Structural defects due to interface steps and polytypism in III-V semiconducting materials: A case study using high-resolution electron microscopy of the 2H-AlN/6H-SiC interface

A procedure based on the stacking sequences of semiconducting materials structures is proposed in order to determine the possible dislocation character of the interface steps between two different polytypes. It is next applied to the interface between the 2H and the 3C, 4H and 6H polytypes. Three different possible dislocations are found with 1/6 <[20(2)over bar 3]>, 1/3 <[10(1)over bar 0]> and 1/2 [0001] Burgers vectors. In a high-resolution electron microscopy study of the particular case 2H-AIN/6H-SiC, only two kinds of interface step could be observed. This is in agreement with the assumption that the growth of AIN systematically starts at the wurtzite position on the surface of the substrate. One kind of interface step is observed to generate systematically an extended defect in the ALN layer which folds from the basal to the prismatic plane. Although the prismatic defect is not seen edge on, a careful study by image simulation allows one to identify a 1/2 <[10(1)over bar 1]> fault vector contained in the fault plane. The formation of such a defect is related to the growth mode of AIN on alpha-SiC.