Faculty Profiles - AMANO, Hiroshi

Papers - AMANO, Hiroshi

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Metastable atomic-ordered configurations for Al<sub>1/2</sub>Ga<sub>1/2</sub>N predicted by Monte-Carlo method based on first-principles calculations

Gueriba, JS; Mizuseki, H; Cadatal-Raduban, M; Sarukura, N; Kawazoe, Y; Nagasawa, Y; Hirano, A; Amano, H

JOURNAL OF PHYSICS-CONDENSED MATTER Vol. 36 ( 13 ) 2024.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics Condensed Matter

Metastability of Aln/12Ga1−n/12N (n = 2–10: integer) with the 1–2 monolayer (ML) in-plane configuration towards the c [0001] direction has been demonstrated recently. To theoretically explain the existence of these metastable structures, relatively large calculation cells are needed. However, previous calculations were limited to the use of small calculation cell sizes to estimate the local potential depth (∆σ) of ordered Al1/2Ga1/2N models. In this work, we were able to evaluate large calculation cells based on the interaction energies between proximate Al atoms (δEAl–Al) in AlGaN alloys. To do this, δEAl–Al values were estimated by first-principles calculations (FPCs) using a (5a1 × 5a2 × 5c) cell. Next, a survey of the possible ordered configurations using various large calculation cell models was performed using the estimated δEAl–Al values and the Monte-Carlo method. Then, various ∆σ values were estimated by FPCs and compared with the configurations previously reported by other research groups. We found that the ordered configuration obtained from the (4a1 × 2a2 × 1c) calculation cell (C42) has the lowest ∆σ of −9.3 meV/cation and exhibited an in-plane configuration at the c(0001) plane having (–Al–Al–Ga–Ga–) and (–Al–Ga–) sequence arrangements observed along the m{11̄00} planes. Hence, we found consistencies between the morphology obtained from experiment and the shape of the primitive cell based on our numerical calculations.

DOI： 10.1088/1361-648X/ad1137

Study on Degradation of Deep-Ultraviolet Laser Diode

Zhang, ZY; Yoshikawa, A; Kushimoto, M; Sasaoka, C; Amano, H

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (A) Applications and Materials Science

The degradation of an AlGaN-based deep-ultraviolet laser diode during operation is studied. A rapid increase in threshold current without any facet mirror damage under direct current stress below the threshold current is observed, which is considered to limit the lifetime of continuous wave lasing to the level of seconds. The evolution of current–light and current–voltage characteristics suggests that the dominant mechanism of degradation is the increased loss of carriers before they can reach the active layer, i.e., the decrease in carrier injection efficiency. The decrease in emission intensity, which is more pronounced at lower current densities, and subsequent increase in sub-threshold current indicate the increase in defect density under current stress, which is similar to the well-analyzed degradation mechanism found in AlGaN-based light-emitting diodes.

DOI： 10.1002/pssa.202300946

Impacts of off-angle and off-direction on surface morphology of GaN grown by metalorganic vapor phase epitaxy on (0001) GaN substrate

Watanabe, H; Nitta, S; Ando, Y; Ohnishi, K; Honda, Y; Amano, H

JOURNAL OF CRYSTAL GROWTH Vol. 628 2024.2

Sn-doped n-type GaN layer with high electron density of 1020 cm-3 grown by halide vapor phase epitaxy

Hamasaki, K; Ohnishi, K; Nitta, S; Fujimoto, N; Watanabe, H; Honda, Y; Amano, H

JOURNAL OF CRYSTAL GROWTH Vol. 628 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Crystal Growth

A Sn-doped n-type GaN layer with a high electron density of 2 × 1020 cm−3 and a low resistivity of 8.7 × 10−4 Ω∙cm was grown by halide vapor phase epitaxy (HVPE). Sn doping was performed through the reaction between Sn metal and HCl gas. The Sn concentration markedly increased with decreasing growth temperature and the activation energy of Sn desorption from the GaN surface was found to be 4.1 eV. Smooth surfaces were obtained by introducing the Sn precursor even though the samples were grown at a low temperature of 905 °C, suggesting that Sn atoms act as surfactants and promote the migration of Ga adatoms. Almost all the Sn atoms act as donors in GaN below the Sn concentration of 2 × 1020 cm−3. These results indicate that using the Sn donor is promising for fabricating low-resistivity n-type GaN substrates by HVPE.

