In-plane photocurrent of self-assembled ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\left(311\right)\mathrm{}B$ quantum dot arrays

On self-assembled ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\left(311\right)\mathrm{}B$ quantum dots (QD’s), photocurrent in the plane of QD arrays was measured under irradiation with wavelengths longer than 850 nm (1.46 eV). A sample with rather inhomogeneous QD sizes shows hopping conduction, indicating the localization of carriers in individual QD’s. A two-dimensional QD superlattice, consisting of highly ordered and homogeneously sized QD’s, exhibits negative differential conductance (NDC), i.e., photocurrent decrease with increasing applied voltage, in a limited electric-field range. The pre-NDC conduction is argued to arise from the miniband, which is evidenced by the photoluminescence, while the post-NDC conduction is found to be hopping as in a localized QD system, suggesting a miniband destruction under an in-plane electric field as low as $\sim {10}^3{\mathrm{V}\mathrm{}\mathrm{cm}}^{\mathrm{-}1}.$ The miniband transport is likely controlled by two-dimensional acoustic-phonon scattering.