From large to low height dispersion for self-organized InAs quantum sticks emitting at 1.55 μm on InP (001)

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Abstract
We show how the height dispersion of self-organized InAs/InP(001) quantum islands emitting at 1.55 μm was reduced by optimizing the epitaxialgrowth parameters. Low height dispersion was obtained when the InAs deposit thickness was much greater than the critical thickness for two-dimensional/three-dimensional growth mode transition, and when adatom surface diffusion was favored by increasing the growth temperature or reducing the arsenic pressure during the InAsgrowth. When these growth conditions are not respected, the multicomponent photoluminescencespectrum obtained is explained through the common interpretation of island height varying with monolayer fluctuation. In optimized growth conditions, the multicomponent spectrum obtained is interpreted as emission from fundamental and excited levels of InAs islands with low height dispersion.Transmission electron microscopy(TEM) imaging shows that these InAs islands are stick-like, 50–100 nm in length and 22±1.2 nm in width. Cross-sectional TEM reveals flat islands, shaped like truncated pyramids, with a very homogeneous height measured at 2.4 nm. A fundamental level linewidth of 22 meV at 8 K is associated to this very narrow height distribution. Such low photoluminescencelinewidth values are believed to be mainly due to the propensity of the InAs/InP(001) system to produce flat InAs islands with discrete height fluctuation.