comprising the following steps:

Step 1: Select a substrate;

Step 2: growing a nucleation layer on the substrate with a growth thickness of 0.01-0.50 μm;

Step 3: growing a non-intentionally doped high-resistance layer on the nucleation layer;

Step 4: growing an unintentionally doped high-mobility channel layer on the unintentionally doped high-resistance layer;

Step 5: growing an unintentionally doped aluminum nitride spacer layer on the unintentionally doped high-mobility channel layer, with a growth thickness of 0.7-3 nm;

Step 6: growing an unintentionally doped new barrier layer on the unintentionally doped aluminum nitride space layer;

Step 7: growing an unintentionally doped gallium nitride capping layer on the unintentionally doped novel barrier layer with a thickness of 1-5 nm to complete the preparation.

The invention can reduce the process difficulty and process steps, and through the introduced barrier layer structure, that is, a thin aluminum nitride layer is inserted in the traditional aluminum gallium nitride barrier layer, low defect density and high two-dimensional electron gas can be obtained At the same time, it can significantly increase the barrier height that restricts channel electrons, which is expected to reduce the gate leakage of the device. The invention can remarkably improve and enhance the performance of gallium nitride-based high-temperature, high-frequency, high-power devices and circuits.

Description of drawings

For further illustrating content of the present invention, below in conjunction with accompanying drawing, the present invention is described in detail, wherein:

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the production flowchart of the present invention;

Figure 3 (a) has a traditional barrier layer and (b) has a new barrier layer GaN-based HEMT structure two-dimensional electron gas distribution and structure band diagram.

Detailed ways

Please refer to Fig. 1, a GaN-based HEMT structure with a barrier layer of the present invention, including:

A substrate 10, the substrate 10 is a silicon carbide substrate or a sapphire substrate or a silicon substrate, and the thickness of the substrate 10 is 300-650 μm.

A nucleation layer 20 is formed on the substrate 10 . The nucleation layer 20 is GaN or AlN or AlGaN with a thickness of 0.01-0.50 μm, preferably 0.03-0.30 μm.

A non-intentionally doped high-resistance layer 30, the non-intentionally doped high-resistance layer 30 is fabricated on the nucleation layer 20, and the resistivity is greater than 10 ⁶ Ω.cm. The material of the non-intentionally doped high-resistance layer 30 is _{AlyGa1 -yN} , the aluminum composition is 0≤y≤0.15, and the thickness is 1-5 μm. The non-intentionally doped high-resistance layer 30 has four functions, one is to reduce the lattice mismatch between the substrate and the epitaxial layer as a buffer layer, and improve the crystal quality of the epitaxial layer; Device leakage, the third is to raise the barrier height of the channel on the buffer layer substrate side as a back barrier layer, reduce the leakage of channel electrons in the buffer layer under high field, improve the stability of materials and devices, and the fourth is to improve The breakdown voltage of the device increases the output power of the device.

An unintentionally doped high-mobility channel layer 40, the unintentionally doped high-mobility channel layer 40 is fabricated on the unintentionally doped high-resistance layer 30, and the carrier mobility is greater than 500 cm ² /Vs. The material of the non-intentionally doped high-mobility channel layer 40 is gallium nitride, and the thickness is 10-100 nm. The non-intentionally doped high-mobility channel layer 40 provides a good channel for the two-dimensional electron gas, and also significantly improves the mobility of the two-dimensional electron gas in the channel.

An unintentionally doped AlN space layer 50 , the unintentionally doped AlN space layer 50 is fabricated on the unintentionally doped high-mobility GaN channel layer 40 . The thickness of the non-intentionally doped aluminum nitride space layer 50 is 0.7-3 nm, preferably 1 nm. The non-intentionally doped aluminum nitride space layer 50 has three functions: one is to use the binary compound to separate the channel electrons from the non-intentionally doped new barrier layer 60 of the multi-component compound, reduce the alloy scattering of electrons, and further improve the channel Two-dimensional electron gas mobility; the second is to use its large forbidden band width to increase the potential barrier and effectively prevent electrons from leaking to the non-intentionally doped new barrier layer 60 and the surface; the third is to use the strong pole of the aluminum nitride material The effect of ionization induces more electrons in the channel and increases the surface density of the two-dimensional electron gas.

