Influence of the N 2 /H 2 ratio on the structural features of In x Ga 1 − x N/GaN films grown by MOCVD (original) (raw)
Related papers
Microstructures of GaN and InxGa1-xN Films Grown by MOCVD on freestanding GaN Templates
MRS Proceedings, 2002
We summarize structural properties of thick HVPE GaN templates from the point of view of their application as substrates for growth of nitride layers. This is followed by the results of optical and structural studies, mostly transmission electron microscopy, of nitride layers grown by MOCVD on top of the HVPE substrates. The results indicate high structural quality of these layers with a low density of threading dislocations (in the range of 106 cm-2). Convergent beam electron diffraction studies showed that the MOCVD GaN films have Ga-polarity, the same polarity as the HVPE GaN substrates. Structural studies of an InGaN layer grown on top of the MOCVD GaN film showed the presence of two layers, which differed in lattice parameter and composition. The upper layer, on the top of the structure had a clattice parameter about 2 % larger than that of GaN and contained 10.3 ± 0.8 % of In. Values measured for the thinner, intermediate layer adjacent to the GaN layer were about 2.5 times lo...
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2012
CuAlO x thin films were prepared at three substrate temperatures ͑T S = 60, 300, and 600°C͒ and two oxygen partial pressures ͑P O 2 = 0.5 and 2 mTorr͒ via dc reactive magnetron sputtering from Cu-Al 50-50 at. % alloy targets and subsequent annealing. As-deposited films with P O 2 = 0.5 mTorr were oxygen deficient; although the delafossite structure formed upon annealing, electrical properties were poor. Films deposited with P O 2 = 2 mTorr transformed into the delafossite structure and exhibited p-type conductivity after annealing under N 2 at temperatures T A Ն 750°C. Conductivity generally increased with increasing T S and decreasing T A. A special case of P O 2 = 2 mTorr and low T S ͑60°C͒ resulted in a partially crystalline oxide phase that transformed into the delafossite structure at T A = 700°C and yielded the highest conductivity of 1.8 S cm −1. In general, a T A near the phase formation boundary led to an increase in conductivity. Low-temperature hydrothermal annealing was also investigated and shown to produce mixed phase films exhibiting the delafossite structure along with CuO, AlOOH, and Al 2 O 3 .
Journal of Crystal Growth, 2007
We systematically investigate the compositional inhomogeneity near surface, interface, and dislocation in In x Ga 1Àx N thin films on GaN(0 0 0 1) by using our empirical interatomic potential and the Monte Carlo (MC) method. The compositional inhomogeneity is discussed by evaluating individual contribution such as strain relief at the surface and the interface between In x Ga 1Àx N and GaN with/ without misfit dislocations. The empirical potential calculations reveal that the dislocation core energy for bulk InN (1.51 eV) is smaller than that of GaN (1.81 eV). This suggests that In atoms preferentially reside in the lattice sites near the dislocation core in In x Ga 1Àx N. The MC simulation clarifies that In surface segregation is found in In x Ga 1Àx N thin films pseudomorphically grown on GaN(0 0 0 1), where the surface composition of In is greater than that of bulk In composition because of strain relief and bond energy profit of In atoms at the surface. Further MC simulation for the system including both surface and misfit dislocations implies that the In atoms segregate at the surface strongly while In atoms segregate near the misfit dislocations weakly. r
Japanese Journal of Applied Physics, 2013
The growth of InGaN with intermediate In compositions on GaN/sapphire template and AlN/Si(111) substrate has been comparatively studied. By using an metalorganic vapor phase epitaxy (MOVPE) system with a horizontal reactor, InGaN films are grown at a temperature of 600-800 C in the pressure of 150 Torr. By optimizing growth temperature and trimethylindium=ðtrimethylindium þ triethylgalliumÞ molar ratio, single crystalline In x Ga 1Àx N with x ¼ 0{1 are successfully grown on both substrates. The films grown at a relatively high temperature (!700 C) with In compositions of 0.3 or less show phase separation when their thickness exceeds a critical value (0.25-0.4 m), while the samples grown at 600 C with In compositions of 0.35-0.5 show no phase separation even if the thickness is increased to 0.7 m. To evaluate the crystalline quality of grown films, FWHM of X-ray rocking curve (XRC) for InGaN(0002), tilt, is measured. There is no marked difference in tilt data between films grown on GaN/-Al 2 O 3 (0001) and AlN/Si(111). For the samples grown at 600 C with In contents of 0.35-0.5, tilt data are drastically increased and widely scattered suggesting the existence of important unknown parameters that govern crystalline quality of InGaN grown at a relatively low temperature.
