Effects of the well layer on the emission wavelength of InAs/InGaAs dot-in-a-well structure

InAs/InGaAs dot-in-a-well structures were grown by metal organic chemical vapor deposition at various In contents and thicknesses of InGaAs strained buffer layers (SBLs) and strain reducing layers (SRLs) in order to control the emission wavelength. On increasing the In content of an InGaAs SBL, the density and height of quantum dots (QDs) increased simultaneously. A red-shift of the emission wavelength from 1100 nm to 1290 nm was obtained by increasing the In content of the SRL. For further red-shift, the effects of the well-layer thickness were investigated. Reducing the SBL thickness did not make a significant difference to QD morphology; however, a red-shift up to 1380 nm was obtained. The In-Ga intermixing between QDs and the SBL was attributed to this red-shift. On the other hand, an increase in SRL thickness led to a red-shift due to the strain relaxation of QDs. The SRL-thickness effect was diminished when the thickness reached about 11 nm. With a 0.5-nm-thick SBL, the red-shift on increasing the SRL thickness was more obvious than that with a 2.0-nm-thick SBL. This relationship implies that the effect of intermixing due to the thick SBL canceled out the effect of the strain relaxation due to the SRL.