| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM-ThP |
| Session: | Electronic Materials and Photonics Poster Session |
| Presenter: | Kosala Yapabandara, Auburn University |
| Authors: | K. Yapabandara, Auburn University V. Mirkhani, Auburn University S. Wang, Auburn University M.P. Khanal, Auburn University S. Uprety, Auburn University M.H. Sk, Qatar University, Qatar A. Ahyi, Auburn University T. Isaacs-Smith, Auburn University M.C. Hamilton, Auburn University M. Park, Auburn University |
| Correspondent: | Click to Email |
ZnO has been widely studied due to its promising material properties as a wide energy bandgap semiconductor, optical transparency, and high carrier mobility for thin film transistor (TFT) technology. Solution-based ZnO can easily be deposited on large areas of substrates at low temperatures, which makes this material a good candidate for commercial device manufacturing. Moreover, ZnO exhibits a higher radiation hardness compared to semiconductors such as Si, GaAs, and GaN. However, it is not entirely understood why ZnO shows superior radiation hardness over GaN.
In this work, we report the device performance analysis of solution derived ZnO TFTs upon irradiation of 100 keV proton with 1014 cm-2 fluence. A comprehensive analysis of unirradiated and irradiated samples was performed to elucidate the proton irradiation effect on ZnO TFTs. The room temperature photoluminescence analysis showed a slight reduction in intensities of near-band-edge UV peak and visible luminescence band while the peak positions and the full-width half maximum (FWHM) are unchanged upon irradiation. This implies that negligible damage has occurred in the ZnO channel layer due to the proton irradiation. From transfer characteristics analysis, it was observed that the reduction in the drain current (ID ) at high drain-source voltages (VGS) regime is less than an order of magnitude, which also suggests minimal irradiation damage to the ZnO lattice. However, the shift in VON and an enhancement in subthreshold swing (SS) after the proton irradiation were observed, which is believed to be produced by radiation-induced electron-hole pair production in the SiO2 layer. Multiple peaks in incremental mobility (µinc) variation with VGS and a plateau in low-frequency C-V curve were observed in unirradiated samples. A model was proposed to explain these abnormalities. It is reasonable to think that a significant number of defects is introduced into sol-gel derived ZnO channel during the deposition process. Since our deposition process requires more that one spin coating run, ZnO-ZnO interlayer interfaces will be formed. It was hypothesized that the depletion regions are created by oxygen-related trap centers at the ZnO-ZnO interlayer interfaces. It was conjectured that the disappearance of multiple peaks in µinc and the plateau in low-frequency C-V curve upon proton irradiation might be the result of the reduction of the depletion layer in the proximity of ZnO-ZnO interlayer interface.