An unintentionally doped barrier layer 60 is fabricated on the unintentionally doped aluminum nitride spacer layer 50 . The material of the non-intentionally doped barrier layer 60 is a composite layer of AlxGa1 _{- xN} and AlN, the total growth thickness is 10-30nm, the aluminum composition of AlGaN is 0.10≤x≤0.35, nitrided The thickness of aluminum is 0.7-3nm, the number is at least 1 layer, and it is inserted into any position in AlGaN. The advantages of the non-intentionally doped barrier layer 60 are: firstly, the thin aluminum nitride layer with a strong polarization effect can induce a higher density of two-dimensional electron gas, while maintaining the high crystal quality of the barrier material, Prevent the reduction of channel electron mobility; the second is to increase the effective barrier height of channel electrons and reduce the gate current when the device is working.

An unintentionally doped GaN cap layer 70, the unintentionally doped GaN cap layer 70 is fabricated on the unintentionally doped barrier layer 60, with a thickness of 1-5 nm. The non-intentionally doped GaN capping layer 70 serves as a capping layer, which can reduce device process difficulty.

Please refer to FIG. 2 again and refer to FIG. 1. The present invention also provides a method for manufacturing a GaN-based HEMT with a barrier layer, which includes the following steps:

Step 1: Select a substrate 10, the substrate 10 is a silicon carbide substrate or a sapphire substrate or a silicon substrate, and the thickness of the substrate 10 is 300-650 μm;

Step 2: growing a layer of nucleation layer 20 on the substrate 10, the nucleation layer 20 is gallium nitride or aluminum nitride or aluminum gallium nitride, and the growth thickness of the nucleation layer 20 is 0.01-0.50 μm, preferably 0.03-0.30μm;

Step 3: grow an unintentionally doped high-resistance layer 30 on the nucleation layer 20, the resistivity is greater than 10 ⁶ Ω.cm, the material of the unintentionally doped high-resistance layer 30 is _{AlyGa1 -yN} , aluminum group Divided into 0≤y≤0.15, the growth thickness is 1-5μm. The room temperature resistivity of the non-intentionally doped high-resistance layer 30 is greater than 1×10 ⁶ Ω·cm, preferably greater than 1×10 ⁸ Ω·cm;

Step 4: growing an unintentionally doped high-mobility channel layer 40 on the unintentionally doped high-resistance layer 30, the carrier mobility is greater than 500 cm ² /Vs, and the unintentionally doped high-mobility channel layer 40 The material is gallium nitride, and the growth thickness is 10-100nm. The non-intentionally doped high-mobility channel layer 40 is a two-dimensional electron gas operating channel, and the mobility at room temperature is greater than 500 cm ² /Vs, preferably greater than 700 cm ² /Vs;

Step 5: growing an unintentionally doped aluminum nitride space layer 50 on the unintentionally doped high-mobility channel layer 40 to a thickness of 0.7-3 nm, preferably 1 nm. The non-intentionally doped aluminum nitride space layer 50 can increase the surface density and mobility of 2DEG, reduce the influence of the heterojunction interface on the two-dimensional electron gas of the channel, and improve the comprehensive performance of the heterostructure material;

Step 6: growing an unintentionally doped barrier layer 60 on the unintentionally doped AlN space layer 50 . The material of the non-intentionally doped barrier layer 60 is a composite layer of AlxGa1 _{- xN} and AlN, the total growth thickness is 10-30nm, the aluminum composition of AlGaN is 0.10≤x≤0.35, nitrided The thickness of aluminum is 0.7-3nm, the number is at least 1 layer, inserted into any position in AlGaN;

Step 7: growing an unintentionally doped GaN capping layer 70 on the unintentionally doped barrier layer 60, the thickness of the unintentionally doped GaN capping layer 70 is 1-5 nm, and the preparation is completed.

