Chemical mapping and formation of V-defects in InGaN multiple quantum wells

InGaN multiple-quantum-well structures grown by metal-organic chemical-vapor deposition on GaN and capped by p-type GaN are found to contain inverted pyramids of indium-free GaN. High-resolution structural and chemical analyses of these "V-defects" by a number of complementary transmission electron microscopy techniques show that the InGaN quantum wells end abruptly at the V-defect interfaces, which lie on {10-11} planes. Each V-defect has at its center a threading edge dislocation, indicating that the defects are initiated at edge dislocation cores in the presence of indium. The lower temperatures of InGaN/GaN quantum-well growth (790 degrees C/950 degrees C) assist the formation of V-pits, which are subsequently filled in during the growth at higher temperature (1045 degrees C) of the p-type capping layer. (C) 2000 American Institute of Physics. [S0003-6951(00)00335-1].