One and three-stack quantum dot lasers with very low threshold current density

Summary form only given. Quantum dot lasers with the dots-in-a-well (DWELL) structure have demonstrated very low threshold current densities. In particular, DWELL lasers with a single layer of InAs dots in an In/sub 0.15/Ga/sub 0.85/As well have demonstrated threshold current densities as low as 16 A-cm/sup -2/, which is the lowest threshold current density of any semiconductor laser. However, there are potential limitations to these lasers. Even though the ground state lasing threshold current density is very low, the ground state also has low saturated modal gain (/spl sim/4.5 cm/sup -2/). At a cavity length or 4 mm, the first excited state emission can be observed at high current levels. When the cavity length is further decreased increasing the cavity loss, lasing is purely from excited states. Also, the average T/sub 0/ value of these 1-DWELL lasers is only 45 K between 10/spl deg/C and 80/spl deg/C, lower than that reported by other groups for QD lasers. Three DWELL layers are used to increase the ground state gain and T/sub 0/ value. A quantum well laser is also grown to study limitations on the T/sub 0/ value of the DWELL structure.