Growth Of GaN Films Or AlN Films On Freestanding Diamond Substrates By ECR-PEMOCVD

The freestanding thick diamond films combine the highest elastic stiffness coefficient and the excellent performance of maximum speed of sound; it is a reasonable substrate material with the SAW filter, which can avoid the problem of the poor heat than that of other substrates. The structure of piezoelectric film/freestanding thick diamond films can only use the piezoelectric film with excellent piezoelectric properties and freestanding thick diamond films with excellent properties of maximum speed of sound, but also make full use of both high thermal conductivity and excellent heat resistance advantage. Therefore, this structure can be the ideal material for preparing the high-frequency and high-power SAW filter. In this study, the piezoelectric films of high quality with good performance and application requirements were prepared on freestanding diamond thick films by the method of this process, which lays a good foundation for further device fabrication and application.In this study, the GaN and A1N films were prepared on the freestanding diamond thick films using by ECR-PEMOCVD system, which mainly through the theme "how to achieve the high quality piezoelectric films with good performance" to carry out the research work.The conclusion as following:1, The GaN piezoelectric film was prepared on freestanding diamond thick films by ECR-PEMOCVD.(1), The deposited temperature plays a important role for the quality of as-grown films, when the deposited temperature is400℃, the as-grown is of the good crystalline quality with the high C-axis oriented growth. The surface morphology of the sample is very smooth, which meets the requirements of the SAW device. Optical and electrical properties of the samples were tested, the results show that the as-grown films have excellent optical and electrical properties.(2), The GaN films were prepared with various TMGa flux and the properties of the as-grown films were investigated. When the TMGa flux is0.5sccm, the as-grown film is of the high quality with the high oriented growth and smooth surface morphology.(3), The GaN films were prepared with various N2flux and the properties of the as-grown films were investigated. When the N2flux is100sccm, the as-grown film is of the high quality with the high oriented growth and smooth surface morphology. The electrical properties of as-grown films were very excellent.(4), The buffer layer plays an important role for the quality of as-grown films, the GaN films were prepared with various buffer layer process and the properties of the as-grown films were investigated. The results show that when the deposition temperature of the buffer layer is proper, the as-grown film is of the high quality with the high oriented growth and smooth surface morphology.2, The A1N piezoelectric film was prepared on freestanding diamond thick films by ECR-PEMOCVD.(1), The deposited temperature plays a important role for the quality of as-grown A1N films, when the deposition temperature is too high or too low, it is not conductive to deposit the as-grown films. When the deposited temperature is400℃, the as-grown is of the good crystalline quality with the high C-axis oriented growth. The surface morphology of the sample is very smooth, which meets the requirements of the SAW device.(2), The N2flux plays a important role for the quality of as-grown A1N films, and the N2flux directly affect the quantity of the reactivity N-particle. When the N2flux is proper, the as-grown films is of the high-quality and high-preferred orientation as well as the smooth surface morphology. And we investigate the composition of the samples, the results show that the N content is high, which is due to the the N vacancies and the Al/N atomic percentage has a large effect on the quality of the as-grown films. We investigate the electrical properties of as-grown films, and the results show that the as-grown films have the high impedance.The experimental results show that deposition temperature, reaction source flux as well as buffer layer process are very important for depositing the as-grown films and the process of the as-grown piezoelectric films deposit on freestanding thick diamond films is very strict, which is affect on the quality of as-grown films with a slight change. The high-quality as-grown films have been prepared on the freestanding thick diamond substrate, and the piezoelectric film of high quality has a significant role to improve the frequency of the SAW devices.