It is well known that silicon-rich oxide (SRO) shows intense photoluminescence (PL). In this work, the authors studied the relationship of the surface morphology and the PL emission. PL spectra of SRO as a function of the excess silicon, temperature, and time of thermal annealing were obtained. The same samples were studied using transmission electronic microscopy and atomic force microscopy to determine their microstructure and surface morphology. A relationship between silicon agglomerates in the SRO and the surface morphology was obtained. Then, the red PL emission was related to the surface morphology. The authors found that the surface roughness is an important parameter for the high red emission of SRO.