Abstract:The remote epitaxy of GaN via graphene has attracted
much attention
due to the potential of easy mechanical exfoliation, and the exfoliated
layers can be transferred onto foreign substrates according to the
application needs, which is beneficial to improve the performance
of GaN-based devices. In this work, a GaN epi-layer was grown by metal–organic
chemical vapor deposition on the monolayer-graphene-coated AlN/sapphire
or GaN substrates. The influence of growth temperature, carrier gas,
and substrate on the e… Show more
“…We note that metal atoms such as Al, Ga, and In do not lead to carbon-loss, reported in the following studies [ 178 , 182 , 227 ]. Similar results for graphene loss on III-nitride substrate have been reported elsewhere [ 40 , 205 , 228 ]. Fig.…”
Section: Interaction Between Growth Technique 2d Material and Substra...supporting
confidence: 89%
“…Aluminum Nitride (AlN) is a material with a wurtzite structure and a lattice mismatch of ~ 2.4% with GaN. The polarity of AlN substrates is rather advantageous for improving the crystal quality of GaN growth, and is another good candidate for remote epitaxy [ 40 , 200 – 205 ]. Zhang et al succeeded in high-quality GaN growth, including low-threading dislocation through the modulation of graphene surface states by transferring graphene on sputtered AlN templates [ 200 ].…”
Section: Interaction Between Growth Technique 2d Material and Substra...mentioning
Remote epitaxy, which was discovered and reported in 2017, has seen a surge of interest in recent years. Although the technology seemed to be difficult to reproduce by other labs at first, remote epitaxy has come a long way and many groups are able to consistently reproduce the results with a wide range of material systems including III-V, III-N, wide band-gap semiconductors, complex-oxides, and even elementary semiconductors such as Ge. As with any nascent technology, there are critical parameters which must be carefully studied and understood to allow wide-spread adoption of the new technology. For remote epitaxy, the critical parameters are the (1) quality of two-dimensional (2D) materials, (2) transfer or growth of 2D materials on the substrate, (3) epitaxial growth method and condition. In this review, we will give an in-depth overview of the different types of 2D materials used for remote epitaxy reported thus far, and the importance of the growth and transfer method used for the 2D materials. Then, we will introduce the various growth methods for remote epitaxy and highlight the important points in growth condition for each growth method that enables successful epitaxial growth on 2D-coated single-crystalline substrates. We hope this review will give a focused overview of the 2D-material and substrate interaction at the sample preparation stage for remote epitaxy and during growth, which have not been covered in any other review to date.
Graphical Abstract
“…We note that metal atoms such as Al, Ga, and In do not lead to carbon-loss, reported in the following studies [ 178 , 182 , 227 ]. Similar results for graphene loss on III-nitride substrate have been reported elsewhere [ 40 , 205 , 228 ]. Fig.…”
Section: Interaction Between Growth Technique 2d Material and Substra...supporting
confidence: 89%
“…Aluminum Nitride (AlN) is a material with a wurtzite structure and a lattice mismatch of ~ 2.4% with GaN. The polarity of AlN substrates is rather advantageous for improving the crystal quality of GaN growth, and is another good candidate for remote epitaxy [ 40 , 200 – 205 ]. Zhang et al succeeded in high-quality GaN growth, including low-threading dislocation through the modulation of graphene surface states by transferring graphene on sputtered AlN templates [ 200 ].…”
Section: Interaction Between Growth Technique 2d Material and Substra...mentioning
Remote epitaxy, which was discovered and reported in 2017, has seen a surge of interest in recent years. Although the technology seemed to be difficult to reproduce by other labs at first, remote epitaxy has come a long way and many groups are able to consistently reproduce the results with a wide range of material systems including III-V, III-N, wide band-gap semiconductors, complex-oxides, and even elementary semiconductors such as Ge. As with any nascent technology, there are critical parameters which must be carefully studied and understood to allow wide-spread adoption of the new technology. For remote epitaxy, the critical parameters are the (1) quality of two-dimensional (2D) materials, (2) transfer or growth of 2D materials on the substrate, (3) epitaxial growth method and condition. In this review, we will give an in-depth overview of the different types of 2D materials used for remote epitaxy reported thus far, and the importance of the growth and transfer method used for the 2D materials. Then, we will introduce the various growth methods for remote epitaxy and highlight the important points in growth condition for each growth method that enables successful epitaxial growth on 2D-coated single-crystalline substrates. We hope this review will give a focused overview of the 2D-material and substrate interaction at the sample preparation stage for remote epitaxy and during growth, which have not been covered in any other review to date.
