Coupling between magnetic/nonmagnetic semiconductor quantum dots in double-layer geometry

Abstract

Magneto-photoluminescence (PL) is used to study carrier transfer between self-assembled quantum dots (QDs) fabricated in the form of two adjacent QD layers separated by a thin barrier, one layer consisting of CdSe QDs and one of CdMnSe QDs in a ZnSe matrix. CdMnSe is a diluted magnetic semiconductor (DMS). In contrast to typical behavior of many low-dimensional DMS systems in which the application of a magnetic field B dramatically increases the PL intensity, in double-layer structures described above we observed a striking decrease of the PL intensity as a function of B. This effect indicates carrier tunneling from the CdSe to the CdMnSe dots as the ground state in the latter is lowered via the large Zeeman shift of the CdMnSe band edges.

Strong coupling in artificial semimagnetic Cd(Mn,Mg)Te quantum dot molecule

“…It is interesting to note a common character of the presented explanation of the spectral peculiarities as a result of the strong electron tunnel coupling between the QDs, as was found previously in self-organized CdMnSe double QDs by Lee et al [11]. On the other hand, different energy gaps in the CdMnTe and CdMnSe materials make the investigated system different from the one studied in Ref.…”

“…On the other hand, different energy gaps in the CdMnTe and CdMnSe materials make the investigated system different from the one studied in Ref. [11], where strong energy transfer to the internal transition of the Mn atoms ( 2 1…”

Magneto‐photoluminescence study on magnetic/non‐magnetic semiconductor coupled quantum dots

“…The PL intensities are normalized to the value at B = 0 T. The PL intensity of the DLQD signal systematically decreases when a magnetic field increases, in contrast to typical behavior for DMS systems, where the PL intensity increases with magnetic field. [12][13][14] Such anormalous magnetic field dependence of the PL intensity in a DMS system is at first glance quite surprising.…”

“…The broadening of the PL line (about 50 meV) is due to the inhomogeneity of size and composition of the QD ensemble in the system. Even though the PL intensity observed on the DLQDs is strong enough for a clear identification of the peak position and its shift in an applied magnetic field, we must emphasize that it is still an order of magnitude weaker than PL emission from the non-DMS QD sample [12]. Such reduction of PL intensity is commonly observed in Mn-containing wide-gap II-VI systems regardless of their geometry, and is attributed to energy transfer between the recombining excitons and internal transitions in the Mn 2+ ion.…”

“…Our DLQD structure consists of a DMS QD layer adjacent to a non-DMS QD layer. The potential of the CdSe QDs is expected to lie at (slightly) lower energy than that of CdMnSe dots because of the presence of Mn, which tends to slightly increases the band gap of the DMS material [12]. Thus the potential profile of the DLQD structure is slightly asymmetric at zero magnetic field.…”