1-D electronic density of states for InAs/InP Quantum Dashes probed by scanning tunneling spectroscopy

Quantum Dashes (QDashes), some elongated and self-assembled semiconductor nanostructures are interesting candidates as building blocks for new laser devices with promising performances. To date, there was a lack of knowledge about the dimensionality of the confinement for carriers in such QDashes. We report on cross-sectional scanning tunneling microscopy and spectroscopy (X-STM/STS) performed on InAs(P)/InGaAsP/InP(001) QDashes, embedded in an optimized laser structure configuration. The active region consists of nine InAs(P) QDashes layers separated by InGaAsP barriers, sandwiched between a p-type and an n-type InP semiconductor. The STS measurements measured throughout the active region reveal a shift of the conduction band edges in agreement with built-in potential of the p-i-n junction. Furthermore we investigate the question of the dimensionality of the InAs(P) Q-Dashes. Local density of states measured on QDashes from layer to layer indicates a 1-D quantum-wire-like nature for these nanostructures whose squared wavefunctions were subsequently imaged by differential conductivity mapping.