Strong in-plane polarized intraband absorption in vertically aligned InGaAs/GaAs quantum dots

We present a midinfrared absorption study of an n-i-n structure containing two planes of strongly coupled In(0.5)Ga(0.5)As self-assembled quantum dots. We find that the dominant absorption occurs for light polarized in the growth plane (E//xy), contrasting with uncoupled dots which exhibit stronger absorption for light polarized in the growth direction (E//z) in the same energy range. Results from the coupled dot sample indicate that the confinement length in the growth direction is increased, lowering the energy of the s-like ground state and hybridizing p(x,y)-like excited states and wetting layer states. A significantly increased normal incidence photocurrent signal is measured for the sample containing coupled dots, relative to samples containing up to 30 layers of uncoupled dots, confirming the enhancement of the normal incidence absorption. (C) 2003 American Institute of Physics.