Heterojunction high-electron-mobility field effect transistor for realizing electric field regulation and control based on polarization effect

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a heterojunction high-electron-mobility field effect transistor for realizing electric field regulation and control based on a polarization effect. The device sequentially comprises a substrate, a semiconductor epitaxial layer, a grid electrode, a source electrode and a drain electrode from bottom to top, the semiconductor epitaxial layer comprises a buffer layer, an Al (Ga) N layer, a Ga (Al) N layer and an AlGaN barrier layer from bottom to top; polarization charges are formed between the Al (Ga) N layer and the Ga (Al) N layer, and the surface electric field of the transistor device is regulated and controlled through the polarization electric field of the polarization charges. The surface electric field of the device is regulated and controlled through polarization charges generated by the polarization effect between the Al (Ga) N layer and the Ga (Al) N layer, so that the surface electric field of the device is distributed more uniformly; the device structure provided by the invention can weaken the requirement of the device for the metal field plate structure, reduces the process complexity of the device, and facilitates the improvement of the device yield and the device stability.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and more specifically, to a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect. Background Art

[0002] GaN materials have excellent physical properties, such as a large bandgap, a high critical breakdown field strength, a high electron saturation drift velocity, and good thermal conductivity. Moreover, due to spontaneous polarization and piezoelectric polarization in the AlGaN / GaN heterojunction, there is a two-dimensional electron gas with a high concentration and high mobility at the heterojunction interface. GaN-based power devices prepared based on the AlGaN / GaN heterojunction can achieve high power density, switching frequency, can operate in a higher environment, and achieve high radiation resistance. They have been widely used in consumer electronics and are also developing towards higher power levels and higher reliability levels.

[0003] Most common GaN-based power devices are lateral devices that utilize the two-dimensional electron gas at the AlGaN / GaN heterojunction for carrier transport. To enable the device to reach a relatively high off-state breakdown voltage, currently, GaN-based power devices use metal field plates with different structures to evenly distribute the electric field concentrated on the device surface under the off-state drain voltage. Common field plate structures include source field plates, gate field plates, etc. The source field plate structure is as Figure 1 shown, where the extension of the source metal covers the gate metal of the device to evenly distribute the electric field concentration effect on the side of the gate close to the drain under the off-state drain voltage of the device. The common gate field plate is as Figure 1 shown, where a part of the gate metal extends to the region between the gate and the drain of the device to evenly distribute the concentrated electric field on the side of the gate close to the drain.

[0004] In the prior art, multi-layer metal field plates are usually used at the position where the electric field of the device is concentrated under the off-state drain voltage, which increases the difficulty of the device manufacturing process, increases the manufacturing cost of the device, and the complex metal field plate structure may affect the capacitance characteristics of the device and seriously affect the switching speed of the device. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the complex field plate structure and complex manufacturing process of the prior art GaN-based power devices, and provide a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect, weakens the need for the metal field plate structure of the device, reduces the complexity of the device structure, and also reduces the difficulty of device manufacturing.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is:

[0007] Provided is a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect, which sequentially includes a substrate, a semiconductor epitaxial layer, a gate, a source, and a drain from bottom to top; the semiconductor epitaxial layer includes a buffer layer, an Al(Ga)N layer, a Ga(Al)N layer, and an AlGaN barrier layer from bottom to top; polarization charges are formed between the Al(Ga)N layer and the Ga(Al)N layer, and the surface electric field of the transistor device is regulated by the polarization electric field of the polarization charges.

[0008] For a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect in the present invention, the surface electric field of the device is regulated by the polarization charges generated by the polarization effect between the Al(Ga)N layer and the Ga(Al)N layer, making the surface electric field distribution of the device more uniform; the device structure provided by the present invention can weaken the requirement of the device for the metal field plate structure, reduce the process complexity of the device, and is beneficial to improving the device yield and device stability.

[0009] Further, the polarization intensity of the Al(Ga)N layer is higher than that of the Ga(Al)N layer, and negative polarization charges are generated at the interface between the Al(Ga)N layer and the Ga(Al)N layer. Due to the polarization effect between the two layers, negative polarization charges can be generated at the interface between the two layers. Through the influence of the polarization charges on the electric field, the surface electric field of the device is regulated and the electric field distribution is more uniform.

