CN214797333U

CN214797333U - Substrate for growing gallium nitride on graphene mask

Info

Publication number: CN214797333U
Application number: CN202120651499.8U
Authority: CN
Inventors: 陈王义博; 曹冰; 徐立跃; 李路; 杨帆
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2021-11-19
Anticipated expiration: 2031-03-31

Abstract

The utility model discloses a substrate for growing gallium nitride by a graphene mask, which comprises a basal layer and a graphene mask layer, wherein the graphene mask layer is deposited on the basal layer; the graphene mask layer is etched with a grating-shaped stripe structure, the groove portion of the grating-shaped stripe structure is a window area for growing a gallium nitride layer, and the protruding portion of the grating-shaped stripe structure is a mask area. The utility model has the advantages that: the graphene mask layer structure can effectively reduce gallium nitride dislocation and improve the growth quality of the gallium nitride dislocation; because the graphene mask layer is decomposed and disappears in the growth process, the stress and small-angle grain boundary defects brought to gallium nitride by the mask are reduced. The structure can also be applied to III-V compound semiconductors other than gallium nitride.

Description

Substrate for growing gallium nitride on graphene mask

Technical Field

The utility model relates to the technical field of semiconductors, specifically a substrate of growth gallium nitride.

Background

The group III nitride semiconductor taking gallium nitride (GaN) as a research hotspot has excellent photoelectric performance and wide adjustable band gap, and has great advantages and application prospects in the fields of illumination display, high-frequency and high-power electronic devices, optical storage, communication, energy sources and the like. High performance semiconductor devices rely on high quality semiconductor wafers. Currently, the main problems of gallium nitride are high dislocation density and stress, which greatly affect the crystal quality of gallium nitride and degrade the performance of the device. In the traditional gallium nitride epitaxial growth process, the lateral epitaxial technology is a method for effectively reducing dislocation and improving the crystal. In recent years, a series of two-dimensional materials such as graphene provides a new idea for growth and preparation of gallium nitride. Due to the fact that the surface of the graphene two-dimensional material is lack of dangling bonds, the gallium nitride is difficult to nucleate on the surface of the graphene, and the graphene can be used as a mask layer to laterally extend the gallium nitride. Due to the fact that the thickness of the graphene is extremely thin, the defect of a small-angle grain boundary brought to gallium nitride by a conventional mask in the growth process can be effectively reduced.

Since Shaw et al succeeded in growing anisotropic gallium arsenide (GaAs) single crystals with some reduction in crystal defects, the lateral epitaxy technique became an effective dislocation reduction method (see [ Shaw, Don W. Selective epitaxial deposition of gallium arsenic in holes [ J ]. Journal of the Electrochemical Society, 1966, 113(9):904-908 ]). Pierre Gibart et al summarize various lateral epitaxy techniques, and these improved lateral epitaxy techniques have been used to reduce dislocations and the effect of the mask on GaN by changing the type and growth of the mask (see [ Pierre, Gibart. Metal organic phase epitaxy of GaN and lateral epitaxy [ J ]. Reports on growth in Physics, 2004, 67(5):667 ]). Although the commonly used mask layer material can also play a certain role in improving the quality of the gallium nitride, the commonly used mask layer material serving as a mask structure of a three-dimensional material cannot avoid the defect of low-angle grain boundaries.

SUMMERY OF THE UTILITY MODEL

The technical problem solved by the utility model is the problem of stress and dislocation brought by the commonly used heterogeneous mask in the lateral extension of GaN.

The following technical scheme is provided:

a substrate for growing gallium nitride on a graphene mask comprises a base layer and a graphene mask layer, wherein the graphene mask layer is deposited on the base layer; the graphene mask layer is etched with a grating-shaped stripe structure, the groove portion of the grating-shaped stripe structure is a window area for growing a gallium nitride layer, and the protruding portion of the grating-shaped stripe structure is a mask area.

Forming a groove part in the etched area on the graphene mask layer, wherein the depth of the groove is up to the surface of the substrate layer; the groove part of the grating-shaped stripe structure is a window area for growing the gallium nitride layer, and the protrusion part of the grating-shaped stripe structure is a mask area.

Preferably, the base layer is a sapphire-based gallium nitride.

