A strain-balanced InAs quantum dot system was presented that had great potential in fabricating high-performance multi-layer quantum dot infra-red photodetector structures. The overall compressive strain caused by the formation of InAs quantum dots on InAlGaAs/InP was successfully balanced by inserting tensile-strained InGaAs layers immediately above quantum dot layers. The strain-balanced quantum dot structure permitted the stacking of a large number of defect-free quantum dot layers for increasing the size uniformity of quantum dots as well as the optical absorption, which were essential to the high-performance photodetector. As a first step towards the demonstration of a high-performance photodetector, a 50-layer strain-balanced InAs quantum dot structure was grown. No visible defect was detected by cross-sectional transmission electron microscopy. In addition, the intense and narrow line-width of the room-temperature photoluminescence spectrum indicated good optical quality.

Defect-Free 50-Layer Strain-Balanced InAs Quantum Dots Grown on InAlGaAs/InP for Infrared Photodetector Applications. Z.H.Zhang, C.F.Xu, K.C.Hsieh, K.Y.Cheng: Journal of Crystal Growth Volume, 2005, 278[1-4], 61-6