Coalescence during epitaxial lateral overgrowth of (Al,Ga)N(1 1 .2) layers

Epitaxial lateral overgrowth is reported for semi-polar (Al,Ga)N(1 1 .2) layers. The mask pattern consisted of periodic stripes of SiO2 oriented parallel to either the GaN[1 1 .0] or the GaN[1 1 .1] direction. Lateral growth occurred either along GaN[1 1 .1] or along GaN[1 1 .0]. For growth along the [1 1 .0] direction, coalescence was achieved for layer thicknesses >4 μm. However, planarization was not observed yielding extremely corrugated surfaces. For growth in [1 1 .1] direction, coalescence was delayed by a diminishing lateral growth rate. Growth of AlGaN during ELOG resulted in coalescence. Improvement in crystal quality of such buffer layers for the growth of InGaN/GaN quantum wells was confirmed by X-ray diffraction and photoluminescence spectroscopy.