Cross-sectional transmission electron microscopic observation was performed to understand the behavior of threading dislocations in an AlxGa1-xN layer epitaxially grown on an AlN/α-sapphire (00▪1) template. In the AlN template, threading dislocations with c-component, or c-type and/or (a + c)-type, were annihilated so that most of the threading dislocations remaining in the upper region of the AlN template were of a-type. In an AlxGa1-xN (x = 0) layer grown on the AlN template, pairs of the threading dislocations were annihilated very quickly at or just above the hetero-interface of GaN/AlN. In the case of AlxGa1-xN (x = 0.27, 0.61), threading dislocations penetrate into the AlxGa1-xN layer and some of these were arranged to be tied-up in the region several hundreds of nm from the hetero-interface. The height of the region where threading dislocations were arranged and the number of surviving threading dislocations increase with the Al content x. These phenomena show that the threading dislocations were annihilated by stress due to lattice mismatch between AlxGa1-xN and AlN.

TEM Analysis of Threading Dislocations in Crack-Free AlxGa1-xN Grown on an AlN(0001) Template. N.Kuwano, T.Tsuruda, Y.Kida, H.Miyake, K.Hiramatsu, T.Shibata: Physica Status Solidi C, 2003, 0[7], 2444-7