Electroceramics—the role of interfaces

The opportunities and potential problems in the development of junction-based devices composed of semiconducting oxides are examined. The relevant differences between the material properties of oxide semiconductors and conventional semiconductors are discussed. This is followed by a review of the work done on various kinds of oxide junctions, i.e., metal–semiconductor (Schottky), double Schottky barriers, p–n homo- and heterojunctions and n–n heterojunctions. The use of nanosized structures is expected to play an important role in future junction-based devices, and special attention is given to the situation where the space charge region exceeds the dimensions of the structure. Three important requirements for further developments in this emerging field are identified: (i) selective activation of shallow donor or acceptor states in normally p- or n-type conducting oxides, respectively, (ii) growth of single crystal p–n homo- and heterojunctions, and (iii) improved control of interface states.