Study of GaN-Mn Growth on Silicon Substrate using Plasma Assisted Metal Organic Chemical Vapor Deposition Method

In this paper the growth and characterizations of semiconductor ferromagnetic GaN-Mn thin films on silicon substrate using PA-MOCVD method are reported. Semiconductor ferromagnetic or DMS (diluted magnetic semiconductor) is synthesized by incorporating a magnetic element (impurity) into a non magnetic semiconductors, in a similar way to doping process. In the case of GaN-Mn, the maximum Mn concentration that would still produce single crystal phase increases with decreasing growth temperature. However, in a thermal MOCVD growth of GaN-Mn, high growth temperature is required to incorporate Mn into GaN in order to achieve ferromagnetism characteristic of the grown films. The PA-MOCVD used in this research, utilizes a microwave cavity as a cracking cell to produce nitrogen radicals, which in turn reduce the growth temperature. TMGa (trimethyl gallium), CP2MnT (cyclopentadienyl manganese tricarbonyl) and ultra high purity nitrogen gas were used as Ga, Mn and N sources, respectively, while hydrogen gas was used as carrier gas. The GaN-Mn films were grown on silicon substrates (111) at varied growth temperature in the range of 625 - 700 oC. The investigation were emphasized to the Mn incorporation mechanism related to the growth parameters and to study the surface morphology, structural and magnetic characteristics of GaN-Mn thin films. The results of EDX analysis reveal that Mn incorporation into GaN depends on growth parameters. While SEM images show that the film grown at higher temperature has a better surface morphology than that of film grown at lower growth temperature. The higher Mn concentration also shows the better surface morphology of the film. A systematic XRD analysis reveal that sample #8.2 with 1.28 % of Mn concentration shows a peak diffraction at 2θ = 32.4 o which indicates single phase orientation of GaN-Mn (100). The results of magnetization measurements using VSM method show hysteresis behavior at room temperature indicating that all of the grown films are ferromagnetic. Sample #2.2 with 1.63 % of Mn concentration shows the highest remanense magnetization (330 Oe/cm3) and lowest magnetic coercivity (180 Oe) which is suitable for device's application. (author)