The Growth And Characterization Of AlN Buffer Layer And P-type Al_0.55Ga_0.45N

?-nitrides have become one of the most prominent compound semiconductors due to their merits such as wide band gap and high saturated electron drift velocity.Compared with GaN and In N,AlN has obvious advantages in terms of its widest band gap and stability.But the method of AlN growth is different from GaN growth.Pre-reaction and growth temperature would affect crystal quality and surface morphology.In addition,compared with p-type doping in GaN,p-type doping of AlN and AlGaN becomes more difficult due to the influence of the activation energy of Mg and the formation energy of nitrogen vacancy.In this Dissertation,the properties of AlN-based materials have been studied.The main contents of our research are summarized as follows:1.The growth of high temperature AlN buffer layer with different ?/? ratio by MOCVD have been studied.The AlN films with different ?/? ratio grows in island mode.X-ray diffraction results reveal that crystal quality becomes better with high ?/? ratio,but surface becomes rough due to the formation of large AlN island.2.The surface morphology and electrical property of p-type Al_0.55Ga_0.45 N have been measured.Magnesium is used as p-type dopant.X-ray diffraction was used to determine the Al content with the help of simulation software.Surface roughness of the samples was obtained using an atomic force microscope.With the increasing of Mg concentration,surface roughness presents a trend of increasing first and then decreasing.Four-point probe method shows that Al_0.55Ga_0.45 N transforms from n-type to p-type by involving Mg.The resistivity increases with Mg concentration at first.When the sample is p-type,the resistivity begins to decrease.When Mg atom concentration is high enough,leading to the decrease of ionized Mg atoms,the electrical resistivity will decrease correspondingly?In conclusion,AlN epitaxial layers growing in different ?/? ratio have been studied.Moreover,p-type Al_0.55Ga_0.45 N with various Mg concentration have been tested.The regularity of their surface morphology and resistivity have been got by XRD and AFM.