Backside gate thin film transistor based on MOCVD grown ZnO on SiO2/Si substrates

Zinc oxide (ZnO) is a direct bandgap (Eg= 3.36 eV) semiconductor with a large exciton binding energy (60 meV), exhibiting near UV emission, transparent conductivity and piezoelectricity. It also has comparable to GaN high saturation velocity and better radiation hardness. Furthermore, ZnO is bio-safe and biocompatible, and may be also used for biomedical applications. Because of its unique properties, ZnO has recently attracted strong attention. Its applications vary from sensors and piezoelectric mechanical systems, to optical and electrical components. Interest in transparent displays has prompted a significant increase in studies of thin film transistors (TFTs) [1]. Compared to the widely used amorphous silicon displays, ZnO offers a major advantage in terms of significantly higher carrier mobility and excellent electrical and optical properties [2, 3]. Various reports addressed Metalorganic Chemical Vapor Deposition (MOCVD) grown ZnO layers, but only few results exist on TFTs [e.g. 4, 5]. MOCVD is a well established technique and has already become the dominant process for the manufacture of laser diodes, solar cells, LEDs and transistors. One particular advantage of the use of MOCVD ZnO growth for industry applications is the capability of using large size substrates at a relatively low cost-value ratio.