Interdot spacing dependence of electronic structure and properties of multistacked InGaAs quantum dots fabricated without strain compensation technique

Abstract

We report on the electronic properties and band structure of multistacked quantum dots (QDs) fabricated without a strain compensation technique. It is possible to realize a small interdot spacing and introduce a strong quantum mechanical coupling. From the using temperature dependence, polarized photoluminescent spectra, and photoluminescent excitation experiments, we observe a markedly different behavior depending on the interdot spacing. These results evidence that minibands of electrons and holes are formed with interdot spacings of 7 and 3.5 nm, respectively. In addition, thise results are in good agreement with numerical calculations. We describe in detail the miniband formation and electronic structure of multistacked QDs with various interdot spacings of 10 nm or less.

Abnormal photoluminescence properties of InAs/InAsSb in-plane ultrahigh-density quantum dots

“…Not only the energy matching of QD energy levels but also the separation distance between neighboring QDs must be narrow enough for overlapping the electronic wavefunctions. According to the quantum mechanical coupling effect, 7) the separation distance between QDs is closely related to wavefunction localization and delocalization. Strong coupling of the electron wavefunction was reported to occur at interdot distances of less than 10 nm.…”

“…The electronic interactions of vertically multi-stacked QDs could be controlled by the separation distance between stacked dots and have been widely studied. 4,5) According to the previous reports, 6,7) the electronic state in strongly coupled QDs became delocalized as the interdot spacing is less than about 10 nm. While there have been reports on theoretical studies regarding in-plane strong coupling between adjacent QDs, 8,9) there are fewer experimental studies on self-assembled QDs due to low QD density and large inhomogeneous broadening of the QD size.…”

Demonstration of in-plane miniband formation in InAs/InAsSb ultrahigh-density quantum dots by analysis of temperature dependence of photoluminescence

“…As a result, the exciton state splits into an anti-bonding state (upper) and a bonding state (lower). 2,26) If the QD energy of QD1 is higher than that of QD2 (E 01 > E 02 ), the QD minimum energy is lowered by ( )…”

“…However, in the case of InAs QDs, since the effective mass of a hole is heavier than that of an electron, holes in the valence band of QDs are individually confined and do not interact with neighbors. 26) According to the theoretical calculation of zero-dimensional electronic states in the QD, it is known that the transition energy in the QD decreases in proportion to the γth power of the QD volume. 27,28) In the case of InAs UHD QDs on InAsSb WL, the transition energy was almost proportional to the −0.27th power of the QD volume, as reported previously.…”

InAs/GaAsSb in-plane ultrahigh-density quantum dot lasers

“…Consequently, a miniband is formed in the conduction band. 30) The reason the characteristic temperature is not so high is not only due to the inhomogeneous broadening of the QD energy levels, but due to the miniband formation.…”