  Appropriately designed transition metal oxide heterostructures involving
small band gap Mott insulators are argued to support spatially separated
electron and hole gasses at equilibrium. Spatial separations and carrier
densities favoring the formation of excitonic states are achievable. The
excitonic states may exhibit potentially novel properties. Energetic estimates
are given, candidate material systems are discussed, and the possibility of
large photvoltaic effects is mentioned
