CN210073765U

CN210073765U - AlGaN double-heterojunction high-resistance buffer layer epitaxial structure

Info

Publication number: CN210073765U
Application number: CN201921214481.0U
Authority: CN
Inventors: 林志东; 房育涛; 刘波亭; 林云昊; 许燕丽; 张恺玄
Original assignee: Xiamen Sanan Integrated Circuit Co Ltd
Current assignee: Xiamen Sanan Integrated Circuit Co Ltd
Priority date: 2019-07-30
Filing date: 2019-07-30
Publication date: 2020-02-14
Anticipated expiration: 2029-07-30

Abstract

The utility model discloses a two heterojunction high resistance buffer layer epitaxial structure of AlGaN, include by lower supreme range upon range of substrate, nucleation layer, the two heterojunction high resistance buffer layer of AlGaN and gaN layer that sets up: the AlGaN double-heterojunction high-resistance buffer layer comprises more than two AlGaN heterojunction structures, wherein the heterojunction structure of each period comprises two AlGaN layers, and the thickness range of one layer is 100-1000 nm; the thickness of the other layer is in the range of 1-99 nm. The utility model discloses thereby can reduce the background electron concentration on AlGaN layer and increase electron vertical direction scattering and realize the growth of high resistant buffer layer, obtain high-quality gaN base buffer layer.

Description

AlGaN double-heterojunction high-resistance buffer layer epitaxial structure

Technical Field

The utility model relates to a semiconductor device, in particular to AlGaN double-heterojunction high-resistance buffer layer epitaxial structure.

Background

The III-V group nitride (gallium nitride, aluminum nitride and alloy compounds thereof) has the advantages of large forbidden band width, high thermal conductivity, high saturated electron drift velocity and the like, and is widely used for high-temperature and high-voltage electronic devices. A gallium nitride based High Electron Mobility Transistor (HEMT) is a field effect Transistor having High operating voltage, small on-resistance, and High switching frequency, which is formed by forming two-dimensional Electron gas having High Mobility and High concentration at an AlGaN/GaN heterojunction interface by using the difference in forbidden bandwidth and polarization strength between an AlGaN layer and a GaN layer.

The leakage of the buffer layer in the gallium nitride-based HEMT device can not only deteriorate the pinch-off performance of the device, but also weaken the control capability of the grid on the channel current and deteriorate the overall performance of the device. Meanwhile, the electric leakage in the buffer layer can also cause the heat generation of the device to deteriorate the output characteristic of the device so as to influence the reliability and the service life of the device, and therefore, the preparation of the high-resistance GaN-based buffer layer is a key technology for the epitaxy of the high-performance HEMT device. In addition, the defect density (dislocation density, defect impurities, doping and the like) of the buffer layer can directly influence the two-dimensional electron gas mobility of the HEMT device, so that the on-resistance of the device is influenced, and therefore, the growth of the high-quality buffer layer is also a key technology for obtaining the high-performance HEMT.

Gallium nitride-based HEMT epitaxial wafers are typically grown on silicon carbide substrates, silicon substrates and sapphire substrates by heteroepitaxy using a Metal Organic Chemical Vapor Deposition (MOCVD) apparatus. The GaN-based epitaxial material grown by MOCVD has high background electron concentration (10) due to the existence of defects such as background oxygen doping, nitrogen vacancy and the like¹⁶-10¹⁷/cm³Left and right), it is necessary to reduce the background electron concentration of the GaN-based epitaxial material in order to obtain a GaN-based buffer layer with a high resistance. Methods for obtaining high-resistance GaN-based epitaxial materials can be generally classified into two main categories: one is to control the growth parameters (reaction chamber pressure, growth temperature, growth rate,V/III ratio, etc.) to increase the number of p-type impurities in the epitaxial material or trap the defect state density of electrons, thereby reducing the background electron concentration and further obtaining the high-resistance GaN-based buffer layer; the other method is to introduce an exogenous dopant containing metal elements such as Fe, Cr, Mg and the like in the epitaxial growth process of the GaN-based material to form deep level defects in forbidden bands or provide holes to compensate background electrons so as to obtain the GaN-based buffer layer with high resistance. The first method is to obtain a high-resistance GaN epitaxial layer by introducing defect impurities, so the quality of the epitaxial layer generally becomes poor, and in addition, the method for obtaining the high-resistance GaN by controlling growth conditions has strong equipment dependence and poor repeatability; in the second method, the introduced metal impurities generally have a strong memory effect and remain in the reaction chamber all the time, so that subsequent epitaxial materials are at risk of being contaminated by the metal impurities, and the introduced impurities can reduce the mobility of the channel 2DEG to influence the device characteristics.

