Photoluminescence and lasing characteristics of InGaAs∕InGaAsP∕InP quantum dots

The $\mathrm{InGaAs}$ quantum dots (QDs) were grown with $\mathrm{InGaAsP}\left({\lambda }_g=1.0–1.1\mu \mathrm{m}\right)$ barrier, and the emission wavelength was controlled by the composition of $\mathrm{InGaAs}$ QD material in the range between 1.35 and $1.65\mu \mathrm{m}$ . It is observed that the lateral size increases and the height of the QDs decreases with the increase in relative concentration of trimethylgallium to trimethylindium supplied during $\mathrm{InGaAs}$ QD growth. It is seen that the higher concentration of group III alkyl supply per unit time leads to higher QD areal density, indicating that the higher concentration causes more QDs to nucleate. By optimizing the growth conditions, the QDs emitting at around $1.55\mu \mathrm{m}$ were grown with an areal density as high as $8\times {10}^{10}{\mathrm{cm}}^{-2}$ . The lasing action between the first excited subband states at the wavelength of $1.488\mu \mathrm{m}$ has been observed from the ridge waveguide lasers with five QD stacks up to $260\mathrm{K}$ . The threshold current density of $3.3\mathrm{kA}∕{\mathrm{cm}}^2$ at $200\mathrm{K}$ and a characteristic temperature of $118\mathrm{K}$ were measured.