Lateral photoconductivity and bound states of self-assembled Ge/Si quantum dots

We have investigated lateral conduction mid-infrared photodetectors using the photoionization of holes in the valence band of self-assembled Ge/Si quantum dots. A mid-infrared photocurrent signal was observed in the photon energy range of 140-400 meV resulting from an intersubband transition in the valence band of self-assembled Ge quantum dots and subsequent lateral transport of photoexcited carriers in the SiGe conduction channel. The peak responsivity was 134 mA W^-1 at a photon energy of 240 meV at T = 10 K. Furthermore, the band structure of the Ge QD system was estimated using electrical and optical measurements.