Quantum dot infrared photodetectors

Self-assembled strained semiconductor nanostructures have been grown on GaAs substrates to fabricate quantum dot infrared photodetectors. State-filling photoluminescence experiments have been used to probe the zero-dimensional states and revealed four atomic-like shells (s,p,d,f) with an excitonic intersublevel energy spacing which was adjusted to ∼60 meV. The lower electronic shells were populated with carriers by n doping the heterostructure, and transitions from the occupied quantum dot states to the wetting layer or to the continuum states resulted in infrared photodetection. We demonstrate broadband normal-incidence detection with a responsivity of a few hundred mA/W at a detection wavelength of ∼5 μm.