Formation of V-shaped pits in InGaN/GaN multiquantum wells and bulk InGaN films

InGaN/GaN multiquantum well structures and bulk InGaN films grown on (0001) sapphire substrate were investigated by cross-sectional transmission electron microscopy and double crystal x-ray diffraction. Highly strained InGaN layers with a high In mole fraction were found to contain V-shaped surface pits with (10–11) facet planes on pure or mixed screw treading dislocations. Phase separation was also found on thick InGaN/GaN superlattices and bulk InGaN layers. The mechanism of the surface pit formation was discussed in terms of strain energy and surface mobility of InGaN.