[0010] Further, when the transistor device is in the off state and the drain voltage increases to a specific value, the electric field on the drain side of the gate no longer changes with the drain voltage. At this time, the two-dimensional electron gas in the access area between the gate and the drain is completely depleted in the off state, and only positive polarization charges generated by polarization exist in the channel. At the same time, the two-dimensional hole gas formed by polarization between the AlGaN barrier layer, the Al(Ga)N layer, and the Ga(Al)N layer is depleted, and the capacitance size formed between the AlGaN barrier layer, the Al(Ga)N layer, and the Ga(Al)N layer no longer changes. The electron concentration on the drain side increases with the increase of the drain voltage, and the drain electric field increases, causing the electric field peak to shift. The electric field peak under the off-state drain voltage of the device shifts from the gate side of the gate-drain access area to the drain side, reducing the peak electric field on the device surface and making the electric field distribution more uniform.

[0011] Further, the electric field regulation effect can be changed by changing the thickness of the Al(Ga)N layer and / or the Ga(Al)N layer. The device structure provided by the present invention can improve the regulation effect on the surface electric field of the device by adjusting the thickness of the Al(Ga)N layer and the Ga(Al)N layer.

[0012] Further, the Al component content in the Al(Ga)N layer is higher than that in the Ga(Al)N layer, and the thickness of the Al(Ga)N layer is 500 nm to 800 nm. Through the above limitations, the regulation effect of the polarization charges formed between the Al(Ga)N layer and the Ga(Al)N layer on the electric field in the upper Ga(Al)N layer and the AlGaN barrier layer can be enhanced.

[0013] Further, the Al component content in the Ga(Al)N layer is lower than that in the Al(Ga)N layer, and the thickness of the Ga(Al)N layer is 50 nm to 300 nm. Through the above limitations, the regulation effect of the polarization charges formed between the Al(Ga)N layer and the Ga(Al)N layer on the electric field of the upper Ga(Al)N layer and the AlGaN barrier layer can be enhanced.

[0014] Further, a polarization effect is generated between the AlGaN barrier layer and the Ga(Al)N layer, and positive polarization charges are generated. A two-dimensional electron gas is formed between the AlGaN barrier layer and the Ga(Al)N layer to ensure the conduction characteristics of the device.

[0015] Further, the Al component content in the AlGaN barrier layer is higher than that in the Ga(Al)N layer, and the thickness of the AlGaN barrier layer is 5 nm to 30 nm. Through the above limitations, there is a sufficient polarization effect between the AlGaN barrier layer and the Ga(Al)N layer, positive polarization charges are generated, and a two-dimensional electron gas with a high enough concentration is formed between the AlGaN barrier layer and the Ga(Al)N layer to ensure excellent conduction characteristics of the device.

[0016] Further, the substrate includes a Si substrate, a sapphire substrate or a SiC substrate.

[0017] Further, the buffer layer is an AlN nucleation layer and AlN material formed by low-temperature growth. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlN material formed by low-temperature growth is 500 nm to 2 μm. The growth conditions of the AlN nucleation layer are inconsistent with those of the AlN material formed by low-temperature growth; or, the buffer layer is an AlN nucleation layer and an AlGaN material with a gradually changing Al composition. The Al composition of the AlGaN material gradually changes from 100% to 25% - 45%. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlGaN material is 500 nm to 2 μm; or, the buffer layer is an AlN nucleation layer and a superlattice material. The superlattice material is composed of repeated Al(Ga)N / (Al)GaN units. The thicknesses of the two components in each unit are 1 nm to 5 nm and 1 nm to 5 nm respectively. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the total thickness of the superlattice material is 500 nm to 2 μm.

[0018] The device structure of the present invention is applicable to different substrate types. Different buffer layer structures need to be adopted for corresponding different substrate materials to relieve the lattice mismatch and thermal adaptation between the substrate and the Al(Ga)N layer, Ga(Al)N layer, and AlGaN barrier layer, and improve the crystal quality of the top layer material.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. For a heterojunction high electron mobility field effect transistor based on polarization effect to achieve electric field regulation according to the present invention, the polarization charges generated by the polarization effect between the Al(Ga)N layer and the Ga(Al)N layer are used to regulate the surface electric field of the device, making the surface electric field distribution of the device more uniform; the device structure provided by the present invention can weaken the requirement of the device for the metal field plate structure, reduce the process complexity of the device, and is beneficial to improving the device yield and device stability.

