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The use of μLEDs in self‐luminous displays is crucial for the development of high‐efficiency displays for virtual space services. For this purpose, a stacked monolithic GaInN‐based micro light‐eimtting diodes (μLED) device that emits red, green, and blue (RGB) light is obtained. The RGB layers are connected via tunnel junction (TJ) layers. The pixel density is 330 ppi (35 × 15 μm2 of μLED mesa area corresponding to the emission). The cross‐sectional transmission electron microscopy analysis indicates that there is not a significant increase in threading dislocations even after stacking the three RGB active layers and two TJ layers. In addition, the X‐ray diffraction reciprocal lattice space mapping shows that all the layers grow almost coherently with respect to the GaN substrate. A detailed evaluation of the resulting device shows that the BT.2020 color gamut coverage reaches a maximum of 71%, and the luminance is sufficiently high for head‐mounted display applications. Redshifting of the emission wavelength of the red μLEDs by increasing the InN mole fraction in the GaInN active layer would likely lead to improvement of the color gamut coverage in future studies. [ABSTRACT FROM AUTHOR]

The pump and probe technique in Raman spectroscopy of the E2 (high) mode is exploited to uncover the enhancing factor of the phonon transport across Ga1−xInxN/GaN interfaces. Two samples are investigated: one with a uniform x of 0.09 and another one with a graded variation in x from 0.17 to 0 along the depth direction. Lateral phonon transport is obtained by scanning the 532-nm probing laser from the irradiation position of the 325-nm heating laser. No difference in the lateral diffusion length is observed between the two samples, while the transport probability across the interface is higher for the sample with the graded variation in x than the sample with the uniform x of 0.09. The microscopic images of the decrease in the mode energy or the increase in temperature of the GaN layer reveal that the local phonon transport across the heterointerface is enhanced in regions with low differences in the phonon mode energy between the GaN and GaInN rather than the difference in crystal quality. [ABSTRACT FROM AUTHOR]

We present results from a study addressing the unbiased water-splitting process and its side reactions on GaN-based photoelectrodes decorated with NiOx, FeOx, and CoOx nanoparticles. Observations involving physicochemical analyses of liquid and vapour phases after the experiments were performed in 1 M NaOH under ambient conditions. A water-splitting process with GaN-based photoelectrodes results in the generation of hydrogen gas and hydrogen peroxide. Quantification of the water-splitting chemical mechanism gave numerical values indicating an increase in the device performance and restriction of the GaN electrocorrosion with surface modifications of GaN structures. The hydrogen generation efficiencies are ηH2(bare GaN) = 1.23%, ηH2(NiOx/GaN) = 4.31%, ηH2(FeOx/GaN) = 2.69%, and ηH2(CoOx/GaN) = 2.31%. The photoelectrode etching reaction moieties Qetch/Q are 11.5%. 0.21%, 0.26% and 0.20% for bare GaN, NiOx/GaN, FeOx/GaN, and CoOx/GaN, respectively. [ABSTRACT FROM AUTHOR]

Nitrides are of particular interest in energy applications given their suitability to photocatalytically generate H2 from aqueous solutions. However, one of the drawbacks of nitrides is the decomposition they suffer when used in photoelectrochemical cells. Here, we report the improvement of the catalytic performance and chemical stability of a GaN electrode when it is decorated with Fe2O3 particles compared with an undecorated electrode. Our results show a higher reaction rate in the Fe2O3/GaN electrode, and that photocorrosion marks take more than 20 times longer to appear on it. We also characterized the crystalline properties of the Fe2O3 particles with transmission electron microscopy. The results show that the Fe2O3 particles keep an epitaxial relationship with GaN that follows the Fe2O3 { 0003 } | | GaN { 0001 } and Fe2O3 [ 11 2 ¯ 0 ] | | GaN [ 1 1 ¯ 00 ] symmetry constraints. We also characterized an Fe2O3 (thin film)/GaN electrode, however it did not present any catalytic improvement compared with a bare GaN electrode. The epitaxial relationship found between the Fe2O3 thin film and GaN exhibited the Fe2O3 { 11 2 ¯ 0 } | | GaN { 0002 } and Fe2O3 [ 3 3 ¯ 00 ] | | GaN [ 11 2 ¯ 0 ] symmetry constraints. [ABSTRACT FROM AUTHOR]

