Browsing by Author "Chen, H. G."

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Characteristics of a-plane GaN with the SiN(x) insertion layer grown by metal-organic chemical vapor deposition
(2008-11-15)
Ko, T. S.
;
Wang, T. C.
;
Huang, H. M.
;
Chen, J. R.
;
Chen, H. G.
We utilized in-situ-grown SiN(x) insertion layers to mitigate part of dislocations stretching in nonpolar a-plane GaN films using metal-organic chemical vapor deposition. Both X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements revealed that better crystal quality and smoother surface could be obtained when the in-situ SiN(x) layer was inserted closer to the r-plane sapphire substrate and indicated that the in-situ SiN(x) insertion layer could suppress dislocations caused by lattice mismatch between the sapphire and epitaxial layers. In addition, photoluminescence and cathodoluminescence measurements confirmed the effect of the in-situ SiN(x) insertion layer on the optical properties of the improved a-plane GaN thin film, which is consistent with the XRD and AFM analyses and suggested reduction in the density of nonradiative centers. (C) 2008 Elsevier B.V. All rights reserved.
Characteristics of a-plane GaN with the SiNx insertion layer grown by metal-organic chemical vapor deposition
(2008-11-15)
Ko, T. S.
;
Wang, T. C.
;
Huang, H. M.
;
Chen, J. R.
;
Chen, H. G.
We utilized in-situ-grown SiNx insertion layers to mitigate part of dislocations stretching in nonpolar a-plane GaN films using metal-organic chemical vapor deposition. Both X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements revealed that better crystal quality and smoother surface could be obtained when the in-situ SiNx layer was inserted closer to the r-plane sapphire substrate and indicated that the in-situ SiNx insertion layer could suppress dislocations caused by lattice mismatch between the sapphire and epitaxial layers. In addition, photoluminescence and cathodoluminescence measurements confirmed the effect of the in-situ SiNx insertion layer on the optical properties of the improved a-plane GaN thin film, which is consistent with the XRD and AFM analyses and suggested reduction in the density of nonradiative centers. (C) 2008 Elsevier B.V. All rights reserved.
InGaN/GaN nanostripe grown on pattern sapphire by metal organic chemical vapor deposition
(2007-01-01)
Ko, T. S.
;
Wang, T. C.
;
Gao, R. C.
;
Lee, Y. J.
;
Lu, T. C.
The authors have used metal organic chemical vapor deposition to grow InGaN/GaN multiple quantum well (MQW) nanostripes on trapezoidally patterned c-plane sapphire substrates. Transmission electron microscopy (TEM) images clearly revealed that the MQWs grew not only on the top faces of the trapezoids but also on both lateral side facets along the [0001] direction defined by the selected area electron diffraction pattern. Meanwhile, dislocations that stretched from the interfaces between the GaN and the substrates did not pass through the MQWs in the TEM observation. Microphotoluminescence measurements verified that the luminescence efficiency from a single nanostripe was enhanced by up to fivefold relative to those of regular thin film MQW structures. Observation of the cathodoluminescence identified the areas of light emission and confirmed that enhanced emission occurred from the nanostripes. (c) 2007 American Institute of Physics.
Observation of strong red photoluminescence with broadband in indium oxynitride nanoparticles
(2006-07-01)
Ko, T. S.
;
Chu, C. P.
;
Chen, H. G.
;
Lu, T. C.
;
Kuo, H. C.
Indium oxynitride nanoparticles were synthesized on a silicon substrate in nitrogen atmosphere using the method involving thermal evaporation of pure indium in a two-zone reactor. Nanoscale compositional analysis by energy dispersion, spectrum showed the existence of indium oxynitride compound. X-ray diffraction analysis further confirmed high crystallization and nitrogen atom existence within the nanoparticles. Scanning electron microscopy investigations showed shape transformation from amorphous sphere to well-shaped octahedron with an average nanoparticle size ranging from 50 nm to 1 mu m when the growth temperature of the substrate was increased from 600 to 900 degrees C. Photoluminescence study was performed on the indium oxynitride nanoparticle samples grown at different temperatures. It was found that with increasing growth temperatures there was not only the formation of high quality indium oxynitride nanoparticles but also an increase in the intensities of emissions. These nanoparticles grown at 900 degrees C could emit a strong photoluminescence spectrum centered around 700 nm with a broad full width at half maximum of about 250 nm, spanning the whole red segment. (c) 2006 American Vacuum Society.
Observations on surface morphologies and dislocations of a-plane GaN grown by metal organic chemical vapor deposition
(2007)
Ko, T. S.
;
Wang, T. C.
;
Chen, H. G.
;
Gao, R. C.
;
Huang, G. S.
In this study, we grew non-polar a-plane GaN thin films on r-plane sapphire using a series of growth conditions by metal-organic chemical vapor deposition. The results showed that high temperature and low-pressure conditions benefited two-dimension growth could lead to a fully coalesced a-plane GaN layer with a very smooth surface. The best surface morphology with an excellent mean roughness of 10.5 angstrom was obtained. The different thickness AlN as a nucleation layer and the different delta/beta ratio were also considered. The results revealed that the surface morphology would get worse when the thickness of nucleation layer and delta/beta ratio were away from the values of optimal condition. The observation of transmission electronic microscopy shown the lowest density of threading dislocations was 1.85x10(10) /cm(2). (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Study on optimal growth conditions of a-plane GaN grown on r-plane sapphire by metal-organic chemical vapor deposition
(2007-03-15)
Ko, T. S.
;
Wang, T. C.
;
Gao, R. C.
;
Chen, H. G.
;
Huang, G. S.
Non-polar a-plane (1 1 (2) over bar 0) GaN thin films were grown on r-plane (1 (1) over bar 0 2) sapphire substrates by metal-organic chemical vapor deposition. In order to obtain a-plane GaN films with better crystal quality and surface morphology, detailed comparisons between different growth conditions were investigated. The results showed that high-temperature and low-pressure conditions facilitating two-dimensional growth could lead to a fully coalesced a-plane GaN layer with a very smooth surface. The best mean roughness of the surface morphology was 10.5 angstrom. Various thickness values of AlN nucleation layers and the V/III ratios for growth of the a-plane GaN bulk were also studied to determine the best condition for obtaining a smooth surface morphology of the a-plane GaN layer. (c) 2007 Elsevier B.V. All rights reserved.