Preparation Of Al-N Codoped Zn_1-xMg_xO Thin Films With Different N Source And Its Property Researches

ZnO is an II-VI compound semiconductor with a wide direct bandgap of 3.3 eV and a large exciton binding energy of 60 meV at room temperature. In order to realize ZnO-based short-wavelength optoelectronic devices, one of the critical issues is to obtain stable p-type doping; the other is the modulation of bandgap of ZnO. Recently, codoping method provided by Yamamoto is a new approach for high-quality p-type ZnO thin films. And by doped with Mg, the bandgap of ZnO can be modulated in a wide range from 3.3 eV to 4.0 eV, and still maintain a hexagonal wurtzite structure. Because of high resistivety of Zn_1-xMg_xO thin films, the fabrication of high-quality p-type Zn_1-xMg_xO thin films with low resistivity is more difficult.In this paper, Al-N codoped p-Zn_1-xMg_xO thin films were deposited on glass and single crystal n-Si (111) substrates by DC reactive magnetron sputtering, by using NH₃ and N₂O as N source, respectively. Our work is as below:Adopting NH3 as N source, we prepared Al-N codoped Zno.95Mgo.05O thin films at the different substrate temperature. When the substrate temperature is 500 °C, as-grown thin film has a better crystal quality, and definitive p-type conduction, with a hole concentration of 1.23×10¹⁷ cm^-3, a Hall mobility of 0.41 cm²/Vs and a resistivity of 171 Ωcm. By doping with Mg, the bandgap of ZnO thin films has been modulated regularly. And we found the electrical properties of Al-N codoped p-Zno.9Mgo.1O thin films are better than j9-Zno.95Mgo.05O. So we deposited the p-Zn_0.9Mg_0.1O thin films on the single crystal n-Si (111), I-V characteristics of p-Zn_0.9Mg_0.1O/n-Si heterojunction shows good rectify characteristics, and low current leakage under bias voltage.Adopting N₂O as N source, we prepared Al-N codoped Zn_0.95Mg_0.05O thin films under different N₂O partial pressure ratios at 500℃. When the N₂O partial pressure ratio is 0.7, as-grown thin film has better c-axis preferential orientation, and an optimal p-type conduction, with a hole concentration of 6.04×10¹⁷ cm^-3, a Hall mobility of 0.619 cm²/Vs and a resistivity of 95.6Ωcm.The transmittance spectra reveal a distinct blue shift between Al-N codoped Zn_0.95Mg_0.05O and undoped ZnO thin films.By annealed in the oxygen ambient, Al-N codoped Zn_0.9Mg_0.1O thin films exhibited a better crystalline structure and their p-type electrical properties got improved effectively, theirhole concentration increases from 5.93×10¹⁵ cm^-3 to 2.84×10¹⁸ cm^-3, and Hall mobility increases from 0.133 cm²/Vs to 0.568 cm²/Vs. Besides, we note that the p-type behavior of Al-N codoped Zno.9Mgo.1O thin films is very stable.