High-temperature formation of highly strained pure-Ge/Si short-period superlattices (SPSs) and their photoluminescence (PL) properties are presented. We grew 99 period SPSs consisting of two-dimensional Ge layers separated by thin Si barriers. The evolution of undulations is newly observed for samples with small Si barrier thickness, which is attributed to a strain-related growth phenomenon, and similarities to the well-established island formation are discussed. Clear band-edge PL is observed in these high-temperature grown SPSs, and interesting PL properties associated with the undulation formation are presented.