DOI： 10.1016/j.jcrysgro.2023.127529

Impact of unintentionally formed compositionally graded layer on carrier injection efficiency in AlGaN-based deep-ultraviolet laser diodes

Zhang Z., Yoshikawa A., Kushimoto M., Aoto K., Sasaoka C., Amano H.

Applied Physics Letters Vol. 124 ( 6 ) 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

Increasing the injection efficiency, a critical factor constraining the reduction in threshold current in AlGaN-based deep-ultraviolet laser diodes, represents one of the paramount remaining technical challenges. In this study, the impact of compositionally graded layers that were unintentionally formed at the interface between the p-cladding and the core layer on carrier injection efficiency was analyzed. Experimental evaluations using laser diodes have shown that the elimination of an unintentionally formed layer increases the injection efficiency above the threshold current, from the conventional 3% to 13%. It has been postulated that the electron overflow toward the p-side exerts a substantial deleterious effect on the injection efficiency. An improvement in this aspect is achieved by increasing the electron-blocking capability due to the improved interface abruptness between the p-cladding layer and the core layer. The lasing threshold was strongly reduced, and characteristic temperature increased from 76 to 107 K for the improved devices.

DOI： 10.1063/5.0184543

Optical activation of praseodymium ions implanted in gallium nitride after ultra-high pressure annealing

Ito, S; Sato, S; Bockowski, M; Deki, M; Watanabe, H; Nitta, S; Honda, Y; Amano, H; Yoshida, K; Minagawa, H; Hagura, N

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Vol. 547 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Lanthanide (Ln)-implanted gallium nitride (GaN) semiconductors have a variety of potential applications as light-emitting devices and quantum light sources, but their optical properties are not well understood. In this study, we investigate the room temperature optical properties of praseodymium (Pr) ion implanted single-crystal GaN and their changes upon ultrahigh pressure annealing (UHPA) up to 1480 °C. Photoluminescence (PL) spectra, luminescence transition lifetime, and excitation cross section of the implanted Pr ions are analyzed. In addition, the recovery of implantation-induced damage and the thermal diffusion of implanted Pr ions by UHPA are investigated by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry. The results show that the implantation damage is recovered by annealing at temperatures above 1200 °C, but Pr ions thermally diffuse to the surface as the annealing temperature increases. The annealing temperature at which a maximum PL intensity is obtained increases with increasing the implantation dose. However, the PL intensity decreases in all cases after annealing at 1480 °C, indicating that a quenching factor is dominant in this temperature range.

DOI： 10.1016/j.nimb.2023.165181

Impurity reduction in lightly doped <i>n</i>-type gallium nitride layer grown via halogen-free vapor-phase epitaxy

Kimura, T; Shimazu, H; Kataoka, K; Itoh, K; Narita, T; Uedono, A; Tokuda, Y; Tanaka, D; Nitta, S; Amano, H; Nakamura, D

APPLIED PHYSICS LETTERS Vol. 124 ( 5 ) 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

