We have studied InGaN single-quantum-well (SQW) films using atomic force microscopy (AFM) and cathodoluminescence (CL) spectroscopy. It has been found that a screw dislocations (SDs) distribution in the height image by AFM is well correlated with images of the CL spectra at about 440nm assigned to the spontaneous emission from the InGaN SQW. These results at least mean an existence of non-radiative recombination centers within the InGaN SQW films. It has been also found that the average period of the peak-intensity and the FWHM change is smaller than that of the peak-wavelength change assigned to InN mole fluctuations. These results suggest that the exciton diffusion length of the spontaneous emission at about 440nm is not larger than the average period of InN mole fluctuations in the InGaN SQW.