[0021] 2. For a heterojunction high electron mobility field effect transistor based on polarization effect to achieve electric field regulation according to the present invention, by adjusting the thicknesses of the Al(Ga)N layer and the Ga(Al)N layer, the regulation effect on the surface electric field of the device is improved; when the thickness of the Ga(Al)N layer decreases, the electric field peak value of the device under the off-state drain voltage transfers from the gate side of the gate-drain access region to the drain side, reducing the surface peak electric field of the device and making the electric field distribution more uniform.

[0022] 3. A heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to the present invention can generate sufficient polarization effect between the AlGaN barrier layer and the Ga(Al)N layer to generate positive polarization charges, so as to form a two-dimensional electron gas with a sufficiently high concentration between the AlGaN barrier layer and the Ga(Al)N layer, thereby ensuring excellent conduction characteristics of the device.

[0023] 4. A heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to the present invention can adjust the internal electric field of the device on the basis of realizing high conduction characteristics and high switching frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of an existing GaN-based power device;

[0025] Figure 2 is a schematic structural diagram of a heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to the present invention;

[0026] Figure 3 is an electric field distribution diagram of the AlGaN barrier layer of a device with different Ga(Al)N thicknesses of a heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to the present invention under the off-state drain voltage;

[0027] Figure 4 is the overall electric field distribution of a device with different Ga(Al)N thicknesses of a heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to the present invention under the off-state drain voltage.

[0028] In the drawings: 1. Substrate; 2. Buffer layer; 3. Al(Ga)N layer; 4. Ga(Al)N layer; 5. AlGaN barrier layer; 6. Gate; 7. Source; 8. Drain. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The present invention will be further described below in conjunction with the specific embodiments. Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0030] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing the present invention 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. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and should not be construed as a limitation of the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0031] Embodiment 1

[0032] This embodiment is the first embodiment of a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect. It sequentially includes a substrate 1, a semiconductor epitaxial layer, a gate 6, a source 7, and a drain 8 from bottom to top; the semiconductor epitaxial layer includes a buffer layer 2, an Al(Ga)N layer 3, a Ga(Al)N layer 4, and an AlGaN barrier layer 5 from bottom to top; polarization charges are formed between the Al(Ga)N layer 3 and the Ga(Al)N layer 4, and the surface electric field of the transistor device is regulated through the polarization electric field of the polarization charges.

[0033] In this embodiment, the polarization intensity of the Al(Ga)N layer 3 is higher than that of the Ga(Al)N layer 4, and negative polarization charges are generated at the interface between the Al(Ga)N layer 3 and the Ga(Al)N layer 4. Due to the polarization effect between the two layers, negative polarization charges can be generated at the interface between the two layers. Through the influence of the polarization charges on the electric field, the surface electric field of the device is regulated, and the electric field distribution becomes more uniform.

[0034] In this embodiment, as Figure 3 shown and Figure 4 shown, the electric field regulation effect can be changed by changing the thickness of the Al(Ga)N layer 3 and / or the Ga(Al)N layer 4. By adjusting the thickness of the Al(Ga)N layer 3 and the Ga(Al)N layer 4, the regulation effect on the surface electric field of the device is improved.

[0035] In this embodiment, when the transistor device is in the off state, the voltage of the drain 8 increases to a specific value, and the electric field on the drain 8 side of the gate 6 bias no longer changes with the drain 8 voltage. At this time, the two-dimensional electron gas in the access region between the gate 6 and the drain 8 is completely depleted in the off state, and only positive polarization charges generated by polarization exist in the channel. At the same time, the two-dimensional hole gas formed by the polarization between the Al(Ga)N layer 3 and the Ga(Al)N layer 4 is depleted, and the capacitance formed between the AlGaN barrier layer 5, the Al(Ga)N layer 3 and the Ga(Al)N layer 4 no longer changes. The electron concentration on the drain 8 side increases with the increase of the drain 8 voltage, and the drain 8 electric field increases, causing the peak of the electric field to shift. The peak of the electric field at the drain 8 voltage in the off state of the device shifts from the gate 6 side of the gate-drain access region to the drain 8 side, reducing the peak electric field on the device surface and making the electric field distribution more uniform.