The development of gallium nitride (GaN) vertical-type metal-oxide-semiconductor field-effect transistors and p-i-n diode devices has gathered increasing attention. These devices require an n-type drift layer with a low doping level of 1016 cm−3 or less, minimized point defects inhibiting electron conduction, and a layer approximately 10 μm thick. Therefore, a practical method with a growth rate of at least several tens of μm/h and impurity concentrations of less than 1015 cm−3, except for that of dopants, is necessary. Halogen-free vapor-phase epitaxy (HF-VPE) has a high growth rate suitable for fabricating thick drift layers and utilizes a simple reaction between Ga vapor and ammonia gas (without a corrosive halogen gas), resulting in lower impurity levels. Herein, we eliminated the quartz content from the high-temperature zone to reduce the excess unintentional Si doping and identified that the nitrile gloves used for the growth preparation are other impurity contamination sources. We obtained a lightly n-type ([Si]=∼1016 cm−3) GaN layer, in which C, O, B, Fe, Mg, Al, Ca, Cr, Zn, Ni, Mn, and Ti impurity contents were below the detection limits of secondary ion mass spectrometry. Deep-level transient spectroscopy revealed that electron traps at EC − 0.26 and at EC − 0.59 eV were 2.7 × 1013 and 5.2 × 1014 cm−3, respectively. Moreover, the Hall effect analysis showed the acceptor-type defect-compensating donor content as approximately 2.7 × 1015 cm−3, resulting in a high electron mobility of HF-VPE GaN in the 30-710 K temperature range. Furthermore, we identified the Ca impurity as a deep acceptor, another killer defect leading to mobility collapse.

DOI： 10.1063/5.0191774

Droop and light extraction of InGaN-based red micro-light-emitting diodes

Park, JH; Pristovsek, M; Cai, WT; Kumabe, T; Choi, SY; Lee, DS; Seong, TY; Amano, H

SEMICONDUCTOR SCIENCE AND TECHNOLOGY Vol. 39 ( 1 ) 2024.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Semiconductor Science and Technology

In this letter, we investigate the impact of periphery, width, length and area on the external quantum efficiency (EQE) of stripe-type InGaN-based red micro-light-emitting diodes (µLEDs). A longer periphery resulted in a higher light extraction efficiency ( η e ) via the sidewall regardless of the area of the µLEDs. However, as the injection current increased a somewhat larger efficiency droop was observed at the longer periphery due to current crowding. Additionally, larger µLEDs experienced more self-heating than smaller ones, resulting in a red shift of wavelengths and a larger efficiency droop. When the current density exceeded 100 A cm−2, the EQE ratio of smaller-area μLEDs to larger-area ones increased significantly due to the difference in efficiency droop. Besides, a short light propagation length and a long emission width yielded a higher η e . Hence, the periphery, width, length and area of the µLEDs determine EQE, which provides insight into the pixel design of µLED displays.

DOI： 10.1088/1361-6641/ad0b88

Demonstration of AlGaN-on-AlN p-n Diodes With Dopant-Free Distributed Polarization Doping

Kumabe T., Yoshikawa A., Kawasaki S., Kushimoto M., Honda Y., Arai M., Suda J., Amano H.

IEEE Transactions on Electron Devices 2024

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Electron Devices

Nearly ideal vertical Al<inline-formula> <tex-math notation="LaTeX">$_{\textit{x}}$</tex-math> </inline-formula>Ga<inline-formula> <tex-math notation="LaTeX">$_{\text{1}-\textit{x}}$</tex-math> </inline-formula>N (<inline-formula> <tex-math notation="LaTeX">$\text{0.7} \leq \textit{x} < \text{1.0}$</tex-math> </inline-formula>) p-n diodes are fabricated on an aluminum nitride (AlN) substrate. Distributed polarization doping (DPD) was employed for both p-type and n-type layers of the p-n junction, instead of conventional impurity doping, to overcome the major bottleneck of AlN-based material: the control of conductivity. Capacitance–voltage measurements revealed that the net charge concentration agreed well with the DPD charge concentration expected from the device layer structure. The fabricated devices exhibited a low turn-on voltage of 6.5 V, a low differential specific ON-resistance of 3 M<inline-formula> <tex-math notation="LaTeX">$\Omega$</tex-math> </inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula>, electroluminescence (maximum at 5.1 eV), and an ideality factor of 2 for a wide range of temperatures (room temperature—573 K). Moreover, the breakdown electric field was 7.3 MV cm<inline-formula> <tex-math notation="LaTeX">$^{-\text{1}}$</tex-math> </inline-formula>, which was almost twice as high as the reported critical electric field of GaN at the same doping concentration. These results clearly demonstrate the usefulness of DPD in the fabrication of high-performance AlN-based power devices.

