Strain control in AlN top layer by inserting an ultrathin GaN interlayer on an AlN template coherently grown on SiC(0001) by PAMBE

We propose partially relaxed ultrathin GaN interlayer for strain control of AlN on SiC substrates. According to the degree of relaxation of the GaN interlayer, the lattice constant of the interlayer changes from that of SiC to that of bulk GaN, which leads to strain control of an AlN top layer grown on the interlayer. Growth of these layers is conducted by plasma-assisted molecular beam epitaxy. Before growing the interlayer, an AlN layer coherently grown on SiC is used as a template layer. The interlayers that have different degrees of relaxation are successfully obtained by changing the interlayer thickness. As a result, strain values of the AlN top layer grown on the interlayers are widely controlled from compressive (-0.53%) to tensile (+0.07%). TEM observation revealed the relaxation is induced by U-shaped half-loop dislocations originating from the GaN interlayer. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim