Intra-valence band transitions in self-assembled InAs∕GaAs quantum dots studied using photocurrent spectroscopy

We present a polarization-dependent study of the intra-valence band photocurrent signal in p-type self-assembled InAs∕GaAs quantum dots (QDs). The observed transitions are found to be strongly polarized in the quantum dot plane and associated with hole transitions from the dot states to the wetting layer states. Photocurrent spectra from p-doped QD samples are compared with photocurrent spectra from identically grown n-type QD samples. At 10K, the magnitude of the photocurrent signal is found to be smaller for p-type QD samples, compared with n-type QD samples. However, the rapid growth of the signal with increasing temperature due to thermal activation of holes from the light hole wetting layer states results in a comparable photoresponse to the n-type QDs at 50K.