InAs/InGaAs/GaAs coupled quantum dot laser with predeposited InAs seed layer

We report a coupled quantum dot (QD) structure for long wavelength laser applications. The structure comprises an InAs seed layer and a second InAs QD layer capped with an In0.33Ga0.67As capping layer. Cross-sectional transmission electron microscopy (TEM) images show a vertical alignment between the QD stacks, which causes the coupled QD sample to have a larger dot size and a lower dot density than the control sample. The laser with the coupled QD structure exhibits a markedly longer emission wavelength and a slightly higher threshold current density than lasers with a conventional QD structure. indicating that the coupled QD structure has potential for long wavelength applications. © 2006 The Japan Society of Applied Physics.