Crystal quality and conductivity type of epitaxial (002) ZnO films on (100) Si substrates for device applications

Zinc oxide is a wide band-gap (3.37eV) semiconductor with high exciton binding energy (60meV) and excellent piezoelectric properties, showing promise for UV lasers, optical detection, sensors, and solar cells. Epitaxial growth of ZnO on Si is challenging due to lattice mismatch and thermal expansion coefficient differences, but it is important to develop such film growth in order to enhance the functionality of Si and provide optoelectronic and gas sensing capabilities in CMOS based ICs. Furthermore, ZnO grown by most techniques is nominally ntype and p-type films are hard to achieve; hampering the development of p-n junction devices.