The Preparation And Properties Researches Of GaN Nanoparticles

Gallium Nitride (GaN) is a wide band gap semiconductor material. It has a direct band gap of 3.4eV at room temperature, and exhibits good chemical stability, high thermal conductivity and high saturated electron mobility. GaN has been regarded as one of the most promising materials for blue, near ultraviolet optoelectronic devices, and it also can be applied to high power and high temperature microelectronic devices. Studies of GaN have attracted much interest of many research workers in recent years due to its wide potential use for such more applications. When the single components of the devices reach nano-scale, they exhibits different and potentially better optical and electrical properties compared to the bulk materials. So it is necessary to study the properties of low dimensional materials for their potential applications.For low dimensional semiconductor materials, electron and phonon are the two important particles that take great part in their electrical, optical properties. As the size reduced to phonon wavelength scale, the phonon confinement in the devices may occur. The red-shift of Raman spectra related to the phnon confinement has been explained quantificationally by physical model. However, the blue-shift of IR spectra related to the phnon confinement has not been explained quantificationally. In this paper, we have prepared the Ga₂O-3 capped GaN nanoparticles and Ga₂O₃-GaN-Ga₂O₃ nanoparticles and studied quantificationally the phonon confinement related to blue-shift of IR spectra based on the red-shift of Raman spectra.First, the amination of Ga₂O₃ powders are studied and the preparation parameters were obtained. Second, the Ga₂O₃ capped GaN nanoparticles are prepared by pure GaN powder annealed at 800℃ for different reaction time. Third, we synthesized the core-shell-like Ga₂O₃-GaN-Ga₂O₃ nanoparticles. Pure Ga₂O₃ powders were placed in a quartz boat under high temperature of 900 ℃ and ammonia circumstance. And then, the samples were annealed at 800 ℃ for different time. Finally, we studied the effect of the surface tension in the GaN IR spectra. 1, It indicates that the optimal condition of synthesizing GaN powder is to aminate Ga₂O₃ at 900 ℃ for 90min with the NH₃ flowing rate of 100sccm. From the XRD patterns when the reaction time exceeds 60min, the peaks of GaN have no changes. But the XPS patterns indicate that the stoichiometric ratio of Ga to N at the surface of our samples is 1: 1 when reacted for about 90min. That is to say, to prepare GaN powder with ideal stoichemical ratio we should accurately control the reaction temperature and the reaction time. In this paper, we consider that it is reasonable for Ga₂O₃ animating at 900 ℃ for 90min and NH₃ flowing rate of 100sccm.2,According to the TGA result, we choose 800℃ as the reaction temperature. XRD showed the Ga₂O₃ capped GaN nanoparticles were prepared. Raman spectra showed the peaks of GaN had a red-shift as the reaction time increased. It can be attributed to the decrease of the particle size of the GaN. The IR spectra showed a blue-shift of GaN peaks.3,The core-shell-like Ga₂O₃-GaN-Ga₂O₃ nanostructure were prepared. First, GaN powders were aminated for 25min at 900℃ and then annealed at 800℃ for 5min, 8min, 10min, 12min and 15min. The XRD and FTIR spectra indicated the formation of Ga₂O₃-GaN-Ga₂O₃ nanostructure.4,According to the red-shift of raman spectra, we estimated the size of the Ga₂O₃ capped GaN nanoparticles annealed for different times(15min,25min,45min), is 8.9nm, 6.3nm and 4.5nm respectively. We also studied the relation of blue-shift of IR spectra and GaN particle size. It indicated that the surface tension take a great part in the IR spectra.