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

This paper reports the successful growth and characterization of thin film transistors based on MOCVD (metalorganic chemical vapor deposition) grown ZnO with best so ever reported performance. Highly conducting (<;0.01Ωcm) p-type (111) silicon substrates were used to achieve a low resistive backside gate. A thin, 20 nm dielectric SiO₂ layer was then deposited by PECVD. A modified Aixtron 200/4 MOCVD system was used for depositing the channel layer. Different growth temperatures (450°C, 650°C and 750°C) were used for growth in order to investigate their impact on device characteristics. Oxygen (99.9999 %) and DEZ (bath temperature 30°C) were used as precursors, while the carrier gas was selected to be nitrogen. A 50 nm thick ZnO was then deposited on top of the SiO₂. The ZnO thickness was monitored by calculating the the growth rate using a homemade in-situ interferometry system. A thick ZnO layer was used as calibration run. The growth rate for the ZnO was found to be ~2 μm/h.