Low-dislocation-density AlxGa1−xN single crystals grown on grooved substrates

We propose a new approach to the direct growth of low-dislocation-density AlxGa1−xN single crystal films on highly mismatched substrates. Four different substrates, basal-plane sapphire (0001) and (112̄0), 6H–SiC(0001)Si and Si(111), were used. The surface of the substrates was patterned with periodic grooves. In this technique, neither a selective growth mask nor a patterned GaN single crystal film were used. Low-dislocation-density areas were observed above the trench area and at the boundaries of the terrace and trench areas. The dislocation density was reduced to mid 106 cm−2 which is lower than that of the films grown directly on the planar substrates by at least two orders of magnitude.