Poster: The Development of ZnO, Ultraviolet, All-Optical Switches

The pursuit of high-speed communication has driven the development of new optoelectronic components, such as all-optical, surface-normal, switches constructed of semiconductor thin-film heterostructures. ZnO is a promising material for switches that operate in the ultraviolet (UV) region. It has a bandgap of ~3.4 eV and is less toxic than other materials with similar bandgaps, such as GaN. The structures we are studying are composed of alternating layers of polycrystalline ZnO and Zn_0.9Mg_0.1O, where the ZnO serves as the active semiconductor layer. In these experiments, we measure the absorption changes as a function of the energy, polarization, repetition rate, and time delay of the control and signal pulses. Our experiments indicate that the switching action is produced when the conduction-band electrons and valence-band holes excited by the control separate due to a built-in electric field in the ZnO layers. The resulting space-charge field screens the built-in field, blue shifting the band edge by reducing the excitonic red shift associated with the quantum-confined Stark effect. In our presentation, we will discuss how the carrier dynamics impact the switch’s speed.