[0036] In this embodiment, the Al component content in the Al(Ga)N layer 3 is higher than the Al component content in the Ga(Al)N layer 4, and the thickness of the Al(Ga)N layer 3 is 500 nm to 800 nm. Through the above limitations, the regulation effect of the polarization charges formed between the Al(Ga)N layer 3 and the Ga(Al)N layer 4 on the electric field in the upper Ga(Al)N layer 4 and the AlGaN barrier layer 5 can be strengthened.

[0037] In this embodiment, the Al component content in the Ga(Al)N layer 4 is lower than the Al component content in the Al(Ga)N layer 3, and the thickness of the Ga(Al)N layer 4 is 50 nm to 300 nm. Through the above limitations, the regulation effect of the polarization charges formed between the Al(Ga)N layer 3 and the Ga(Al)N layer 4 on the electric field of the upper Ga(Al)N layer 4 and the AlGaN barrier layer 5 can be strengthened.

[0038] In this embodiment, the Al component content in the AlGaN barrier layer 5 is higher than the Al component content in the Ga(Al)N layer 4, and the thickness of the AlGaN barrier layer 5 is 5 nm to 30 nm. Through the above limitations, there is enough polarization effect between the AlGaN barrier layer 5 and the Ga(Al)N layer 4 to generate positive polarization charges, and a two-dimensional electron gas with a high enough concentration is formed between the AlGaN barrier layer 5 and the Ga(Al)N layer 4 to ensure excellent conduction characteristics of the device.

[0039] The transistor device provided in this embodiment regulates the surface electric field of the device through the polarization charges generated by the polarization effect between the Al(Ga)N layer 3 and the Ga(Al)N layer 4, making the surface electric field distribution of the device more uniform; the device structure provided in this embodiment can weaken the device's demand for the metal field plate structure, reduce the process complexity of the device, and is beneficial to improving the device yield and device stability.

[0040] The transistor device provided in this embodiment improves the regulation of the device surface electric field by adjusting the thicknesses of the Al(Ga)N layer 3 and the Ga(Al)N layer 4; when the thickness of the Ga(Al)N layer 4 decreases, the peak electric field of the device under the off-state drain 8 voltage transfers from the gate 6 side of the gate-drain access region to the drain 8 side, reducing the surface peak electric field of the device and making the electric field distribution more uniform.

[0041] The transistor device provided in this embodiment can generate a sufficient polarization effect between the AlGaN barrier layer 5 and the Ga(Al)N layer 4 to generate positive polarization charges, so as to form a two-dimensional electron gas with a high enough concentration between the AlGaN barrier layer 5 and the Ga(Al)N layer 4, thereby ensuring excellent conduction characteristics of the device. The internal electric field of the device can be adjusted on the basis of achieving high conduction characteristics and high switching frequencies.

[0042] Embodiment Two

[0043] This embodiment is the second embodiment of a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect. This embodiment is similar to Embodiment One, and the difference lies in that, in this embodiment, the substrate 1 is a Si substrate 1, a sapphire substrate 1, or a SiC substrate 1.

[0044] Embodiment Three

[0045] This embodiment is the third embodiment of a heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect. This embodiment is similar to Embodiment One, and the difference lies in that, in this embodiment, the buffer layer 2 is an AlN nucleation layer and AlN material grown at low temperature. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlN material grown at low temperature is 500 nm to 2 μm. The growth conditions of the AlN nucleation layer are inconsistent with those of the AlN material grown at low temperature; or, the buffer layer 2 is an AlN nucleation layer and an AlGaN material with a gradually changing Al composition. The Al composition of the AlGaN material gradually changes from 100% to 25% - 45%. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlGaN material is 500 nm to 2 μm; or, the buffer layer 2 is an AlN nucleation layer and a superlattice material. The superlattice material is composed of repeated Al(Ga)N / (Al)GaN units. The thicknesses of the two components in each unit are 1 nm to 5 nm and 1 nm to 5 nm respectively. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the total thickness of the superlattice material is 500 nm to 2 μm.

[0046] The device structure of the present invention is applicable to different types of substrate 1. For different corresponding substrate 1 materials, different buffer layer 2 structures need to be adopted to alleviate the lattice mismatch and thermal adaptation between substrate 1 and Al(Ga)N layer 3, Ga(Al)N layer 4 of Al(Ga)N and Ga(Al)N, and AlGaN barrier layer 5, and improve the crystal quality of the top layer material.