Therefore, the present inventors have further studied and developed an AlGaN double-heterojunction high-resistance buffer layer epitaxial structure, and thus the present invention has been developed.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a two heterojunction high resistance buffer layer epitaxial structure of AlGaN is provided, thereby can reduce the background electron concentration on AlGaN layer and increase electron vertical direction scattering and realize the growth of high resistance buffer layer, obtain high-quality gaN base buffer layer.

In order to solve the technical problem, the technical solution of the utility model is that:

an AlGaN double-heterojunction high-resistance buffer layer epitaxial structure comprises a substrate, a nucleation layer, an AlGaN double-heterojunction high-resistance buffer layer and a GaN layer which are stacked from bottom to top: the AlGaN double-heterojunction high-resistance buffer layer comprises more than two heterojunction structures, wherein the heterojunction structure of each period comprises two AlGaN layers, and the thickness range of one layer is 100-1000 nm; the thickness of the other layer is in the range of 1-99 nm.

Further, the heterojunction structure is a heterojunction with a thin barrier.

Further, the two AlGaN layers are respectively Al_aGa_1-aN layer and Al_bGa_1-bN layer of said Al_aGa_1-aThe N layer is a low Al component layer, the Al_bGa_1-bThe N layer is a high Al component layer.

Further, the heterojunction structure is a heterojunction with a thin potential well.

Further, the two AlGaN layers are respectively Al_aGa_1-aN layer and Al_bGa_1-bN layer of said Al_aGa_1-aThe N layer is a high Al component layer, and the Al_bGa_1-bThe N layer is a low Al component layer.

Further, the heterojunction structure further comprises an Al component increasing layer and/or an Al component decreasing layer which is positioned between the two AlGaN layers.

Furthermore, the number of the AlGaN double-heterojunction high-resistance buffer layers is one group or multiple groups.

Further, the number of the heterojunction structure period is 2-100.

Further, the nucleation layer is specifically an AlN nucleation layer.

Further, the substrate is specifically a sapphire substrate, a silicon carbide substrate or a silicon substrate.

Since AlN has a forbidden band width of 6.2eV and GaN has a forbidden band width of only 3.4eV, a heterojunction structure having different forbidden band widths can be obtained by growing AlGaN having different Al compositions. III-V nitride crystals generally belong to the hexagonal system, and AlN and GaN materials have a polarization due to inversion asymmetry in the C direction (AlN materials have a polarization of 0.081C/cm)²The polarization intensity of the GaN material is 0.029C/cm²) Therefore, a large amount of residual polarization charges exist at the interface of AlGaN of different Al compositions. Potential wells for electrons and holes can be formed at the interface due to interface polarization charges in the multilayered AlGaN heterojunction structure to deplete the background carrier concentration in the heterojunction. In addition, the thicker composition of the single layer thickness and stress control in each period are easier in the multilayer heterojunction structure compared with the multiple quantum well structure. The high resistance buffer layer is prepared by utilizing the AlGaN heterojunction structure with multiple layers, and the high resistance is obtained by controlling the growth parameters of the MOCVD and introducing the energy level of metal impuritiesCompared with the GaN method, the method has no risk of heavy metal pollution to the reaction chamber, and can obtain the high-quality GaN-based buffer layer. The utility model has the advantages of it is following:

1. by growing a multilayer AlGaN heterojunction structure and utilizing a current carrier potential well formed by fixed polarization charges in a heterojunction interface space, the background electron concentration is exhausted, so that a GaN-based buffer layer with high resistance is obtained;

2. al components and thicknesses of all layers in the AlGaN heterojunction structure are designed to be used as a high-resistance stress transmission buffer layer for GaN epitaxial growth on a Si substrate and a high-resistance back barrier layer in a HEMT device structure;

3. by utilizing the stress change of an interface in the AlGaN heterojunction structure, the annihilation of threading dislocation can be promoted, and the crystal quality of the GaN of the silicon-based GaN epitaxial wafer is improved;

4. the scattering effect of the vertical direction of the current carrier is enhanced by using the interface scattering of the multi-layer AlGaN heterojunction structure, so that the drift length and the leakage under high voltage are reduced.