The fabrication method includes but not limited to metal organic chemical vapor deposition, molecular beam epitaxy and vapor phase epitaxy, and metal organic chemical vapor deposition is preferred.

Example:

The present invention provides a GaN-based HEMT structure with a barrier layer, which includes:

A substrate 10, the material of which is sapphire.

A nucleation layer 20 is formed on the substrate 10 . The material of the nucleation layer 20 is low-temperature gallium nitride with a thickness of 100 nm;

An unintentionally doped high-resistance layer 30 is fabricated on the nucleation layer 20 . The aluminum composition y of the unintentionally doped high resistance layer 30 is 0, the material of the unintentionally doped high resistance layer 30 is gallium nitride, and the thickness is 3 μm.

An unintentionally doped high mobility channel layer 40 is fabricated on the unintentionally doped high resistance layer 30 . The material of the non-intentionally doped high-mobility layer channel layer 40 is gallium nitride with a thickness of 30 nm.

An unintentionally doped AlN space layer 50 , the unintentionally doped AlN space layer 50 is fabricated on the unintentionally doped high-mobility GaN channel layer 40 . The thickness of the non-intentionally doped aluminum nitride space layer 50 is 1 nm.

An unintentionally doped barrier layer 60 is fabricated on the unintentionally doped aluminum nitride spacer layer 50 . The material of the non-intentionally doped barrier layer 60 is a composite layer of Al _0.25 Ga _0.75 N and AlN, the total thickness is 21nm, the aluminum component of AlGaN is 0.25, the thickness of aluminum nitride is 1nm, and the number is 1 layer, the specific position inserted into AlGaN is as follows: Al _0.25 Ga _0.75 N (15nm)/AlN (1nm)/Al _0.25 Ga _0.75 N (5nm).

An unintentionally doped GaN capping layer 70, the unintentionally doped GaN capping layer 70 is fabricated on the unintentionally doped new barrier layer 60, with a thickness of 3nm.

The invention provides a method for manufacturing a GaN-based HEMT with a barrier layer, which adopts a metal-organic chemical vapor deposition method, and includes the following steps:

Step 1: select a substrate 10, which is a sapphire substrate;

Step 2: growing a nucleation layer 20 on the substrate 10, the material is gallium nitride, the growth temperature is 500-600°C, the growth pressure is 53.34-80.01kPa, and the growth thickness is 100nm;

Step 3: growing an unintentionally doped high-resistance layer 30 on the nucleation layer 20, the material is gallium nitride, the growth temperature is 900-1100°C, the preferred value range is 1020-1100°C, and the growth thickness is 3 μm;

Step 4: growing an unintentionally doped high-mobility channel layer 40 on the unintentionally doped high-resistance layer 30, the material is gallium nitride, the growth thickness is 30nm, the growth temperature is 900-1100°C, and the room temperature mobility is greater than 500cm ² /Vs, preferably greater than 700cm ² /Vs;

Step 5: growing an unintentionally doped aluminum nitride spacer layer 50 on the unintentionally doped high-mobility channel layer 40 with a growth thickness of 1 nm and a growth temperature of 850-1150° C.;

Step 6: growing an unintentionally doped barrier layer 60 on the unintentionally doped aluminum nitride space layer 50, the unintentionally doped barrier layer 60 is a composite layer of Al _0.25 Ga _0.75 N and AlN, with a total growth thickness of 21nm, the growth temperature is 850-1150℃, the aluminum component of aluminum gallium nitride is 0.25, the thickness of aluminum nitride is 1nm, and the number is 1 layer. The specific growth structure is as follows: Al _0.25 Ga _0.75 N(15nm)/AlN( 1nm)/Al _0.25 Ga _0.75 N(5nm);

Step 7: growing an unintentionally doped gallium nitride cap layer 70 on the unintentionally doped barrier layer 60 with a thickness of 3 nm and a growth temperature of 850-1150° C. to complete the preparation.

