Defect-free 50-layer strain-balanced InAs quantum dots grown on InAlGaAs/InP for infrared photodetector applications

We present a strain-balanced InAs quantum dot (QD) system that has great potential in fabricating high-performance multilayer QD infrared photodetector structures. The overall compressive strain caused by the formation of InAs QDs on InAlGaAs/InP is successfully balanced by inserting tensile-strained InGaAs layers immediately above QD layers. The strain-balanced QD structure allows stacking a large number of defect-free QD layers for increasing the size uniformity of QDs as well as the optical absorption, which are essential to the high-performance photodetector. As the first step toward the demonstration of a high-performance photodetector, a 50-layer strain-balanced InAs QD structure was grown. No visible defect was detected from the cross-sectional transmission electron microscopy measurements. In addition, the intense and narrow linewidth of the room temperature photoluminescence spectrum indicate a good optical quality of the structure.