Improved optical confinement in 1.55 micrometer InAs/GaInAsP quantum dot lasers grown by MOVPE
MOVPE-grown InAs quantum dots (QDs) implemented as active layers in 1.55 micrometer emitting InGaAsP/InP broad-area laser devices show improved characteristics with respect to previous MOVPE-based lasers and are now competitive with their MBE-grown counterparts. On the other hand, short devices exhibit markedly higher thresholds than quantum well lasers with an identical number of periods due to a low optical confinement. Increasing the QD density, the number of stacked QD layers and reducing the QD layer spacing is applied to improve the optical confinement and hence the laser characteristics. Increase of the number of stacked layers is demonstrated to result in a substantial improvement of the optimum length, while reduction of the spacer thickness was not found to influence device behaviour. Based on the described results laterally single mode buried heterostructure type lasers and semiconductor optical amplifiers were fabricated.