Optical transitions and radiative lifetime in GaN/AlN self-organized quantum dots

We present a theoretical study of the optical matrix elements and radiative lifetime for the ground state optical transitions in GaN/AlN quantum dots (QD). An efficient plane-wave expansion method is used to calculate the energy levels, wave functions, and optical matrix elements in the framework of a multiband k.p model taking account of the three-dimensional strain and built-in electric field distributions for QDs with a hexagonal truncated-pyramid shape. We demonstrate that the built-in electric field determines the energy spectrum of GaN/AlN QDs and leads to a dramatic decrease in the optical matrix element with increasing QD size. As a result, the radiative lifetime for the ground state optical transition increases strongly with QD size. The theoretical results obtained are in good agreement with available experimental data. (C) 2001 American Institute of Physics.