Browsing by Author "Yang, Chung-Pei"

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Characterization and density control of GaN nanodots on Si (111) by droplet epitaxy using plasma-assisted molecular beam epitaxy
(2014-12-17)
Yu, Ing-Song
;
Chang, Chun-Pu
;
Yang, Chung-Pei
;
Lin, Chun-Ting
;
Ma, Yuan-Ron
In this report, self-organized GaN nanodots have been grown on Si (111) by droplet epitaxy method, and their density can be controlled from 1.1 x 10(10) to 1.1 x 10(11) cm(-2) by various growth parameters, such as substrate temperatures for Ga droplet formation, the pre-nitridation treatment of Si substrate, the nitridation duration for GaN crystallization, and in situ annealing after GaN formation. Based on the characterization of in situ RHEED, we can observe the surface condition of Si and the formation of GaN nanodots on Si. The surface nitridaiton treatment at 600 degrees C provides a-SiNx layer which makes higher density of GaN nanodots. Crystal GaN nanodots can be observed by the HRTEM. The surface composition of GaN nanodots can be analyzed by SPEM and mu-XPS with a synchrotron x-ray source. We can find GaN nanodots form by droplet epitaxy and then in situ annealing make higher-degree nitridation of GaN nanodots.
GaN Layers on Si (111) from Nanocolumns to Nanorods by Plasma-Assisted Molecular Beam Epitaxy
(2015-10)
Yu, Ing-Song
;
Liang, Wen-Han
;
Yang, Dian-Long
;
Yang, Chung-Pei
;
Chang, Chun-Pu
In this report, the characterization of GaN layers grown on p-type Si (111) substrate by plasma-assisted molecular beam epitaxy was investigated. For different growth temperatures (750 degrees C, 800 degrees C and 850 degrees C) and N/Ga flux ratios (0.26, 0.46 and 0.92), we can find the GaN layers transition from nanocolumns to nanorods structures. During the epitaxy of GaN, nanocolumns in the thin films with poor crystal quality were obtained for the growth parameters of low substrate temperature or Ga-rich condition. However, the growth at high substrate temperature or N-rich condition formed GaN nanorods structure, and was beneficial to the crystallization of GaN layers with preferential orientation (0001). In the end, the possible growth mechanism of GaN nanocolumns and nanorods was discussed in the letter.
GaN Layers on Si (111) from Nanocolumns to Nanorods by Plasma-Assisted Molecular Beam Epitaxy
(2015-10-01)
Yu, Ing-Song
;
Liang, Wen-Han
;
Yang, Dian-Long
;
Yang, Chung-Pei
;
Chang, Chun-Pu
In this report, the characterization of GaN layers grown on p-type Si (111) substrate by plasma-assisted molecular beam epitaxy was investigated. For different growth temperatures (750 degrees C, 800 degrees C and 850 degrees C) and N/Ga flux ratios (0.26, 0.46 and 0.92), we can find the GaN layers transition from nanocolumns to nanorods structures. During the epitaxy of GaN, nanocolumns in the thin films with poor crystal quality were obtained for the growth parameters of low substrate temperature or Ga-rich condition. However, the growth at high substrate temperature or N-rich condition formed GaN nanorods structure, and was beneficial to the crystallization of GaN layers with preferential orientation (0001). In the end, the possible growth mechanism of GaN nanocolumns and nanorods was discussed in the letter.