Measurements And Characterizations Of AlGaN Epitaxial Layer With High-Al Concentration

High Al component AlGaN epitaxial layers of high crystalline quality are of great importance for the fabrication of short-wave devices such as light emitting diode ,laser diode and ultraviolet photodetector. Therefore, the characterization of epitaxial layer by means of all kinds of measurement technologies, which provides theoretical basis for subsequent MOCVD growth,is also of great significance.Rutherford backscattering spectrometry(RBS), high resolution X-ray diffraction(XRD), Scanning Electron Microscope(SEM), Transmission Electron Microscope (TEM), Atomic Force Microscope(AFM) and other measurement technologies are used to study the AlGaN epitaxial layers. Wet etching by molten KOH is also used. According to the experiment results, these results are got:1. Rutherford backscattering technology is an effective way to determine the component in solid solution. But for the sample of complicated structure, using this method will increase the difficulties of fitting even get the result which has large difference from actual component.2. It is known that the inserting of superlattice will regulate stress and filer dislocations effectively, which is based on flat superlattice structure. The superlattice structure will become new dislocation source and decrease crystalline quality if the superlattice structure is not flat, which is caused by other factors. The quality of AlN buffer is of great importance to subsequent growth and surface topography. Therefore, it is important to introduce monitoring devices.3. The etching results show that all the samples with different qualities have different polar directions. The main reason for the formation of different polar direction is the inhomogeneous nitridation of sapphire substrate which has both N-polarity and Al-polarity. The result provides basis for the optimization of nitridation.4. The formation of different surface topographies is revealed, which provides basis for avoiding the analogue problem and the optimization of growth.