Speaker
Mr
Noppadon Toongyai
(Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, THAILAND 10330)
Description
The N related vibrational modes (N-RVMs) in high quality GaPN films (0 < N ≤ 5.4 at%) on GaP (001) substrates grown by metalorganic vapor phase epitaxy (MOVPE) have been investigated. This study used two sets of samples with different growth times of 5 min and 10 min. N contents, which were examined from high resolution X-ray diffraction (HRXRD) measurements, are 1.8 at%, 2.9 at% and 3.6 at% for growth time of 5 min and are 0.8 at%, 1.8 at%, 3.4 at% and 5.4 at% for growth time of 10 min. Mirror like surface and fairly flat interface were observed for all the films. Atomic force microscopy (AFM) images showed smooth surfaces with root mean square (RMS) roughness lower than 0.5 nm. These results suggest that the high quality GaPN films with high N contents were obtained, despite the fact that an incorporation of N is as high as 5.4 at%. Raman spectroscopy studies were performed to examine the effect of N incorporation on the vibrational modes of the GaP lattice. It is clearly observed that Raman spectra between 440 and 520 cm$^{-1}$ were significantly influenced by the N incorporation, which is attributed to N-RVMs. Integrated Raman intensity ratio of N-RVMs with respect to GaP-LO phonon (at 401 cm$^{-1}$) linearly increased with the N incorporation. Additionally, the N-RVMs, which are attributed to the NN$_i$-pairs, were remarkably appeared at 465 cm$^{-1}$ and 485 cm$^{-1}$ for the films with N contents higher than 1.8 at%. While, local vibrational mode (LVM) of the isolated N-atoms on P sites was clearly observed near 500 cm$^{-1}$.
Primary author
Mr
Noppadon Toongyai
(Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, THAILAND 10330)
Co-authors
Prof.
Kentaro Onabe
(Department of Advanced Materials Science, The University of Tokyo)
Prof.
Sakuntam Sanorpim
(Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok, THAILAND 10330)