Graphical Abstract
“…This process is no longer remote epitaxy but a special kind of epitaxial lateral overgrowth (ELOG) (41). As previously reported (17,25,(42)(43)(44)(45), remote epitaxy is a promising method for fabricating transferable III-nitride films and light-emitting devices. Remote epitaxy of single-crystal GaN(0001) films on graphene/GaN(0001) templates has been reported at a growth temperature of ~700°C by MBE (18,24).…”
Transferred graphene provides a promising III-nitride semiconductor epitaxial platform for fabricating multifunctional devices beyond the limitation of conventional substrates. Despite its tremendous fundamental and technological importance, it remains an open question on which kind of epitaxy is preferred for single-crystal III-nitrides. Popular answers to this include the remote epitaxy where the III-nitride/graphene interface is coupled by nonchemical bonds, and the quasi-van der Waals epitaxy (quasi-vdWe) where the interface is mainly coupled by covalent bonds. Here, we show the preferred one on wet-transferred graphene is quasi-vdWe. Using aluminum nitride (AlN), a strong polar III-nitride, as an example, we demonstrate that the remote interaction from the graphene/AlN template can inhibit out-of-plane lattice inversion other than in-plane lattice twist of the nuclei, resulting in a polycrystalline AlN film. In contrast, quasi-vdWe always leads to single-crystal film. By answering this long-standing controversy, this work could facilitate the development of III-nitride semiconductor devices on two-dimensional materials such as graphene.
“…Since the 1970s, Olsen et al proposed that wide-bandgap semiconductors have high energy conversion efficiency . Researchers subsequently developed a series of wide band gap semiconductors: gallium nitride (GaN), silicon carbide (SiC), zinc oxide (ZnO), titanium dioxide (TiO 2 ), and diamond . Among wide-bandgap semiconductors of wide interest, ZnO has attracted particular attention because of high radiation tolerance, excellent chemical stability, low cost, and environmental friendliness. , Moreover, ZnO exhibits a high exciton binding energy (60 meV), a high breakdown strength, and much higher electron mobility than titanium oxide (TiO 2 ) (155 cm 2 ·V –1 ·s –1 vs 10 –5 cm 2 ·V –1 ·s –1 ), which would be favorable for electron transmission. , Among the many forms of ZnO, one-dimensional (1-D) ZnO nanofibers with the surface effect and the quantum-size effect have a large specific surface area and 1-D charge transport .…”
Betavoltaic batteries, as a kind of ultimate battery, have attracted much attention. ZnO is a promising wide-bandgap semiconductor material that has great potential in solar cells, photodetectors, and photocatalysis. In this study, rare-earth (Ce, Sm, and Y)-doped ZnO nanofibers were synthesized using advanced electrospinning technology. The structure and properties of the synthesized materials were tested and analyzed. As betavoltaic battery energy conversion materials, the results show that rare-earth doping increases the UV absorbance and the specific surface area and slightly reduces the band gap. In terms of electrical performance, a deep UV (254 nm) and X-ray source (10 keV) were used to simulate a radioisotope β-source to evaluate the basic electrical properties. Among them, the output current density of Y-doped ZnO nanofibers can reach 87 nA•cm −2 , which is 78% higher than that of traditional ZnO nanofibers, by deep UV. Besides, the photocurrent response of Y-doped ZnO nanofibers is superior to that of Ce-doped and Sm-doped ZnO nanofibers by soft X-ray. This study provides a basis for rare-earthdoped ZnO nanofibers as energy conversion devices used in betavoltaic isotope batteries.
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