Sapphire substrate material growth of high quality AlN
|School||Huazhong University of Science and Technology|
|Keywords||AlN The buffer layer Epitaxial layer Crystal quality Surface morphology|
Ⅲ nitride its excellent characteristics have been widespread concern , AlGaN material system corresponding emission wavelength at 210-340nm, fit can be applied to white lighting , biochemical detection, disinfection and purification fields of ultraviolet light-emitting devices become a research hotspot. The AlGaN material, due to the lack of single crystal , the general growth of AlN as a template . Therefore, to obtain high-quality production of the device for AlGaN materials, preparation to become high-quality AlN material must first be solved. Heteroepitaxial AlN films , often using SiC, Si or sapphire as a substrate material . The AlN and these materials do not match, the crystal quality is poor. This paper focuses on the growth of high quality AlN materials commenced a two-step growth method , the main parameters of the buffer layer growth of epitaxial layers . First, the principle elaborated MOCVD growth , characterization used in this experiment equipment HR-XRD, AFM , etc., and data processing methods . According to the material properties of AlN , analyzing substrate selection, surface preparation , reaction chamber pressure , V / III ratio on the growth of AlN , determine the relevant growth parameters . Then explore the buffer layer growth temperature on the crystalline quality of the epitaxial layer and the surface morphology . At 600 ℃ ~ 870 ℃ range selected six samples grown at different temperatures , while keeping other growth parameters unchanged. With transmission spectra , AFM, HR-XRD and other testing , found in the 690 ℃ ~ 780 ℃ when the surface atomic steps, especially in the 780 ℃, the crystal quality is better . Low temperature , the dislocation density ; high temperature , surface roughness , there are many pits . Further changes to the buffer layer growth time to study the effect of the thickness of the buffer layer . Three samples grown , the growth time of 4.4 minutes, the sample ( 0002) FWHM of 116arcsec, (1012) plane FWHM of 1471arcsec, and the surface atomic steps . The thick epitaxial layer is thinner , the surface steps were not there , the crystal quality and surface morphology were poor. According to results of these two experiments , the buffer layer of the epitaxial layer of the mechanism . Finally, the growth of the previous experiment template better , growing a high temperature continuous manner using AlN. Through two experiments , at different growth temperatures , changing TMAl and NH3 flow rate , V / III ratio to the preliminary study on the continuous growth mode AlN quality.