MOCVD growth and annealing characteristics of Mg-doped AlGaN films

We investigate the growth of Mg doped AlxGa1-xN films grown by metal organic chemical vapor deposition (MOCVD). The high temperature AlN interlayer can improve the quality of films, reducing the density of dislocations. With the increase of Al composition, the quality of films dramatically decreases, and a large number of island-shaped crystal nuclei can be observed, for three-dimensional growth mode of Mg-doped AlxGa1-xN can not be transformed into two-dimensional mode easily. Both the increase of Al composition and Cp2Mg flux can increase the density of screw dislocations. The increase Of Cp2Mg flux can considerably increase the density of edge dislocations, while the increasing Al composition has little impact on the density of edge dislocations. Finally, annealing at 900 degrees C for 15 minutes after growth is the ideal annealing condition for obtaining p-type Al0.2Ga0.8N, with hole concentration of 1.0x10(17) cm(-3).