Normal-incidence far-infrared absorption of five-period InAs/GaAs quantum dots at room temperature

We report a normal-incidence far-infrared absorption above 10 μm of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy. The InAs QD layers are embedded in a GaAs matrix with Si δ-doping. The absorption spectrum in the far-infrared range observed at room temperature is attributed to the intersublevel transitions of the InAs QD layer above 10 μm. A Si δ-doped InAs QD sample with a five-period vertically stacked structure shows a photoluminescence spectrum at room temperature, attesting to the high quality of the InAs QDs. This result agrees with the strong normal-incidence far-infrared absorption observed in five-period InAs QD layers with Si δ-doping by using Fourier transform infrared spectroscopy at room temperature.