Growth temperature effects on In _x Ga _{1 - x} N films studied by X-ray and photoluminescence

The InGaN films were grown between 850°C and 600°C by the metalorganic chemical vapor deposition method and characterized by X-ray diffraction and photoluminescence (PL). The incorporation of In into the ternary films was found to increase from x = 0.01 to 0.28 as the temperature decreases. In films grown at 750°C and higher, both the X-ray and PL results show gradual changes and indicate 5% In molar fraction difference that may be due to the alloy composition fluctuation. However, in films grown at 700°C and lower, the near band edge emission disappears and the impurity transitions (IT) become dominant in the PL spectra, in contrast to X-ray diffraction where the line width broadens sharply from less than 300 arcsec to larger than 500 arcsec. We also found that IT is relatively insensitive to the sample temperature. Besides, the correlation between enhancing PL intensity and patterned micro-structure is observed.