Preferably, the thickness of the graphene mask layer is about 3nm, and the number of layers is about 8-10.

Preferably, the width of the window area of the grating-like stripe structure is 3 μm, the width of the mask area is 7 μm, and the period is 10 μm, and the stripe width and period can be adjusted appropriately for different growth methods.

Preferably, the gallium nitride layer directly nucleates and grows on the substrate layer through a graphene mask layer window area, the graphene mask layer disappears in the growing process, dislocation extension below the mask area is still blocked, and the gallium nitride keeps a lateral epitaxial growth mode. The reason is that at the first-step growth temperature, graphene is decomposed slowly, meanwhile, gallium nitride has good lateral epitaxial growth capacity, and the gallium nitride grown in the window area can grow laterally to the position above the mask area and combined to form a film by adjusting growth parameters.

Advantageous effects

The utility model provides a substrate of graphite alkene mask growth gallium nitride utilizes the graphite alkene surface to hang the few characteristics of key, is applied to graphite alkene in the mask structure. Due to the lateral epitaxial growth capability of the gallium nitride, the structure has good effects of reducing dislocation of the gallium nitride and improving the quality of gallium nitride crystals. The defect introduced by the mask layer is greatly reduced by utilizing the characteristic that graphene disappears in the growth process, so that the performance of the gallium nitride material is improved.

According to the technical scheme, only the substrate layer and the gallium nitride layer are left after the growth is completed, and compared with the commonly used technology for growing the gallium nitride by lateral epitaxy through a mask method, heterogeneous materials are not left under the gallium nitride layer. The growth structure reduces stress and corresponding dislocation caused by the difference of the thermal expansion coefficients of the mask material and the gallium nitride in the growth process, and improves the performance of a device manufactured by the subsequent gallium nitride. The graphene mask layer can keep a lateral epitaxial growth mode by adjusting the proper growth temperature, and meanwhile, the graphene mask layer gradually disappears and is not kept between the substrate and the gallium nitride in the growth process, so that the problems of stress and dislocation brought to the gallium nitride layer by the mask layer in the lateral epitaxial technology are greatly reduced.

Drawings

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

fig. 2 is an electron microscope image of the substrate covered by the graphene mask of the present invention;

FIG. 3 is an electron microscope image of the surface of gallium nitride after the first step of growth;

FIG. 4 is an electron microscope image of the surface of gallium nitride after the first step of growth;

fig. 5 is a raman chart of graphene after the first step of growth of the present invention;

FIG. 6 is an electron microscope image of gallium nitride after the growth of the present invention is completed;

FIG. 7 is a CL diagram after growing a gallium nitride layer according to the present invention;

fig. 8 is a graph of the present invention plotted against raman characterization of cross-sectional stress of gallium nitride after growth according to the first step;

fig. 9 is a raman diagram of the surface stress characterization of gallium nitride after the growth of the present invention is completed.

Reference numerals

The structure comprises a 1-gallium nitride layer, a 2-graphene mask layer, a 3-substrate layer and a 4-grating-shaped stripe structure.

Detailed Description

The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

Examples

As shown in fig. 1, a substrate for growing gallium nitride on a graphene mask includes a base layer 3 and a graphene mask layer 2, where the graphene mask layer is deposited on the base layer; the graphene mask layer is etched with a grating-shaped stripe structure 4, the groove part of the grating-shaped stripe structure is a window area for growing a gallium nitride layer, and the protruding part of the grating-shaped stripe structure is a mask area.

When the substrate of the technical scheme is used, the gallium nitride layer 1 is grown by a metal organic chemical vapor deposition method, and a two-step method is adopted, wherein the growth temperature of the first step is 970 ℃, and the growth temperature of the second step is 1030 ℃. Fig. 2 is a light mirror image of the graphene mask layer after etching, and the graphene forms a grating-like stripe structure according to an expected period after etching by oxygen plasma. Fig. 3 is a surface electron microscope image of gan grown at 970 ℃ in the first growth step, and it can be seen that the gan forms a striped structure which is not merged, which is a typical lateral epitaxial growth mode. Fig. 4 is a sectional electron microscope image of gallium nitride grown at a first growth temperature of 970 c, and it can be seen that the stripe structure of gallium nitride is well formed. Fig. 5 is a raman test chart of the mask region of the graphene mask layer after the first step growth is completed, and characteristic peaks at three wavelengths of 1350, 1580, and 2700 without graphene can be seen. FIG. 6 is an electron micrograph of gallium nitride grown after the first growth step and continued at a growth temperature of 1030 deg.C. Fig. 7 is a CL diagram after the second step of growth, where the dark dots represent dislocations, which can be seen to exhibit a periodic arrangement, which also corresponds to the typical growth characteristics of gallium nitride lateral epitaxy. FIG. 8 shows a mask layer after a first growth stepAnd (3) representing the stress of the cross section (white line position in an inset) of the upper gallium nitride layer, wherein the stress of the gallium nitride can be calculated by the following formula:

wherein

Represents gallium nitride E₂Shift of peak position from 568nm wavelength. As can be seen from the figure, the stress at the cross section is consistent for the sample using the graphene mask, because the stress caused by the difference of the thermal expansion coefficient between the graphene mask and the gallium nitride is almost eliminated due to the gradual disappearance of the graphene mask in the growth process. Fig. 9 is a stress characterization for gallium nitride after growth is completed, and it can be seen that the stress is significantly reduced compared to the original substrate for the sample using the graphene mask.

The utility model discloses the excellent performance of graphite alkene has mainly been utilized. Because the surface dangling bonds of the graphene are few, the gallium nitride is difficult to nucleate on the surface of the graphene, the graphene is applied to a mask layer for gallium nitride growth, the gallium nitride only can directly nucleate and grow on a substrate through a window area of the mask, the gallium nitride does not grow on the graphene mask, the lateral epitaxy capability of the gallium nitride enables the gallium nitride to be combined and formed into a film even if the gallium nitride nucleates at a window in a subsequent growth process, therefore, the dislocation of the substrate layer 3 can be blocked by the mask layer, only the dislocation at the window can continue to extend into the gallium nitride layer 1, and the effect of reducing the dislocation of the gallium nitride is achieved. In the high-temperature growth process, the graphene mask layer is gradually decomposed and disappears and is not finally kept in a sample after the growth is finished, so that the difference between the common mask material and the gallium nitride layer in terms of volume, thermal expansion coefficient and the like is avoided, and the dislocation and stress brought by the mask layer are greatly reduced. The utility model discloses in, because graphite alkene directly grows on stratum basale 3 through plasma enhanced chemical vapor deposition method, avoided transferring the pollution that graphite alkene in-process brought usually. The structure 4 grating-shaped stripe structure is manufactured on the graphene mask layer by a photoetching-etching method, the graphene is etched by adopting oxygen plasma, the etching time is greatly shortened compared with the formation of the stripes of a common mask material, and therefore, the film can be selectively skipped during the photoetching process, the subsequent photoresist removal is easier and more thorough, the process is integrally simplified, the etching rate of a common substrate is low, and the base layer is protected.

The utility model discloses utilize the mask structure of graphite alkene to realize reducing growth gallium nitride dislocation, utilize graphite alkene can decompose the characteristic that disappears at the growth in-process simultaneously, further optimize the epitaxial technique of side direction, reduce gallium nitride's stress and dislocation. Therefore the utility model provides a graphite alkene mask structural design for improving gallium nitride growth quality has advantages such as can effectively reduce gallium nitride dislocation, stress and preparation high performance device, has huge application scene in the semiconductor trade.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the content of the present invention within the protection scope of the present invention.

Claims

1. The utility model provides a substrate of graphite alkene mask growth gallium nitride, includes stratum basale and graphite alkene mask layer, its characterized in that: the graphene mask layer is deposited on the substrate layer; the graphene mask layer is etched with a grating-shaped stripe structure, the groove portion of the grating-shaped stripe structure is a window area for growing a gallium nitride layer, and the protruding portion of the grating-shaped stripe structure is a mask area.

2. The substrate for growing gallium nitride on the graphene mask according to claim 1, wherein: the thickness of the graphene mask layer is 3nm, and the number of layers is 8-10.

3. The substrate for growing gallium nitride on the graphene mask according to claim 1, wherein: the width of the grating-shaped stripe structure window area is 3 mu m, the width of the mask area is 7 mu m, and the period is 10 mu m.