DOI： 10.1109/TED.2024.3367314

Temperature Dependence of α-Particle Detection Performance of GaN PIN Diode Detector

Nakagawa, H; Hayashi, K; Miyazawa, A; Honda, Y; Amano, H; Aoki, T; Nakano, T

SENSORS AND MATERIALS Vol. 36 ( 1 ) page： 169 - 176 2024

Language：English Publishing type：Research paper (scientific journal) Publisher：Sensors and Materials

Group-III nitride semiconductors, such as gallium nitride (GaN), have been proposed as novel materials for radiation detection owing to their wide bandgap and their ability to operate at high temperatures. In this study, the radiation detection properties of GaN PIN diode detectors were evaluated at high temperatures (~573 K). The energy spectrum peak profiles of241Am α-particles were obtained at different temperatures, confirming the operation of GaN PIN diodes up to 573 K. The peak positions shifted toward the lower-energy side and the full width at half maximum (FWHM) of the detection energy peak improved with increasing temperature. Furthermore, the variation in electron carrier mobility–lifetime product (μeτe) between 293 and 573 K was not significant. These results indicate the potential high-temperature operation of group-III nitride semiconductors. Additionally, the variation in each detection characteristic was caused by increasing the atmospheric temperature, which affected the mobility, lattice scattering, bandgap, and built-in potential differently.

DOI： 10.18494/SAM4647

15 GHz GaN Hi-Lo IMPATT Diodes With Pulsed Peak Power of 25.5 W

Kawasaki, S; Kumabe, T; Deki, M; Watanabe, H; Tanaka, A; Honda, Y; Arai, M; Amano, H

IEEE TRANSACTIONS ON ELECTRON DEVICES Vol. 71 ( 3 ) page： 1408 - 1415 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Electron Devices

The p+-n-n - n+ structure, known as Hi-Lo structure, was investigated in gallium nitride (GaN) single-drift-region (SDR) impact ionization avalanche transit-time (IMPATT) diodes to improve the output power and efficiency. The 15 GHz GaN Hi-Lo IMPATT diode was designed according to the Scharfetter and Gummel model under realistic conditions, suppressing the tunneling current (<10-4 cm2) and breakdown voltage (< 400 V). Even in such conditions, the calculated efficiency was higher than that of the p+-n abrupt junction structure and the improvement of RF characteristics was expected. The fabricated GaN Hi-Lo IMPATT diodes showed a clear avalanche breakdown and a pulsed microwave oscillation in the frequency range from 15 to 17 GHz. The maximum peak output power of 25.5 W and the efficiency of 2% were achieved, showing the highest values on microwave band GaN IMPATT diodes, and we confirmed that the Hi-Lo structure is effective for the high-power and high-efficiency operation of GaN IMPATT diodes.

DOI： 10.1109/TED.2023.3345822

Anisotropic hole transport along [0001] and [1120] direction in p-doped (1010) GaN

Lin, YY; Wang, J; Pristovsek, M; Honda, Y; Amano, H

JOURNAL OF APPLIED PHYSICS Vol. 134 ( 23 ) 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Physics

The anisotropic hole transport along [0001] and [1120] in the p-doped (1010) GaN layer was compared for layers grown on bulk (1010) GaN substrates and on (1010) sapphire. The sheet resistance along [0001] was 1.1 times larger on GaN substrates and even 1.2 times larger on sapphire than that along [1120]. The anisotropic hole transport on bulk GaN substrates is due to the anisotropy of the hole’s effective mass and the different contribution of carriers in different bands, whereas the larger anisotropy for GaN on sapphire is also due to additional scattering at stacking faults. The annealing process of metal Mg applied to the m-plane p-type GaN successfully results in a robust p-type ohmic contact, functioning as a p++ layer.

