Recent advances in detector fabrication and passivation technology have led to the realization of high performance germanium photodiodes with improved reliability suitable for use in optical radiometric measurement applications. Among the most significant accomplishments are the development of planar devices via ion implantation; the effective use of activation anneal and damage removal schemes; and the successfull application of plasma enhanced chemical deposition of oxynitride films in surface passivation. Several key parameters are used to measure the enhancement of the radiometric quality of the device. These include spectral external and internal quantum efficiency, long term stability of the responsivity and the dark current, and spatial uniformity across the active area. Finally, experimental results are compared with theoretical calculations leading to recommendations for further optimization of germanium photodiode performance.