Abstract
The transient terahertz signal generated by electron diffusion that was excited by an ultrashort pulse was observed to vary with the potential structure around the surface. The formation of InAs quantum dots caused the strain field and the nitrogen atoms to further modify the potential structure around the quantum dots. The terahertz signal that was observed for various pump energies exhibited an interesting phase change. Further, the change in terahertz dynamics originated from the formation of a dilute nitrogen layer around the quantum dots. Furthermore, this change depends on the position of the nitrogen-doped layer. The results of this study provide important information for controlling the optical properties of quantum dots.
Highlights
Control of the optical properties of self-assembled quantum dots (QDs) is essential for device applications such as in lasers [1,2,3], single photon sources [4,5,6], and solar cells [7,8,9]
We reported the phase inversion of a THz wave emitted from a GaAs crystal that included InAs QDs, which was attributed to the lattice-mismatched strain [26]
The samples used in this study were self-assembled InAs QDs covered by nitrogen atoms with or
Summary
Control of the optical properties of self-assembled quantum dots (QDs) is essential for device applications such as in lasers [1,2,3], single photon sources [4,5,6], and solar cells [7,8,9]. Covering the InAs. QDs with nitrogen atoms has been reported as one of the control methods [16,17,18,19,20,21]. By covering the InAs QDs with nitrogen atoms, the photoluminescence (PL) energy decreases because of the strain relief; further, the PL intensity decreases because of an increase in the non-radiative recombination center. These are recovered by the insertion of a GaAs spacer; the PL energy and intensity increases. In this study, we discuss the effect of using a nitrogen layer to cover QDs on the time-domain THz signal. THz signals is discussed from the aspect of the effects of the formation of a thin thin nitrogen-doped layer
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