Figure 3 (b) calculates the energy band and electron distribution diagram of the HEMT structure with the new barrier layer in the embodiment, and Figure 3 (a) is GaN (3nm)/Al _0.25 Ga _0.75 N (20nm) with the traditional barrier layer )/AlN(1nm)/GaN(30nm) HEMT structure energy band and electron distribution diagram. Comparing these two figures, by inserting a layer of 1nm aluminum nitride thin layer in the traditional barrier layer, the barrier height is increased by about 0.8eV, which is expected to reduce the gate current of the device; at the same time, the 2DEG area density is changed from the original 1.13 ×10 ¹³ cm ^-2 increases to 1.32×1 ¹³ cm ^-2 , with an increase of 16.8%.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. A GaN-based high electron mobility transistor structure with a potential barrier layer, comprising: a substrate; a nucleation layer, the nucleation layer is fabricated on the substrate; An unintentionally doped high-resistance layer formed on the nucleation layer; An unintentionally doped high-mobility channel layer, the unintentionally doped high-mobility channel layer is fabricated on the unintentionally doped high-resistance layer; An unintentionally doped aluminum nitride spacer layer, the unintentionally doped aluminum nitride spacer layer is fabricated on the unintentionally doped high-mobility channel layer; An unintentionally doped barrier layer, the unintentionally doped barrier layer is fabricated on the unintentionally doped aluminum nitride space layer, and the materials of the unintentionally doped barrier layer are AlxGa1 _{- xN} and AlN The composite layer has a total thickness of 10-30nm, the aluminum composition of aluminum gallium nitride is 0.10≤x≤0.35, the thickness of aluminum nitride is 0.7-3nm, and the number of aluminum nitride is at least 1 layer; An unintentionally doped GaN cap layer is formed on the unintentionally doped barrier layer. 2. The gallium nitride-based high electron mobility transistor structure with a potential barrier layer according to claim 1, wherein the material of the non-intentionally doped high-resistance layer is Al _y Ga _1-y N, and the aluminum composition is 0≤ y≤0.15, the thickness is 1-5μm. 3 . The gallium nitride-based high electron mobility transistor structure with a barrier layer according to claim 1 , wherein the material of the non-intentionally doped high mobility channel layer is gallium nitride, and the thickness is 10-100 nm. 4. A method for manufacturing a gallium nitride-based high electron mobility transistor with a potential barrier layer, comprising the steps of: Step 1: Select a substrate; Step 2: growing a nucleation layer on the substrate with a growth thickness of 0.01-0.50 μm; Step 3: growing a non-intentionally doped high-resistance layer on the nucleation layer; Step 4: growing an unintentionally doped high-mobility channel layer on the unintentionally doped high-resistance layer; Step 5: growing an unintentionally doped aluminum nitride spacer layer on the unintentionally doped high-mobility channel layer, with a growth thickness of 0.73 nm; Step 6: growing an unintentionally doped barrier layer on the unintentionally doped aluminum nitride spacer layer, the material of the unintentionally doped barrier layer is a composite layer of AlxGa1 _{- xN} and AlN, with a total thickness of 10-30nm, the aluminum composition of aluminum gallium nitride is 0.10≤x≤0.35, the thickness of aluminum nitride is 0.7-3nm, and the number of aluminum nitride is at least 1 layer; Step 7: growing an unintentionally doped gallium nitride capping layer on the unintentionally doped barrier layer with a thickness of 1-5 nm to complete the preparation. 5. the fabrication method of the GaN-based high electron mobility transistor with barrier layer according to claim 4, wherein the material of the non-intentionally doped high-resistance layer is Al _y Ga _1-y N, and the aluminum composition is 0≤y≤0.15, the thickness is 1-5μm. 6. The method for manufacturing a gallium nitride-based high electron mobility transistor with a potential barrier layer according to claim 4, wherein the material of the non-intentionally doped high mobility channel layer is gallium nitride, and the thickness is 10-100nm .