Drawings

Fig. 1 is a schematic structural diagram of the present invention;

fig. 2 is a first schematic diagram of the heterojunction structure of the present invention;

fig. 3 is a second schematic diagram of the heterojunction structure of the present invention;

fig. 4 is a schematic structural diagram of a first embodiment of the present invention;

fig. 5 is a graph of the vertical leakage curve of the first embodiment of the present invention;

fig. 6 is a schematic view of a second embodiment of the invention;

fig. 7 is a schematic view of a third embodiment of the present invention;

fig. 8 is a schematic view of a fourth embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The utility model discloses an AlGaN double-heterojunction high-resistance buffer layer epitaxial structure, as shown in figure 1, comprises a substrate 1, a nucleation layer 2 and an AlGaN double-heterojunction which are stacked from bottom to topJunction high-resistance buffer layer 3 and GaN layer 4: contain the heterojunction structure more than two in the two heterojunction high resistance buffer layer of AlGaN 3, wherein, including two-layer AlGaN layer in the heterojunction structure of every cycle the utility model discloses in, two-layer AlGaN layer is Al respectively_aGa_1-aN layer and Al_bGa_1-bAnd N layers. May be Al_aGa_1-aThe thickness range of the N layer is 100-1000nm, Al_bGa_1-bThe thickness of N layer is 1-99nm, and may be Al_aGa_1-aThe thickness range of the N layer is 1-99nm, Al_bGa_1-bThe thickness of the N layer is in the range of 100-1000 nm. Further, the number of the AlGaN double-heterojunction high-resistance buffer layers 3 is one or more, and can be selected according to a specific device structure.

In the utility model, the Al component range is 1% -99%. In the AlGaN heterojunction structure, because of the difference of Al components of the potential barrier and the potential well interface, the two interfaces form spatially fixed polarized charges, so that the background carrier concentrations of the potential barrier and the potential well layer are exhausted, and a buffer layer with high resistance is obtained. In addition, carrier scattering can be increased through the interface of the multilayer AlGaN double heterojunction, so that the leakage of the buffer layer is reduced, and the resistance of the buffer layer is increased.

As shown in fig. 2, the heterojunction structure is a heterojunction with a thin barrier (thin barrier means that the barrier thickness is smaller than the well thickness). Comprising said Al in a layered arrangement_aGa_1-aThe N layer is low Al component 3111 … … 31m1, the Al_bGa_1-bThe N layer is a high Al component 3112 … … 31m 2; al (Al)_aGa_1-aThe thickness range of the N layer is 100-1000nm, Al_bGa_1-bThe thickness of the N layer ranges from 1 nm to 99 nm. In the heterojunction structure of each period, Al which may be of low Al composition_aGa_1-aAl with high Al component laminated on N layer_aGa_1-aN layer, or Al with high Al component_aGa_1-aAl having a low Al content is laminated on the N layer_aGa_1-aAnd N layers.

As shown in fig. 3, the heterojunction structure is a heterojunction with a thin well (thin well means that the thickness of the well is less than the thickness of the barrier). Comprising said Al in a layered arrangement_aGa_1-aThe N layer is of high Al component3211 … … 32m1, Al_bGa_1-bThe N layer is low Al component 3212 … … 32m 2; al (Al)_aGa_1-aThe thickness range of the N layer is 1-99nm, Al_bGa_1-bThe thickness of the N layer is in the range of 100-1000 nm. Similarly, in the heterojunction structure of each period, Al having a high Al composition may be contained_aGa_1-aAl having a low Al content is laminated on the N layer_aGa_1-aN layer, or Al with low Al component_aGa_1-aAl with high Al component laminated on N layer_aGa_1-aAnd N layers.

As shown in FIG. 4, for the first embodiment of the present invention, a high-resistance GaN-based buffer layer is prepared on a silicon substrate by using a stress transfer layer containing a multi-layered AlGaN heterojunction structure, and its epitaxial structure comprises, from bottom to top, a substrate Si substrate 11, an AlN nucleation layer 21, and a high-resistance Al nucleation layer_aGa_1-aN/Al_bGa_1-bA multilayer AlGaN double heterojunction stress transfer layer 31 of N, a GaN layer 41.

