By controlled annealing of small ZnSe mesas with embedded CdZnSe quantum dots at considerably low temperatures, significant changes of the quantum dot luminescence were observed. To investigate the spectral evolution of single exciton lines several thermal annealing steps were performed successively, and large energy shifts of single exciton (X) lines due to annealing were traced. In annealed quantum dots the bi-exciton (XX) emission was drastically enhanced. Bi-exciton binding energies less than 10meV were recorded for the thermally annealed CdZnSe QDs, indicating a considerable change in the quantum dot confinement. The pronounced energy shifts of the quantum dot luminescence was attributed to the Cd–Zn interdiffusion between the CdZnSe quantum dots and the surrounding ZnSe matrix. In small mesas interdiffusion activation energy (EA) of less than 1eV was determined. This value of EA was half of that recorded for the Cd–Zn interdiffusion in large quantum dot ensembles, indicating that the sidewalls of the etched mesas play an important role in the observed diffusion process.

Enhanced Zn–Cd Interdiffusion and Bi-Exciton Formation in Self-Assembled CdZnSe Quantum Dots in Thermally Annealed Small Mesas. E.Margapoti, L.Worschech, A.Forchel, T.Slobodskyy, L.W.Molenkamp: Journal of Applied Physics, 2006, 100[11], 113111 (4pp)