Laser diodes based on InGaAs quantum dots (QDs) operating at 1250nm with ultra-low threshold current densities of 66A/cm(2) transparency current densities of 52 A/cm(2), and high internal quantum efficiencies of 94% have been realized using alternative precursor MOCVD. Photoluminescence of the active QD stacks clearly indicate the requirement of varying growth parameters for subsequently deposited QD layers. The excellent performance of the QD lasers was obtained by adjusting the number of stacked QD layers to a limit given by the In content of the InGaAs strain-reducing layers grown on the QDs, and individual durations of the growth interruption after deposition for each QD layer. Results of investigations to further tune the emission wavelength towards 1.3 mu m are shown. (c) 2006 Elsevier B.V. All rights reserved.