| AVS 61st International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Films Poster Session |
| Presenter: | Junichi Iwata, Meiji University, Japan |
| Authors: | J. Iwata, Meiji University, Japan Y. Hirano, Meiji University, Japan H. Sase, Meiji University, Japan H. Katsumata, Meiji University, Japan |
| Correspondent: | Click to Email |
ZnO is an interesting wurtzitic semiconducting material with a wide band-gap of 3.3 eV. It has been reported that the reduction of the optical band-gap down to 2.4 eV was observed from (ZnO)x(GaN)1-x powders with x = 0.81[1]. Moreover, optical band-gap of nitrogen doped ZnO (ZnON) films decreased from 3.26 to 0.9 eV with increasing the N concentration[2], while that of Zn1-xGaxO films was reported to be engineered from 3.3 to 4.9 eV by varying the Ga content[3]. From these facts, we believe that the band-gap of ZnGaON can be widely controllable from 0.9 to 4.9 eV by changing their chemical composition. In these previous reports, however, there have been few observations on their luminescence properties. The purpose of this study is to form ZnGaON thin films with various optical band-gaps. The substrates used in this study were c-axis sapphire substrates or glass substrates. ZnGaON thin films were deposited on these substrates by two kinds of radio frequency (RF) magnetron co-sputtering methods. One is co-sputtering (a) of GaN tablets and a ZnO target in N2/O2 gas flow, in which the GaN tablets were placed on the ZnO target and the number of GaN tablets (NGaN) was varied from 0 to 3. The other is co-sputtering (b) of Ga2O3 tablets and Zn target in Ar/N2 gas flow, in which the Ga2O3 tablets were placed on the Zn target. Samples were subsequently subjected to NH3 treatment at 500 °C for nitridation in former co-sputtering (a) and N2 annealing at 500 °C for improvement of crystallinity in latter co-sputtering (b). These samples were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS), optical transmittance and photoluminescence (PL). First of all, we show the characterization results of films prepared by co-sputtering (a). XRD analysis showed that the crystalline quality of ZnGaON films became worse with increasing NGaN. EDS results revealed that nitrogen doping concentration in ZnGaON films was increased only by NH3 treatment. Optical band-gap of ZnGaON films became wider from 3.29 to 3.51 eV with increasing NGaN from 0 to 3 due to Burnstein-Moss shift. PL spectra of ZnO films showed band-to-band emission at 380nm, while those of ZnGaON films exhibited a broad and weak peak centered at 530 nm, which results from oxygen interstitial (Oi). On the other hands, optical band-gap of ZnON films prepared by co-sputtering (b) without Ga2O3 tablets decreased to 1.18 eV, probably due to formation of Zn3N2.
[1] J. Wang et al., J. Mater. Chem., 21, 4562 (2011).
[2] L. Jensen et al., J. Phys. Chem. C, 112, 3439 (2008).
[3] J. Zhao et al., IEEE Trans Electron Devices, 56, 2995 (2009).