Sol-gel derived GeO2-doped silica thin films (x)GeO2:(1-x)SiO2 with x = 5 to 40 mol % were studied for heat-treatments from 500 to 1000 degrees C. In the conventional single component sol-gel process, temperature is the process parameter that controls the porosity of the film. However, our results revealed that by varying Ge-doping, the film porosity, as determined by spectroscopic ellipsometry, can be tailored across the temperature range studied. The mechanisms contributing to the quasi-linear compositional-dependent porosity are Ge precursor chemistry and viscous sintering. This technique can be versatile in applications such as III-V optoelectronic devices realized by quantum-well intermixing. (C) 2004 The Electrochemical Society.