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

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