Midinfrared absorption and photocurrent spectroscopy of InAs/GaAs self-assembled quantum dots

We report on a comparison between the midinfrared absorption and the photocurrent response of n-doped InAs/GaAs self-assembled quantum dots. The absorption, resonant at 160 meV, is polarized along the z growth axis of the dots. The photocurrent is dominated by a z-polarized resonance around 220 meV (5.6 mum wavelength). A weaker component of the photocurrent is observed for an in-plane polarized excitation. The photoresponse can be measured for a 0 V applied bias. The photoresponsivity is investigated as a function of the applied bias. The responsivity and the dark current exhibit an asymmetric profile versus the external bias. This asymmetry is correlated to the structural asymmetry of the quantum dot layers. (C) 2001 American Institute of Physics.