(1) An AlN nucleation layer was grown using MOCVD on a 6 inch silicon substrate 1mm thick. And (3) desorbing at 1050 ℃ for 15min to remove oxides and impurities on the surface of the Si, so that the step-shaped surface appearance is exposed. Then growing a nucleation layer at a high temperature: the growth temperature is 1100 ℃, the TMAl flow is 250sccm, NH₃The flow rate is 3000sccm, the air pressure in the reaction chamber is 70mbar, the growth speed is about 0.3um/h, and the growth time is 40 min. The AlN nucleation layer has a thickness of about 200 nm.

(2) And (2) continuously growing a plurality of layers of AlGaN heterojunction structures on the AlN nucleating layer of the (1) by utilizing MOCVD (metal organic chemical vapor deposition), wherein the average Al composition of the first group of multi-layer heterojunction structures is about 74 percent, and the growth of Al comprises ① growth of Al with high Al composition_bGa_1-bThe growth conditions of the N layer are as follows: MO flow rate, wherein TMGa is 30sccm, TMAl is 510sccm, and NH is added₃The flow rate is 1500sccm (the Al component is 74.5%), the surface temperature is 1050 ℃, the growth time is 560s, the thickness is about 120nm, and ② grows Al with low Al component_aGa_1-aN layer, growth conditions are as follows: MO flow rate, wherein TMGa is 49sccm, TMAl is 402sccm, and NH is added₃The flow rate of (1) was 2000sccm (Al component: 60%); the surface temperature is 1050 ℃, the growth time is 23s, and the thickness is about 5 nm; repeatedly growing for 3 cycles① - ②, a multilayered AlGaN double heterojunction stress transfer layer with an average Al composition of 74% and a thickness of about 375nm was obtained.

(3) Continuously growing a multilayer AlGaN heterojunction structure with the average Al component of about 50 percent on the AlGaN double heterojunction layer with the average Al component of 74 percent in the step (2) by utilizing MOCVD (metal organic chemical vapor deposition) as a second group of multilayer double heterojunction stress transfer layers, wherein the growth of the second group of multilayer double heterojunction stress transfer layers comprises the step of ① growing Al with high Al component_bGa_1-bThe growth conditions of the N layer are as follows: MO flow rate, wherein TMGa is 56sccm, TMAl is 455sccm, and NH is added₃The flow rate is 1500sccm (Al component is 50.5%), the surface temperature is 1050 ℃, the growth time is 520s, the thickness is about 130nm, ② grows Al with low Al component_aGa_1-aN layer, growth conditions are as follows: MO flow rate, wherein TMGa is 85sccm, TMAl is 385sccm, and NH is added₃The flow rate of the AlGaN heterojunction structure is 2000sccm (the Al component is 35.5%), the surface temperature is 1050 ℃, the growth time is 20s, the thickness is about 5nm, and ① - ② with 8 periods are repeatedly grown to obtain the multilayer AlGaN heterojunction structure stress transfer layer with the thickness of about 1080nm and the average Al component of 50%.

(4) Continuously growing a multilayer AlGaN double heterojunction with the average Al component of about 25 percent on the multilayer AlGaN double heterojunction layer with the average Al component of 50 percent in the step (3) by utilizing MOCVD (metal organic chemical vapor deposition) as a stress transfer layer of a third group of multilayer AlGaN heterojunction structure, wherein the growth of the stress transfer layer of the third group of multilayer double heterojunction comprises the step of ① growing Al with high Al component_bGa_1-bThe growth conditions of the N layer are as follows: MO flow rate, wherein TMGa is 168sccm, TMAl is 450sccm, and NH is added₃The flow rate is 1500sccm (Al component is 25.5%), the surface temperature is 1050 ℃, the growth time is 250s, the thickness is about 145nm, and ② grows Al with low Al component_aGa_1-aN layer, growth conditions are as follows: MO flow rate, wherein TMGa is 250sccm, TMAl is 185sccm, and NH is added₃The flow rate of the AlGaN heterojunction structure is 2000sccm (the Al component is 10.5%), the surface temperature is 1050 ℃, the growth time is 10s, the thickness is about 5nm, and the multilayer AlGaN heterojunction structure stress transfer layer with the average Al component of about 1.5um is obtained by repeatedly growing ① - ② for 10 periods.

