Engineering electron and hole tunneling with asymmetric InAs quantum dot   molecules
  Most self-assembled quantum dot molecules are intrinsically asymmetric with inequivalent dots resulting from imperfect control of crystal growth. We have grown vertically-aligned pairs of InAs/GaAs quantum dots by molecular beam epitaxy, introducing intentional asymmetry that limits the influence of intrinsic growth fluctuations and allows selective tunneling of electrons or holes. We present a systemic investigation of tunneling energies over a wide range of interdot barrier thickness. The concepts discussed here provide an important tool for the systematic design and characterization of more complicated quantum dot nanostructures. 
A. S. Bracker, M. Scheibner, M. F. Doty, E. A. Stinaff, I. V.   Ponomarev, J. C. Kim, L. J. Whitman, T. L. Reinecke, D. Gammon