Surface flattening during MOCVD of thin GaAs layers covering InGaAs quantum dots

Methods to re-establish a flat growth front on top of the corrugated surfac e of InGaAs quantum dots (QDs) during MOCVD are reported. Overgrowth temper atures at least 100 K higher than the low QD deposition temperature of 490 degreesC are required for a reduction of the corrugation. In order to avoid degradation of the QDs, however, the temperature must not be increased unl ess the QDs are buried by similar to 3 nm GaAs deposited at the QD growth t emperature. Application of an additional annealing step after deposition of the GaAs cap layer improves the surface flatness and leads to an improveme nt of the radiative recombination efficiency. Lasers grown using such an an nealing process for GaAs spacers of an InGaAs QD stack show lower threshold currents and higher internal quantum efficiency. (C) 2000 Elsevier Science B.V. All rights reserved.