Graphene-driven strain engineering enables strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode

Graphene-driven strain engineering enables strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode

(a) FWHMs XRCs of AlN epilayer with different thicknesses grown on Gr-buffered sapphire. (b) Estimated DD of AlN films with Gr barrier layer with different thicknesses. (c) DF images of the epitaxial AlN / Gr / sapphire with g = [0002]. (d) The HRTEM image of the AlN / Gr / sapphire cell. (e) Raman spectra of as-grown AlN / Gr / sapphire structure. (f) Raman ratio of E₂ (height) of AlN with different growth thicknesses. Yes: Hongliang Chang et al.

The exact range of AlN components makes them suitable for the production of DUV optoelectronic devices, a wide range of applications in the fields of treatment, water and air disinfection, medicine and biochemistry. Therefore, the availability of a high epitaxy of AlN films is very important to ensure the efficient performance of DUV films.

Currently, due to the lack of cost -effective homogeneous substrates, the best option to grow AlN films is the one that usually performs heteroepitaxial growth in sapphire. Unfortunately, the different concentrations between AlN and the sapphire substrate introduce crystalline imperfections in the AlN epilayer. Importantly, the bulk of the AlN film leads to nonuniformity of the Al distribution in the upper AlGaN layer combined with the resistance of the wafer, which limits the performance of the material. do. Therefore, a suitable design is required to make a qualitative leap to detect the high growth of AlN heteroepitaxial films and to meet the application requirements of optoelectronic DUV devices.

In recent years, an existing pathway called quasi-van der Waals (QvdW) epitaxy or distance epitaxy involving two-dimensional (2D) materials has been considered for high heteroepitaxial growth. of group-III nitrides. As a highly studied 2D material, graphene has been added as a barrier for the epitaxial growth of nitrides to effectively eliminate lattice mismatch and thermal mismatch between the epilayer and with a substrate. Preliminary reports of epitaxial nitride films on graphene have generally demonstrated the relaxation of the epitaxial system observed through the weak bond between graphene and the epilayers, but there is a lack of detailed discussion. confirmation of this statement.

Today, Dou et al. He observed the formation of a chemical bond at the center between straight-growing graphene and sapphire by aberration-corrected transmission electron microscopy and found a strong bond between graphene and sapphire, where which does not reverse the traditional knowledge of the breakdown through the weak vdW relationship between the graphene and the substrate. . Therefore, the QvdW epitaxy machine of AlN films needs to be re -engineered on graphene, which is important to accurately adjust the quality of AlN films and further enhance the performance of DUV optoelectronic films.

In a new paper published on Simple & Easy Science, a scientific team, led by Professor Tongbo Wei from the Research and Development Center for Semiconductor Lighting Technology, Institute of Semiconductors, Chinese Academy of Science, Beijing, China, and colleagues have successfully implemented a high -performance AlN film. through Gr-drive strain-pre-store engineering and demonstrates a unique method of strain relief in QvdW epitaxy. However, the free AlN film grown on graphene / sapphire can be used as a reliable benchmark for the high epitaxy of DUV-LED materials.

Graphene-driven strain engineering enables strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode

(a) Graphical analysis of the coalescence between two AlN nanowires and the length of the surface. (b) Stretch analysis of the association between two infinite AlN surfaces and the upward contact lengths. d // (Al-N) the relative length of the Al-N bond formed by the skin Al and N forces relative to the skin, d // (Al) the relative length of the Al- bond N is formed by the surface Al and the bottom N atom, and d // (N) is the relative length of the Al-N bond formed by the surface N and the bottom Al. The assumptions are the same for perpendicular holds. The air and c subscripts show the nanowire holders at the edge and near the edge. (c) The conversion of the corresponding lengths of the nanowire and the infinite surface as a function of the separation. (d) Transformation of the relative lengths of nanowire and infinite surfaces as a result of separation. Yes: Hongliang Chang et al.

They summarize the main points of their study as follows:

“The dislocation density of AlN epilayer with graphene indicates a similar pattern to sawtooth-like evolution during the QvdW epitaxy process and has much lower properties than that of sapphire. Thickness.

“The calculation of the first factors is included to explain how graphene regulates the nature of the AlN film. lattice and thermal mismatch during heteroepitaxy, thus yielding an AlN film without the process.

“The wide map of the DUV-LED made of a weak compressive filter shows the 1.8 μm n-AlGaN layer, presenting the AlN film as a reliable template layer that can be used. high crystalline surface of the surface.LED epitaxial design.

“The 283 nm DUV LED with graphene displays 2.1 times higher light output power compared to its counterpart in sapphire and excellent stability of light wavelength below a certain level. current from 10 mA to 80 mA, which is considered a good crystal quality.with a weak balance of epitaxial activity due to graphene.

“This work demonstrates the internal performance of QvdW nitride growth to improve epitaxial efficiency on highly-mismatched substrates and undoubtedly sheds light on the re-emergence of the production of nitride. nitride. ”

Graphene crystals are better under a copper coating

More information:
Hongliang Chang et al, Graphene-driving strain engineering enables strain-free epitaxy of AlN film for deep ultraviolet light-emitting diode, Basics: science and applications (2022). DOI: 10.1038 / s41377-022-00756-1

Presented by Changchun Institute of Optics

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