Investigation on the lasing characteristics of InAs/InGaAsP quantum dots with additional confinement structures

We report on morphological, optical, and lasing characteristics of InAs quantum dots (QDs) embedded in an In_0.69Ga_0.31As _0.67P_0.33 quantum well (having a bandgap energy corresponding to a wavelength of 1.35 μm (1.35Q-InGaAsP)), which formed a dot-in-a-well (DWELL) structure. This DWELL was further sandwiched in In _0.85Ga_0.15As_0.32P_0.68 layers (1.15 μm, 1.15Q-InGaAsP). A 2 monolayer-thick GaAs layer was simultaneously introduced right below the InAs QD layer in the DWELL structure (GDWELL). The emission wavelength of the InAs GDWELL was 1490 nm, which was slightly shorter than that of the InAs QDs embedded only in 1.15Q-InGaAsP layers. To evaluate the effects of the GDWELL structure on lasing characteristics, gain-guided broad-area (BA) and index-guided ridge-waveguide (RW) laser diodes (LDs) were fabricated. The BA-LDs with the InAs QDs embedded only in 1.15Q-InGaAsP layers did not show the lasing at room temperature (RT) even in pulsed mode. For the GDWELL structure, however, the lasing emissions from both the BA-LDs and RW-LDs were successfully achieved at RT in continuous-wave mode.