RADIATION CHARACTERISTICS OF INJECTION-LASERS BASED ON VERTICALLY COUPLED QUANTUM DOTS

We have studied injection lasers based on InGaAs/GaAs vertically coupl ed quantum dots (QD) grown by molecular beam epitaxy. The threshold cu rrent density decreases by one order of magnitude down to 90 A cm(-2) (300 K) with an increase of the number of QD stacks (N) up to 10. For N greater than or equal to 3 lasing occurs via the QD ground state up to room temperature. Differential efficiency increases with N up to 50 %. No change in range of high temperature stability of threshold curre nt density (J(th)) was observed, while the characteristic temperature (T-0) measured at 300 K increases from 60 to 120 K. Using InGaAs-AlGaA s QD with higher localization energy allowed us to decrease J(th) down to 60 A cm(-2) and to increase the differential efficiency up to 70%. (C) 1997 Academic Press Limited.