Preparation And Properties Study Of GaN Based Diluted Magnetic Semiconductors

Diluted magnetic semiconductors (DMSs) consist of nonmagnetic semiconducting materials doped with a few at% of impurity magnetic cations of 3d transition metal or 4f rare earth. Due to the incorporation of magnetic ions, DMSs exploit spin in magnetic materials along with charge of electrons in semiconductors. Therefore, DMSs exhibit some novel properties as compared to conventional semiconductors.Much attention is focused on diluted magnetic semiconductor (DMS) materials now. As one of the most promising DMS candidates, transition metals doped GaN has been receiving great attention very recently. Although there have been many inspiring results in both theoretic and experimental fields, there has been a most difficult problem——the origin of the observed ferromagnetism. Therefore, in this work, our attention has been centralized on GaN based DMS. We exploit a two-step method to prepare the samples. First, the preparation of gallium manganese oxide or gallium iron oxide; second, Ammoniating progress.1. Series of GaMnN:Series of GaMnN with different Mn concentration were prepared using the sol-gel method, and the Ga0.95Mn0.05N powder and thin film samples were prepared by the solid-state reaction processes and radio-frequency (RF) magnetron sputtering. No indication of a secondary phase was found in either sample, and all the samples had a hexagonal wurtzite structure. The magnetic properties indicated that the powders prepared by two different methods were paramagnetic at 5 K. From the fitting of Curie–Weiss law, the Curie–Weiss temperatureΘ(x) was evaluated to be negative, and it indicated that there was strongly antiferromagnetic interaction between the nearest Mn ions. However, the paramagntism was observed at room temperature in the Ga0.95Mn0.05N film sample. Ferromagnetism or not at lower temperature in films is necessary to investigate.2. Series of GaFeN:(1) Series of GaFeN thin films were prepared using radio-frequency (RF) magnetron sputtering. All samples had a hexagonal wurtzite structure. X-ray photoelectron spectroscopy results indicated that the doped Fe ions in films were in the divalent state. The Hall Effect measurements confirmed that all the films were n-type semiconductors. The resistivities of all samples increased with Fe content increasing. Magnetic measurements indicated that all films were ferromagnetic at room temperature. The ferromagnetism was not origined from the second phases, but from the intrinsic property of the lattice, which can be explained by bound magnetic exciton polaron model (BMPs). The saturation magnetization decreased monotonously as Fe content increase. The decrease in magnetic moment per Fe ion with increasing Fe concentration could be due to an increased number of Fe atoms occupying adjacent cation positions resulting in antiferromagnetic alignment.(2) Series of GaFeN powder samples were prepared using the solid-state reaction processes. All the samples had hexagonal wurtzite structure measured by X-ray diffraction. Magnetic measurements indicated that Fe doping could induce room-temperature ferromagnetism. But the origin of the ferromagnetism was unclear, and further experiments shloud be necessary in the future.