Minority Carrier Diffusion Length in AlGaN: A Combined Electron Beam Induced Current and Transmission Microscopy Study

Combined electron beam induced current and transmission electron microscopy measurements have been performed on both undoped and Si-doped AlGaN epitaxial films with aluminium contents x ranging from x=0 to x=0.79. TEM analysis shows the distribution and type of structural defects, the content of cubic phase and the decomposition phenomena strongly to depend on the Al content of the layers. The influence of the cubic phase on the electronic properties of the samples is discussed taking into account the high piezoelectric effect present in these alloys. The diffusion length of minority carriers has been determined by EBIC measurements and a lower limit of the lifetime has been estimated.