Single photoelectron detection after selective excitation of electron heavy-hole and electron light-hole pairs in double quantum dots

We demonstrate the real-time detection of single photogenerated electrons in lateral double quantum dots made in AlGaAs/GaAs/AlGaAs quantum wells with either a thin (20 nm) or a thick (100 nm) AlGaAs barrier layer. The observed photon energy and power dependencies of the photoelectron detection efficiency both indicate that the trapped photoelectrons are predominantly generated in the buffer layer followed by tunneling into one of the two dots for the thin barrier sample, whereas they are directly generated in the well in the thick barrier sample. Single photoelectron detection after selective excitation of the heavy- and light-hole state in the dot is well resolved in the latter case. This ensures the applicability of our quantum well-based quantum dot systems for the coherent projection from single photon polarization to single electron spin states.