Japanese Journal of Applied Physics, 2012
The accurate alloy composition of a nonpolar InGaN grown on m-plane GaN is estimated from X-ray reciprocal-space maps (RSMs) of (20 21) and (21 30) diffractions. In this estimation, the anisotropic residual strain in m-plane is carefully considered. In order to avoide the error which may be generated by the anisotropic strain and tilted domains in the film of InGaN, the lattice constants along m-, a-, and c-directions are determined using a pair of two RSMs normalized to the unit reciprocal vector along m-direction. The indium content of InGaN is derived from RSMs data using Poisson effect and Vegard's law. Based on this method, the incorporation of indium into InGaN is investigated. This incorporation is found to be promoted with the increase in the substrate miscut angle and the growth rate. From the precise analysis of RSMs, some of the InGaN domains on m-plane GaN substrates are found to be tilted toward AEa-direction despite of the substrate miscut toward c-direction.
V-defects and dislocations in InGaN/GaN heterostructures
Thin Solid Films, 2005
In the growth of InGaN/GaN multi-quantum well (MQW) heterostructures by metal organic chemical vapor deposition, V-defects attached to threading dislocations have been observed and investigated. Energy-dispersive X-ray analysis and conventional transmission electron microscopy studies were carried out in order to determine the In composition and investigate the behavior of the dislocations. The Vdefects are limited by {1011} lattice planes, they are attached to threading dislocations and may start at the third quantum well. The associated dislocation runs up into the overgrown GaN layer. Some (a+c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-shape defect. D
Characteristics of the surface microstructures in thick InGaN layers on GaN
Optical Materials Express, 2013
This paper focuses on a comparative study of optical, morphological, microstructural and microcompositional properties of typical InGaN samples which exhibit V-defects but also two additional surface defects features, referred to as inclusion#1 (Ic1) and inclusion#2 (Ic2). HR-XRD, AFM, SEM, STEM and EDX are used to characterize such defects. Furthermore, hyperspectral mapping, spot mode and depth-resolved CL measurements provided useful informations on the optical emission properties and microstructure. The main characteristic of Ic1 luminescence peak is a decrease in intensity and no obvious shift in the CL peak position when going from the outside to the middle of such defect. More interesting was Ic2 which is shown to be local 3D top surface In-rich InGaN domains embedded in an homogeneous InGaN matrix. In fact, this study pointed out that close to the interface GaN/InGaN, it exists a 30 nm thick fully strained InGaN layer with constant indium incorporation. As the growth proceeds spatial fluctuation of the In content is observed and local In-rich 3D domains are shown to emerge systematically around threading dislocations terminations.
Investigation of structural, optical and morphological properties of InGaN/GaN structure
Applied Physics A, 2018
In this study, InGaN/GaN structure is investigated in the temperature range of 300-500 °C with steps of 50 °C. InGaN/ GaN multi-quantum well structure is deposited on c-orientated sapphire wafer by metal organic chemical vapour deposition method. All the parameters except for temperature kept constant during growth period. InGaN/GaN structures with different In content are investigated by XRD technique. Their structural, optical and morphological characteristics are determined by high resolution X-ray diffraction, Fourier transform spectroscopy (FTIR), photo luminescence (PL), transmission and atomic force microscopy (AFM). According to FTIR and PL spectra's, it is noticed that band gap values coincide with blue region in the electromagnetic spectrum. As a result of transmission measurements it is seen that light is completely absorbed by the sample at approximately 390 nm. Using XRD technique, dislocation densities and strain are calculated. Full width at half maximum of the XRD peak values gained from X-ray diffraction are used in an alternative method called Williamson-Hall (W-H). Using W-H method, lateral and vertical crystal lengths and tilt angles are determined. Surface roughness parameters are investigated by AFM. Different properties of GaN and InGaN layers are compared as dependent on increasing temperature. According to AFM images it is seen that these structures have high surface roughness and large crystal size. All the results yielded from the mentioned methods are in good agreement with the previous works done by different authors.