[0047] In the specific content of the above specific embodiments, each technical feature can be combined arbitrarily without contradiction. For the sake of concise description, not all possible combinations of the above technical features are described. However, as long as the combinations of these technical features do not conflict, they should be considered to be within the scope described in this specification.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A heterojunction high electron mobility field effect transistor that realizes electric field regulation based on the polarization effect, characterized in that It includes a substrate (1), a semiconductor epitaxial layer, a gate (6), a source (7), and a drain (8) from bottom to top in sequence; the semiconductor epitaxial layer includes a buffer layer (2), an Al(Ga)N layer (3), a Ga(Al)N layer (4), and an AlGaN barrier layer (5) from bottom to top; polarization charges are formed between the Al(Ga)N layer (3) and the Ga(Al)N layer (4), and the surface electric field of the transistor device is regulated by the polarization electric field of the polarization charges.

2. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 1, characterized in that, The polarization intensity of the Al(Ga)N layer (3) is higher than that of the Ga(Al)N layer (4), and negative polarization charges are generated at the interface between the Al(Ga)N layer (3) and the Ga(Al)N layer (4).

3. The heterojunction high electron mobility field effect transistor for realizing electric field regulation based on the polarization effect according to claim 1, wherein, When the transistor device is in the off state, when the voltage of the drain (8) increases to a specific value, the electric field on the side of the gate (6) biased towards the drain (8) no longer changes with the voltage of the drain (8). At this time, the two-dimensional electron gas in the access area between the gate (6) and the drain (8) is completely depleted in the off state, and only positive polarization charges generated by polarization exist in the channel. At the same time, the two-dimensional hole gas formed by polarization between the AlGaN barrier layer (5), the Al(Ga)N layer (3), and the Ga(Al)N layer (4) is depleted, and the capacitance between the AlGaN barrier layer (5), the Al(Ga)N layer (3), and the Ga(Al)N layer (4) no longer changes. The electron concentration on the side of the drain (8) increases with the increase of the voltage of the drain (8), and the electric field of the drain (8) increases, causing the peak of the electric field to shift.

4. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 2, characterized in that, By changing the thickness of the Al(Ga)N layer (3) and / or the Ga(Al)N layer (4), the electric field regulation effect can be changed.

5. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 4, wherein The Al component content in the Al(Ga)N layer (3) is higher than that in the Ga(Al)N layer (4), and the thickness of the Al(Ga)N layer (3) is 500 nm to 800 nm.

6. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 4, characterized in that, The Al component content in the Ga(Al)N layer (4) is lower than that in the Al(Ga)N layer (3), and the thickness of the Ga(Al)N layer (4) is 50 nm to 300 nm.

7. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to any one of claims 1 to 6, characterized in that, A polarization effect is generated between the AlGaN barrier layer (5) and the Ga(Al)N layer (4), and positive polarization charges are generated, and a two-dimensional electron gas is formed between the AlGaN barrier layer (5) and the Ga(Al)N layer (4) to ensure the conduction characteristics of the device.

8. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 7, characterized in that, The Al component content in the AlGaN barrier layer (5) is higher than that in the Ga(Al)N layer (4), and the thickness of the AlGaN barrier layer (5) is 5 nm to 30 nm.

9. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 7, wherein The substrate (1) includes a Si substrate (1), a sapphire substrate (1), or a SiC substrate (1).

10. The heterojunction high electron mobility field effect transistor based on polarization effect for realizing electric field regulation according to claim 9, wherein The buffer layer (2) is an AlN nucleation layer and an AlN material formed by low-temperature growth. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlN material formed by low-temperature growth is 500 nm to 2 μm. The growth conditions of the AlN nucleation layer are inconsistent with those of the AlN material formed by low-temperature growth; or, the buffer layer (2) is an AlN nucleation layer and an AlGaN material with a gradually changing Al composition. The Al composition of the AlGaN material gradually changes from 100% to 25% - 45%. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the thickness of the AlGaN material is 500 nm to 2 μm; or, the buffer layer (2) is an AlN nucleation layer and a superlattice material. The superlattice material is composed of repeated Al(Ga)N / (Al)GaN units. The thicknesses of the two components in each unit are 1 nm to 5 nm and 1 nm to 5 nm respectively. The thickness of the AlN nucleation layer is 100 nm to 500 nm, and the total thickness of the superlattice material is 500 nm to 2 μm.

Images