Papers by Author: R. Katayama

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Authors: S. Sanorpim, F. Nakajima, R. Katayama, Kentaro Onabe
Abstract: The high quality GaAsN epitaxial films with the typical thickness of 150-200 nm and the N contents up to 5.5% were grown by MOVPE. The maximum N content of 2.75% at the growth temperature of 550 oC was enhanced to 5.1% at 500 oC and 5.5% at 450 oC. The lower growth temperature may efficiently suppress desorption of N atoms from the growing surface. The narrow high-resolution X-ray diffraction peaks and the clear Pendellösung fringes indicate that the GaAsN films with high uniformity and fairly flat interface were obtained. The 6K-photoluminescence (PL) peak energy of the GaAsN films was varied from 1.38 eV to 1.01 eV with increasing N content up to 2.75%, but no near-band-edge emission was observed in the higher-N-content films, indicating the increase of nonradiative recombination centers caused by the N-related lattice imperfections. Besides, after post growth thermal annealing at 650 oC for 2 min, PL spectrum shows that the near-band-edge emission as low as 0.97 eV (1.3 μm) have been achieved with the film of 5.1% N.
Authors: S. Sanorpim, P. Kongjaeng, R. Katayama, Kentaro Onabe
Abstract: The use of an InGaAs buffer layer was applied to the growth of thick InxGa1-xAs1-yNy layers with higher In contents (x > 30%). In order to obtain the lattice-matched InGaAsN layer having the bandgap of 1.0 eV, the In0.2Ga0.8As was chosen. In this work, the In0.3Ga0.7As0.98N0.02 layers were successfully grown on closely lattice-matched In0.2Ga0.8As buffer layers (InGaAsN/InGaAs). Structural quality of such layers is discussed in comparison with those of the In0.3Ga0.7As0.98N0.02 layers grown directly on the GaAs substrate (InGaAsN/GaAs). Based on the results of transmission electron microscopy, the misfit dislocations (MDs), which are located near the InGaAsN/GaAs heteroepitaxial interface, are visible by their strain contrast. On the other hand, no generation of the MDs is evidenced in the InGaAsN layer grown on the In0.2Ga0.8As pseudosubstrate. Our results demonstrate that a reduction of misfit strain though the use of the pseudosubstrate made possible the growth of high In-content InGaAsN layers with higher crystal quality to extend the wavelength of InGaAsN material.
Authors: P. Klangtakai, S. Sanorpim, S. Kuboya, R. Katayama, Kentaro Onabe
Abstract: The GaAs1-xNx alloy semiconductor has been grown on GaAs (001), (111)A and (011) substrates by metalorganic vapor-phase epitaxy. High resolution X-ray diffraction and Raman scattering were employed to examine the effective N content and the growth rate, as a function of the substrate-surface orientation. The growth rate, which was assessed though the clear Pendellösung fringes, and the N content were found to change dramatically with the substrate-surface orientations. The N content was determined in the order (111)A > (001) > (011). While, the growth rate is in the order, (001) > (011) > (111)A. The effect of substrate-surface orientation on the N incorporation found in the present study is interpreted in terms of the difference in the growth rate on each surface orientation and the number of dangling bonds with which the N atoms can be trapped on the growing surface. Our results show that controlled nitrogen incorporating for GaAsN is successfully achieved and can be applied to the fabrication of some novel structures such as a spontaneous N content modulated structure, which is applicable to high performance long wavelength laser diodes.
Authors: D. Kaewket, S. Sanorpim, Sukkaneste Tungasmita, R. Katayama, Kentaro Onabe
Abstract: Highly luminescence lattice-matched InxGa1-xP1-yNy/GaP single quantum wells (SQWs) on GaP (001) substrates were successfully grown by metalorganic vapor phase epitaxy (MOVPE). High-resolution X-ray diffraction measurements established that the lattice-matched InxGa1-xP1-yNy/GaP SQWs with various In (x = 0.050, 0.080, 0.135) and N (y = 0.025, 0.048, 0.071) contents were realized with excellent crystal quality and fairly flat interfaces. The results of photoluminescence (PL) and PL-excitation (PLE) showed the strong visible light emission (yellow to red emission) from the SQWs. With increasing In and N contents, the PL peak position and the PLE absorption edge exhibited the red-shift to lower energy, indicating the lowering of the InGaPN conduction band edge. The conduction band offset (∆Ec) of the InGaAPN/GaP quantum structure was estimated to be as high as 270 to 480 meV, which depends on the In and N contents in the well. Our results demonstrate that this novel InGaPN/GaP SQW system appropriates for the fabrication of light-emitting and laser diodes.
Authors: S. Sanorpim, D. Kaewket, Sukkaneste Tungasmita, R. Katayama, Kentaro Onabe
Abstract: Optical transitions in the In0.050Ga0.950P0.975N0.025/GaP lattice-matched single quantum wells (SQWs) with different well widths (LZ = 1.6 - 6.4 nm) have been investigated by low-temperature photoluminescence (PL) and PL-excitation (PLE). PL spectra showed the strong visible emission from the samples which attracted to a variety of optoelectronic device applications such as light emitting and laser diodes. Comparing to the bulk film, the PL peak position and the fundamental absorption edge of PLE spectra exhibit blue-shift, which is corresponded to the quantum confinement effect by the well. Comparison between the absorption edge of PLE spectra and the finite square well calculation demonstrate that the effective bandgap energy of the InGaPN/GaP system is might be originated mainly from the N-related localized states.
Authors: S. Kuntharin, S. Sanorpim, T. Nakamura, R. Katayama, Kentaro Onabe
Abstract: We have investigated effect of the In- and N-rich growth conditions on the structural modification of cubic-phase InN (c-InN) films grown on GaAs (001) substrates by rf-plasmaassisted molecular beam epitaxy (RF-MBE). High resolution x-ray diffraction (HRXRD) and Raman scattering measurements were performed to examine the hexagonal phase generation in the c-InN grown films. It is evident that higher crystal quality c-InN films with higher cubic phase purity (~82%) were achieved under the In-rich growth condition. On the other hand, for the N-rich growth condition, the c-InN films exhibited higher incorporation of hexagonal phase, which is generated in the cubic phase through the incidental stacking faults on the c-InN (111) planes. Our results demonstrate that the In-rich growth condition plays a critical role in the growth of high quality c-InN films with higher cubic phase purity.
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