ZHU You-zhang, CHEN Guang-de, YUAN Jin-she. Investigation on Optical and Micro-structural Properties of In<sub>x</sub>Ga<sub>1-x</sub>N Alloys Grown by MOCVD[J]. Chinese Journal of Luminescence, 2008,29(2): 318-324
ZHU You-zhang, CHEN Guang-de, YUAN Jin-she. Investigation on Optical and Micro-structural Properties of In<sub>x</sub>Ga<sub>1-x</sub>N Alloys Grown by MOCVD[J]. Chinese Journal of Luminescence, 2008,29(2): 318-324DOI:
Investigation on Optical and Micro-structural Properties of InxGa1-xN Alloys Grown by MOCVD
The photoluminescence (PL) and photoluminescence excitation spectra (PLE) of selected In
x
Ga
1-x
N samples grown by metal organic chemical vapor deposition (MOCVD) have been investigated
and the analysis of structural and optical behaviors has been taken to study the existence of the microstructure InGaN alloys on the basis of X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements.XRD reveals that the sample is a single crystalline In
x
Ga
1-x
N film formed predominantly in (0002) direction
the In mole composition x in In
x
Ga
1-x
N film is calculated to be about 0.2 according to the Bragg's angle of In
x
Ga
1-x
N (0002). The AFM plane-view and 3D images of the selected In
0.2
Ga
0.8
N sample show almost uniform island-like microstructure appearing to be composed of granular-crystalline in nanometer scale. The islands composed of the grapes-like have an average height of 10 nm at most and a mean size of 300 nm. The self-organized microstructure appeared to form cone and/or pyramid shape and tended to agglomerate island-like surface with RMS roughness about 10 nm
which attributed to Stranski-Krastanov growth mechanism. The comparison between PLE and PL under different exciting or monitoring energy allows determining the existence of wetting layer (WL)in the sample. The PLE and PL measurements show that the resonant absorption is related to the band gap and wetting layer of the alloy at different exciting and monitoring energy. It has been found that PLE peaks of the In
0.2
Ga
0.8
N alloy are dominated by 365 nm and 474 nm with monitoring wavelength 545 nm and 493 nm; the broad 545 nm and narrow 493 nm emission peaks are originated from In(Ga)N wetting layer and InGaN region respectively. The structural and optical analyses suggest that the origin of the exciton localization center is the self-formed islands. Hence
the irrelevancy of the PL spectra to the gap energy was explained in terms of fluctuation resulting from variations in grain size or shape. This type of localized center provides another physical model for the proposed localized states in In
x
Ga
1-x
N epilayers. Further characterization of the InGaN systems is underway to help fully understand the correlation between the structural and the optical pro-perties of self-organized micro-structure of InGaN system.
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