Effect of deposition method on the density of InAs/InGaAs quantum dot

InAs self-organized quantum dots covered with In/sub 0.33/Ga/sub 0.67/As layer have been grown on GaAs substrates by gas-source molecular beam epitaxy. With three different deposition methods for growing the InGaAs capping layer, the quantum-dot density can be controllably changed from 2.3/spl times/10/sup 10/ to 1.7/spl times/10/sup 11/ cm/sup -2/. Photoluminescence at 1,318nm of quantum dots with the dot density as high as 7.6/spl times/10/sup 10/ cm/sup -2/ can be achieved by sub-monolayer deposition (SMD) capping method. As-cleaved 3.98-mm-long laser diode using triple stacks of InAs/InGaAs quantum dots with SMD method demonstrates a lasing wavelength of 1,305nm and a threshold current density of 360A/cm/sup 2/. The ground-state saturation gain of 16.6cm/sup -1/ is achieved due to the high dot density.