Evidence of “crossed” transitions in dots-in-a-well structures through waveguide absorption measurements

In-plane absorption measurements were performed at room temperature by means of a waveguide transmission setup on a Stranski-Krastanov InAs dots-in-a-well system emitting at 1.3 μm embedded in a p-i-n structure. The polarization dependence of quantum dot (QD) absorption was exploited to resolve its discrete and continuous spectral components and study them separately under reverse bias application. The quantum confined Stark effect observed in the discrete spectral component gave evidence of an upward built-in QD dipole of about 9.5× 10-29 C m. The continuous component was found to originate from electronic transitions involving a QD state and a quantum well state.