Optical and lasing characteristics of 1.55 μm InGaAs/InGaAsP/InP quantum dots grown by MOCVD

The InGaAs quantum dots (QDs) were grown with InGaAsP (λ_g = 1.0∼1.1 μm) barrier and the emission wavelength was controlled by the composition of InGaAs QD material in the range between 1.35 and 1.65 μm. It is observed that the lateral size increases and the height of the QDs decreases with the increase in relative concentration of trimethylgallium (TMGa) to trimethylindium (TMIn) supplied during 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 μm were grown with an areal density as high as 8 × 10¹⁰ cm^-2. The lasing action between the first excited subband states at the wavelength of 1.488 μm has been observed from the ridge waveguide lasers with 5 QD stacks up to 260 K. The threshold current density of 3.3 kA/cm² at 200 K and a characteristic temperature of 118 K were measured.