Optimizing the growth of 1.3-μm InAs/InGaAs dots-in-a-well structure: Achievement of high-performance laser

The structural and optical properties of single- and multi-layer GaAs-based 1.3-μm InAs/InGaAs dots-in-a-well (DWELL) structures have been optimized to improve the performance of quantum dot (QD) lasers. A strong dependence of the InAs QD density and the QD emission wavelength on the In composition of InGaAs well has been demonstrated for single-layer samples. The optimum In composition in the well for 1.3-μm applications is obtained to be 15%. The effects of growth temperature of the spacer layers (SPLs) are investigated using a 5-layer structure. It is found that the growth temperature of GaAs SPLs has a pronounced effect on both the structural and optical properties of the InAs QDs. Dislocations are introduced in the second and subsequent QD layers for samples where the GaAs SPLs are deposited at a low temperature of 510 °C. By incorporating a high-temperature (580 °C) growth step for the GaAs SPLs, dislocation formation is inhibited and a high level of inter-layer dot uniformity is achieved. An extremely low continuous wave room-temperature threshold current density of 39 A/cm2 is demonstrated for an as-cleaved 5-layer device with emission at 1.306 μm and ground-state operation up to 100 °C.