Sakuntam Sanorpim

Structural Investigation of Cubic-Phase InN on GaAs (001) Grown by MBE under In- and N-Rich Growth Conditions

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.

Microstructures of InN film on 4H-SiC （0001） substrate grown by RF-MBE

InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF-MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ~ 5.5 nm was grown on the substrate. Surface morphology, microstructure and structural quality of InN film were investigated. Micro-structural defects, such as stacking faults and anti-phase domain in InN film were carefully investigated using transmission electron microscopy (TEM). The results show that a high density of line contrasts, parallel to the growth direction (c-axis), was clearly observed in the grown InN film. Dark field TEM images recorded with diffraction vectors g = 11

High Cubic‐Phase Purity InN on MgO (001) Using Cubic‐Phase GaN as a Buffer Layer

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High Resolution X-Ray Diffraction and Raman Scattering Studies of Cubic-Phase InN Films Grown by MBE

0 and g = 0002 revealed that such line contrasts evolved from a coalescence of the adjacent misoriented islands during the initial stage of the InN nucleation on the substrate surface. This InN nucleation also led to a generation of anti-phase domains.

Effect of N Incorporation on Growth Behavior of InGaAsN/GaAs/Ge Multi-Layered Structure by MOVPE

High cubic‐phase purity InN films were grown on MgO (001) substrates by molecular beam epitaxy with a cubic‐phase GaN buffer layer. The cubic phase purity of the InN grown layers has been analyzed by high resolution X‐ray diffraction, μ‐Raman scattering and transmission electron microscopy. It is evidenced that the hexagonal‐phase content in the InN overlayer much depends on hexagonal‐phase content in the cubic‐phase GaN buffer layer and increases with increasing the hexagonal‐phase GaN content. From Raman scattering measurements, in addition, the InN layer with lowest hexagonal component (6%), only Raman characteristics of cubic TOInN and LOInN modes were observed, indicating a formation of a small amount of stacking faults, which does not affect on vibrational property.

Effect of Substrate-Surface Orientation on the N Incorporation in GaAsN Films on GaAs Grown by MOVPE

We demonstrate the use of high resolution X-ray diffraction and Raman scattering to assess the generation of hexagonal-phase in the cubic-phase InN (c-InN) films on MgO substrates grown by molecular beam epitaxy with a cubic-phase GaN buffer layer. The X-ray reciprocal-lattice space mapping was used to examine the hexagonal-phase generated on the cubic (111) planes in the c-InN films. Ratio of hexagonal to cubic components in the c-InN grown layers was estimated from the ratio of the integrated X-ray diffraction intensities of cubic (002) and hexagonal (10-11) reflections measured by ω–scans. Amount of hexagonal-phase presented in the c-InN films was determined in the range of 6 to 24%. It was found that the Raman characteristics are also sensitive to hexagonal-phase presented in the c-InN films. For the lowest amount of hexagonal-phase (6%), only Raman scattering characteristics of c-InN was observed, indicating formation of a small amount of stacking faults, which not affected on the vibrational property. Based on our results, relatively easy access to the generation of hexagonal-phase suggests that it may be very useful for HRXRD and Raman scattering measurements of c-InN.

InGaPN/GaP Lattice-Matched Single Quantum Wells on GaP (001) Grown by MOVPE

We have investigated an effect of N incorporation on InGaAsN on Ge (001), which is proposed to be a part of the InGaP(N)/InGaAs/InGaAsN/Ge four-junction solar cell, and on its growth behavior. Results obtained from high resolution X-ray diffraction and Raman scattering demonstrated that high quality In0.11Ga0.89As1-yNy films with N (y) contents up to 5% were successfully grown on n-type doped Ge (001) substrate by metalorganic vapor phase epitaxy using low-temperature (500°C) GaAs buffer layer. As expectation, the In0.11Ga0.89As0.96N0.04 film is examined to be under lattice-matching condition. Anti-phase domains were observed for the film without N incorporation, which exhibits submicron-size domains oriented along the [110] direction on the grown surface. With increasing N content, the domains become less orientation, and present in a larger domain size. Based on results of transmission electron microscopy, a high density of anti-phase domains was clearly observed at the interface of low-temperature GaAs buffer layer and Ge substrate. On the other hand, it is found to drastically reduce within the N-contained InGaAsN region. Furthermore, the lattice-matched In0.11Ga0.89As0.96N0.04 film is well developed to reduce the density of anti-phase domains.

MOVPE Growth Window for High-Nitrogen GaAsN Alloy Films for Long Wavelength Emission

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.

TEM Analysis of Planar Defects in InGaAsN and GaAs Grown on Ge (001) by MOVPE

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.

Micro-Raman Investigation of Epitaxial Lateral Overgrown Cubic GaN on Patterned GaAs (001) with Different Mask Stripe Directions

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.