Is there any database listing the experimentally-determined properties of semiconductor materials - things like Band Gap and Electron Mobility. These are easily found for common materials like Germanium or Gallium Arsenide. But what databases have systematic lists properties for materials which are currently being researched (preferably by type, such as $\ce{ABX2}$).
These might prove very useful for computational studies (particularly Machine Learning approaches), as well as excellent references for characterization of synthesized materials.