DOI： 10.1063/5.0177681

Improving the Barrier Height of N-Polar GaN Schottky Diodes Using Mg-Diffusion Process

Sarkar, B; Wang, J; Watanabe, H; Amano, H

IEEE TRANSACTIONS ON ELECTRON DEVICES Vol. 71 ( 3 ) page： 1416 - 1420 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Electron Devices

In this work, we report a low-cost methodology to increase the barrier height of N-polar GaN Schottky diodes. Physical vapor deposition (PVD) of Mg followed by a thermal diffusion anneal at 800 °C leads to the formation of N-polar GaN Camel diode offering a larger barrier height than the conventional N-polar GaN Schottky diodes. The increase in barrier height after the Mg diffusion process is validated using current-voltage ({I} - {V}) and capacitance-voltage (CV) measurements. A barrier height of 0.7 eV and a near-unity ideality factor observed in the N-polar GaN Camel diode confirms that the proposed Mg diffusion process is an alternative method for improving the performance of future N-polar GaN diodes.

DOI： 10.1109/TED.2023.3341831

Electron lifetime and diffusion coefficient in dopant-free p-type distributed polarization doped AlGaN

Kumabe, T; Kawasaki, S; Watanabe, H; Honda, Y; Amano, H

APPLIED PHYSICS LETTERS Vol. 123 ( 25 ) 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

Minority carrier properties in dopant-free p-type distributed polarization doped (DPD) AlGaN layers were investigated on the basis of the forward-biased current density-voltage (J-V) characteristics of p-n+ diodes. The fabricated p-DPD AlGaN/n+-AlGaN:Si diodes exhibited ideal electrical characteristics despite the absence of acceptor atoms in the p-type layer. The extracted Shockley-Read-Hall lifetime exceeded 300 ps, which was longer than that reported for p-GaN:Mg on GaN substrates with a similar acceptor concentration (20-50 ps). Moreover, the electron diffusion coefficient was about 20 cm2 s−1 at any temperature, which was convincing in terms of the electron mobility in DPD layers. The results suggest that p-DPD AlGaN has more desirable minority carrier properties than conventional p-GaN:Mg, particularly for bipolar device applications.

DOI： 10.1063/5.0180062

Ga-polar GaN Camel diode enabled by a low-cost Mg-diffusion process

Sarkar, B; Wang, J; Badami, O; Pramanik, T; Kwon, W; Watanabe, H; Amano, H

APPLIED PHYSICS EXPRESS Vol. 16 ( 12 ) 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Express

In this letter, we show that low-cost physical vapor deposition of Mg followed by a thermal diffusion annealing process increases the effective barrier height at the metal/Ga-polar GaN Schottky interface. Thus, for the first time, GaN Camel diodes with improved barrier height and turn-on voltage were realized compared to regular GaN Schottky barrier diodes. Temperature-dependent current-voltage characteristics indicated a near-homogeneous and near-ideal behavior of the GaN Camel diode. The analysis performed in this work is thought to be promising for improving the performance of future GaN-based unipolar diodes.

DOI： 10.35848/1882-0786/ad0db9

Using low-temperature growth to resolve the composition pulling effect of UV-C LEDs

Yoshikawa, A; Zhang, ZY; Kushimoto, M; Aoto, K; Sasaoka, C; Amano, H

APPLIED PHYSICS LETTERS Vol. 123 ( 22 ) 2023.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

One approach to improving the output power of ultraviolet (UV-C) light-emitting diodes (LEDs) is to adopt an electron-blocking layer (EBL) with a high barrier. However, the intended effect may not be realized because of the composition pulling effect, which is the unintended occurrence of a gradient layer at an AlGaN/AlGaN hetero-interface with substantial differences in the Al composition. Here, we demonstrate that low-temperature growth (i.e., <1000 °C) can be used to control the unintentional gradient layer at an AlN/AlGaN hetero-interface between a barrier layer and AlN-EBL with a difference in Al compositions of more than 30%. LEDs with an emission wavelength of 265 nm were fabricated, and an AlN-EBL was grown at low temperature to realize an abrupt interface. At an applied current of 100 mA, growing the EBL under low-temperature conditions improved the forward voltage by 0.5 V and remarkably improved the peak luminous intensity by 1.4-1.6 times. Our results can be used to realize UV-C LEDs with a steep EBL and further improve their device characteristics.

