The Preparation And Properties Of The Rare Earths-Doped Wide Bandgap Nitrides Semiconductor Films

Rare earths (REs)-doped wide bandgap semiconductor materials have very high intensityand pure color emission with the potential applications in optical communications and fullcolor display. Therefore, doing research on those materials has important theoretical value andapplication prospect.In this dissertation, the structure, optical and electrical properties of the REs-undoped anddoped nitrides (GaN and Zn₃N₂) thin films , which were prepared by direct current magnetronreactive sputtering (DCMRS), were studied. The results are listed as follows:1. Nanocrystalline GaN thin films with controllable crystal size were obtained byDCMRS. As the substrate temperature increases, the growth rate first increases then decreases,the optical band gap decreases from 4.99 to 4.68eV, and the band emission shows blueshift.Theâ… -â…¤characteristic of the p-Si/n-GaN can be understood in terms of thermionic emissionand tunneling emission mechanism. The activation energy and capture cross section of the traplevel was quantificationally analyzed by Q-DLTS.2. Ammonization method was used to prepare nanocrystalline GaN thin films and theoptimum condition was determined at 950℃for 1 h. Two photoluminescence peaks located at365 and 431nm, which are related to the band emission and V_Ga-related complex emission, respectively,are observed at room temperature. Two new additional Raman peaks at 257 and 423cm^-1, which are forbid by the C_6v⁴ space group, are observed. Those two peaks are attributed tothe M symmetric point of E₂ optical branch at zone-boundary phonon and the vibration modeof N-rich octahedral Ga-N₆ bonds, respectively.3. In-situ Er and Tb doped nanocrystalline GaN thin films were prepared by optimizing theparameters of DCMRS. The optical band gap of the films is 4.1～4.3 eV. Photoluminescenceresults show that the films exhibit the characteristic peaks of Er³⁺ and Tb³⁺ correspondingto intra-4f transitions of ⁴S_3/2(²H_11/2)→⁴I_15/2 (554nm) and ⁵D₄→⁷F_J(J=6,5,4,3), respectively.Only two Raman peaks corresponding to E₂(low) and A₁(LO) models of wurtziteGaN appear independently of sputtering parameters such different substrate temperature and sputtering pressure.4. In-situ Tb doped Z113N2 thin films were prepared by DCMRS. As the sputtering N₂concentration increases from 20% to 60%, the preferential growth direction changes from (321)to (222), the indirect optical bandgap decreases from 3.06 to 2.13eV. Only the film grown inthe N₂ concentration of 40% presents four characteristic peaks of Tb³⁺. By fixing the N₂concentration at 30%, the film grown at 200℃shows the highest crystalline and PL intensity ofthe peaks of 4/ transitions of Tb³⁺. As the annealing temperature increases, the films changefrom cubic Zn₃N₂ to wurtzite ZnO, and the intensity of visible emission increases.