Abstract: We observed the growth of the Ga0.80In0.20N (2nm)/GaN (3nm) superlattice (SL) structure by in situ X-ray diffraction (XRD) monitoring. The satellite peaks from the −1st to the +1st order can be obtained from these in situ XRD spectrums. From the full width at half maximums (FWHMs) of the 0th and −1st satellite peaks as a function of the SL periods, we observed a clear trend in each FWHM. It was found that by analyzing this trend along with florescence microscopic and transmission electron microscopic analysis, an analysis of the In segregation and misfit dislocation are possible. Accordingly, if we employ in situ XRD under various growth conditions, the optimization of the growth conditions will become easier because it would be possible to determine the number of periods at which In segregation and misfit dislocation increases by only one growth procedure. [Copyright &y& Elsevier]

Abstract: The electrical and optical properties of Mg-doped a- and c-plane GaN films grown by metalorganic vapor phase epitaxy were systematically investigated. The photoluminescence spectra of Mg-doped a- and c-plane GaN films exhibit strong emissions related to deep donors when Mg doping concentrations are above 1×1020 cm−3 and 5×1019 cm−3, respectively. The electrical properties also indicate the existence of compensating donors because the hole concentration decreases at such high Mg doping concentrations. In addition, we estimated the N D /N A compensation ratio of a- and c-plane GaN by variable-temperature Hall effect measurement. The obtained results indicate that the compensation effect of the Mg-doped a-plane GaN films is lower than that of the Mg-doped c-plane GaN films. [ABSTRACT FROM AUTHOR]

The document is an erratum for an article titled "Photoluminescence Emission Efficiency Analysis Methodology by Integrating Raman Spectroscopy of the A1(LO) and E2(high) Phonons in a GaInN/GaN Heterostructure." It corrects Equation 4a and presents revised figures related to carrier recombination processes and temperature increases in the GaInN/GaN heterostructure. The authors recommend a specific parameter set for GaN based on statistical considerations and discuss the correlation between temperature increase and photoluminescence emission efficiency in different regions of the heterostructure. Further analysis using the Boltzmann equation is suggested for a comprehensive understanding of carrier transport dynamics. [Extracted from the article]

Abstract: We succeeded in growing high-crystalline-quality thick (101¯1¯) Ga0.92In0.08N films on a grooved (101¯1¯) GaN/(101¯2¯) 4H-SiC underlying layer. We also fabricated GaInN/GaN multiple quantum wells (MQWs) with a peak wavelength of 580nm on a high-crystalline-quality thick GaInN film. The photoluminescence intensity of the MQWs is about six times higher than that of MQWs grown on planar GaN and twice as high as that of MQWs grown on a GaN underlying layer having the same grooved structure. [Copyright &y& Elsevier]

The pump and probe technique in Raman spectroscopy is used to demonstrate the phonon transport properties of an In 0.05 Ga 0.95 N/GaN heterostructure. The pump laser generates phonons via the energy relaxation of the generated carriers in the electronic energy bands of the InGaN layer, and the Raman signal is obtained using the probe laser. In the present study, 532-nm and 325-nm lasers are utilized. The phonon transport from the InGaN layer to the GaN layer across the heterointerface is blocked near the crystal defects inherited from the GaN layer. This phenomenon is consistent with our previous report demonstrating the blocking of phonon transport across the In 0.16 Ga 0.84 N/GaN heterointerface near the misfit dislocations in the In 0.16 Ga 0.84 N layer. Lateral phonon transport over a distance of 20 μm is observed, which is dominated by diffusive phonon transport. This method has the advantage of enabling the study of phonon transport processes inside and at interfaces of films with crystal defects by visualizing the shift of phonon-mode energies due to local heating. [ABSTRACT FROM AUTHOR]