(5) A GaN layer grows on the stress transfer layer containing the multilayer AlGaN heterojunction structure41, a GaN layer grown at low temperature and low pressure, TMGa flow of 200sccm, and NH₃The flow rate of the growth medium is 12000sccm, the growth surface temperature is about 1000 ℃, the air pressure of the reaction chamber is 50mbar, the growth rate is about 2.5um/h, the growth time is 40min, and the thickness is about 1600 nm.

Vertical leakage results for GaN-based epitaxial layers grown according to the above structure as shown in fig. 5, the multilayer AlGaN heterojunction structure can reduce the background carrier concentration and increase the scattering of carriers, resulting in a high-resistance GaN-based buffer layer having a low leakage value (0.1 μ a/mm2@ 650V).

Further, the heterojunction structure further comprises an Al component increasing layer and/or an Al component decreasing layer positioned on the Al_aGa_1-aN layer and Al_bGa_1-bBetween the N layers. In this embodiment, the Al component increasing layer is Al_vGa_1-vThe N and Al component decreasing layer is Al_uGa_1-uN。

As shown in FIG. 6, in accordance with the second embodiment of the present invention, Al having a high Al content in the multi-layered AlGaN heterojunction structure_bGa_1-bN layer and Al of low Al composition_aGa_1-aThe interface of the N layer is in gradual transition. An Al component increasing layer and an Al component decreasing layer on Al_aGa_1-aN layer and Al_bGa_1-bBetween the N layers. The Al component gradually-increasing layer and the Al component gradually-decreasing layer are alternated mutually, and a layer of Al component gradually-increasing layer and a layer of Al component gradually-decreasing layer are used as a superposition period.

As shown in fig. 7 and 8, in the AlGaN heterojunction structure having a plurality of layers, to which the third and fourth embodiments of the present invention are applied, Al having a high Al composition_bGa_1-bN layer and Al of low Al composition_aGa_1-aThe interface of the N layer is an abrupt interface and a gradual interface.

Further, the nucleation layer 2 is specifically an AlN nucleation layer.

Further, the substrate 1 is specifically a sapphire substrate, a silicon carbide substrate, or a silicon substrate.

Further, the number of the heterojunction structure period is 2-100.

The utility model discloses use multilayer AlGaN heterojunction structure preparation high resistance gallium nitride buffer layer, can effectively reduce the buffer layer and leak current, simultaneously, thereby periodic stress in the AlGaN heterojunction structure can filter the crystal quality that pierces through dislocation improvement epitaxial material improves device high-pressure characteristic and reduces the useless consumption of device, is fit for the actual production and uses.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that all changes and modifications made according to the claims and the specification of the present invention should fall within the scope covered by the present invention.

Claims

1. An AlGaN double-heterojunction high-resistance buffer layer epitaxial structure is characterized in that: the GaN-based high-resistance substrate comprises a substrate, a nucleating layer, an AlGaN double-heterojunction high-resistance buffer layer and a GaN layer which are stacked from bottom to top: the AlGaN double-heterojunction high-resistance buffer layer comprises more than two heterojunction structures, wherein the heterojunction structure of each period comprises two AlGaN layers, and the thickness range of one layer is 100-1000 nm; the thickness of the other layer is in the range of 1-99 nm.

2. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the heterojunction structure is a heterojunction with a thin barrier.

3. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 2, wherein: two AlGaN layers are respectively Al_aGa_1-aN layer and Al_bGa_1-bN layer of said Al_aGa_1-aThe N layer is a low Al component layer, the Al_bGa_1-bThe N layer is a high Al component layer.

4. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the heterojunction structure is a heterojunction with a thin potential well.

5. According toThe epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer of claim 4, wherein: two AlGaN layers are respectively Al_aGa_1-aN layer and Al_bGa_1-bN layer of said Al_aGa_1-aThe N layer is a high Al component layer, and the Al_bGa_1-bThe N layer is a low Al component layer.

6. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the heterojunction structure further comprises an Al component increasing layer and/or an Al component decreasing layer which are positioned between the two AlGaN layers.

7. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the number of the AlGaN double-heterojunction high-resistance buffer layers is one or more.

8. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the number of the heterojunction structure periods is 2-100.

9. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the nucleation layer is specifically an AlN nucleation layer.

10. The epitaxial structure of AlGaN double-heterojunction high-resistance buffer layer according to claim 1, wherein: the substrate is specifically a sapphire substrate, a silicon carbide substrate or a silicon substrate.