title: One-Dimensional Nature of InAs/InP Quantum Dashes Revealed by Scanning Tunneling Spectroscopy.
abstract: We report on low-temperature cross-sectional scanning tunneling microscopy and spectroscopy on InAs(P)/InGaAsP/InP(001) quantum dashes, embedded in a diode-laser structure. The laser active region consists of nine InAs(P) quantum dash layers separated by the InGaAsP quaternary alloy barriers. The effect of the p-i-n junction built-in potential on the band structure has been evidenced and quantified on large-scale tunneling spectroscopic measurements across the whole active region. By comparing the tunneling current onset channels, a consistent energy shift has been measured in successive quantum dash or barrier layers, either for the ground state energy of similar-sized quantum dashes or for the conduction band edge of the barriers, corresponding to the band-bending slope. The extracted values are in good quantitative agreement with the theoretical band structure calculations, demonstrating the high sensitivity of this spectroscopic measurement to probe the electronic structure of individual nanostructures, relative to local potential variations. Furthermore, by taking advantage of the potential gradient, we compared the local density of states over successive quantum dash layers. We observed that it does not vanish while increasing energy, for any of the investigated quantum dashes, in contrast to what would be expected for discrete level zero-dimensional (0D) structures. In order to acquire further proof and fully address the open question concerning the quantum dash dimensionality nature, we focused on individual quantum dashes obtaining high-energy-resolution measurements. The study of the local density of states clearly indicates a 1D quantum-wirelike nature for these nanostructures whose electronic squared wave functions were subsequently imaged by differential conductivity mapping.
authors.affiliation: †CNRS Laboratory for Photonics and Nanostructures, Route de Nozay, 91460 Marcoussis, France.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Papatryfonos
authors.affiliation: †CNRS Laboratory for Photonics and Nanostructures, Route de Nozay, 91460 Marcoussis, France.
authors.forename: Guillemin
authors.initials: G
authors.lastname: Rodary
authors.affiliation: †CNRS Laboratory for Photonics and Nanostructures, Route de Nozay, 91460 Marcoussis, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: David
authors.affiliation: ‡III-V lab, A Joint Lab of "Alcatel Lucent Bell Laboratories", "Thales Research and Technology", and "CEA Leti", Route de Nozay, 91460, Marcoussis, France.
authors.forename: François
authors.initials: F
authors.lastname: Lelarge
authors.affiliation: †CNRS Laboratory for Photonics and Nanostructures, Route de Nozay, 91460 Marcoussis, France.
authors.forename: Abderrahim
authors.initials: A
authors.lastname: Ramdane
authors.affiliation: †CNRS Laboratory for Photonics and Nanostructures, Route de Nozay, 91460 Marcoussis, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Girard
keywords: Dimensionality nature of nanostructures; InAs/InGaAsP/InP(001) semiconductor quantum dashes; density of states; p-i-n junction; scanning tunneling spectroscopy; wave function imaging