DOI： 10.1063/5.0183320

Multiplexing of bias-controlled modulation modes on a monolithic III-nitride optoelectronic chip

Zhang, H; Ye, ZQ; Yan, JB; Shi, F; Shi, ZM; Li, DB; Liu, YH; Amano, H; Wang, YJ

OPTICS LETTERS Vol. 48 ( 19 ) page： 5069 - 5072 2023.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Optics Letters

III-nitride optoelectronic chips have tremendous potential for developing integrated computing and communication systems with low power consumption. The monolithic, top–down approaches are advantageous for simplifying the fabrication process and reducing the corresponding manufacturing cost. Herein, an ultraviolet optical interconnection system is investigated to discover the way of multiplexing between emission and absorption modulations on a monolithic optoelectronic chip. All on-chip components, the transmitter, monitor, waveguide, modulator, and receiver, share the same quantum well structure. As an example, two bias-controlled modulation modes are used to modulate video and audio signals in the experiment presented in this Letter. The results show that our on-chip optoelectronic system works efficiently in the near ultraviolet band, revealing the potential breadth of GaN optoelectronic integration.

DOI： 10.1364/OL.503429

Dislocation Suppresses Sidewall-Surface Recombination of Micro-LEDs

Park, JH; Pristovsek, M; Cai, WT; Cheong, HJ; Kang, CM; Lee, DS; Seong, TY; Amano, H

LASER & PHOTONICS REVIEWS Vol. 17 ( 10 ) 2023.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Laser and Photonics Reviews

Nonradiative recombination rate that consists of dislocation-related nonradiative recombination rate (A0) and surface recombination rate (As) is one of the major parameters determining the performance of microlight-emitting diodes (µLEDs). Recent demonstrations improving the efficiency of blue InGaN or red AlGaInP µLEDs using specific methods such as atomic layer deposition or chemical treatment confirm the suppression of As. However, it is hardly found that those methods effectively improve the efficiency of red InGaN µLEDs so far. Here, it is discovered that the dislocation leads to an ineffective As. First, an intrinsic As degrades the external quantum efficiency (EQE) of blue InGaN µLEDs, resulting in EQE decreases with shrinking size. Second, panchromatic cathodoluminescence finds evidence that most of the carriers can be trapped before reaching the sidewall due to high A0. This results in shortened diffusion length of carriers and reduces the number of carriers reaching the sidewall. Consequently, the opposite trend of increasing EQE with shrinking size occurs in the case of red InGaN µLEDs due to an ineffective As. Furthermore, an 8.3 nm quantum well of InGaN with 13% Indium content that can reach a ≈690 nm wavelength at the low current is shown.

DOI： 10.1002/lpor.202300199

UV/DUV light emitters

Khan, A; Kneissl, M; Amano, H

APPLIED PHYSICS LETTERS Vol. 123 ( 12 ) 2023.9

Impact of graphene state on the orientation of III-nitride

Park, JH; Hu, N; Park, MD; Wang, J; Yang, X; Lee, DS; Amano, H; Pristovsek, M

APPLIED PHYSICS LETTERS Vol. 123 ( 12 ) 2023.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

We attempted to grow (10-13) semi-polar GaN on graphene to confirm the possibility of a remote epitaxy of semi-polar GaN. Single crystalline (10-13) GaN was obtained on an optimized template using optimized growth conditions. However, (10-13), (0002), and other GaN orientations were found under the same growth conditions on a graphene-coated template. Scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy revealed that multi-domain GaN and (0002) GaN occurred in areas with a damaged graphene interfacial layer and intact graphene, respectively. Raman spectroscopy confirmed that graphene could survive under the growth conditions used here. Using cross-sectional scanning electron microscopy, we propose a simple approach to distinguish damaged graphene. Although the remote epitaxy of semi-polar GaN has not been demonstrated despite the usage of an optimized template and growth conditions, our results confirm the importance of the interfacial state in determining the crystallinity of the overgrown layer.

DOI： 10.1063/5.0157588

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