ZnO is a wide band gap semiconductor with potential applications to optical emitters due to its very high emission intensity and large exciton binding energy (~60 meV) which persists even at room temperature. In addition, unlike GaN, bulk ZnO substrates with very high quality are available. The bottleneck, however, has been the unambiguous attainment of p-type conductivity. In the interim period, heterojunctions of ZnO with other semiconductors with p- type conductivity are used to demonstrate the potential of this material. In this presentation, growth by MBE, and electrical and optical properties of ZnO/GaN and ZnO/SiC heterojunctions inclusive of band discontinuities will be discussed. In addition, preparation and optical properties of ZnO nanowires will be presented. |