Time resolved photoluminescence studies of Zn–Se–Te nanostructures with sub‐monolayer quantities of Te grown by molecular beam epitaxy

Abstract

We investigate triple-delta-doped ZnSe:Te samples grown with different Te/Zn flux ratios using timeresolved photoluminescence (TRPL). We show that the properties of the TRPL of both samples are consistent with the presence of quantum islands with a type-II band alignmrnt. Moreover, from the comparison of the PL, we show that higher Te/Zn flux ratio during the growth leads to the formation of larger quantum islands. [2]), there is formation of type-II quantum islands (QI), which contribute to photoluminescence (PL) with the maximum at ~2.46-2.51 eV ("green band"). In this paper, we investigate the effect of Te/Zn flux ratio used during the growth on such quantum structures using timeresolved photoluminescence (TRPL). Specifically, we compare two samples grown by molecular beam epitaxy: sample A grown with a Te/Zn flux ratio of ~0.44 and sample B grown with a Te/Zn flux ratio of ~0.26. Both samples were grown with the same Te flux. We shall discuss the spectrally resolved timedependent PL and the PL decay characteristics as well as their dependence on excitation intensity and temperature (T). We shall show that the PL of these two samples originates from type-II quantum islands (QIs) and that the higher Te/Zn flux ratio and/or lower Zn fluxes leads to larger QIs.

Crystallographic and Photophysical Analysis on Facet‐Controlled Defect‐Free Blue‐Emitting Quantum Dots

“…The ZnSe inner shelling process resulted in a redshift in the steady-state absorption and PL spectra, suggesting a delocalization of the electrons over the ZnSe inner shell. The holes are relatively confined in the Te isoelectronic centers of the core [18,19] and the electrons are delocalized over the ZnSe shell due to the quasitype II band alignment of ZnSeTe/ZnSe heterostructures. [20,21] ZnS outer shelling led to improved QY, suggesting strong confinement of optically excited charge carriers by the ZnS outer shell (Figure S1b, Supporting Information).…”

“…The size of the Te clusters has a direct impact on the valence band maximum (VBM) energy, with larger clusters leading to higher quantum confinement in the core and, consequently, a higher VBM and a slower recombination process. [18,21] Te as a single atom does not possess sufficient binding energy to trap holes, but as part of Te clusters, it can effectively bind holes. [19,21,39,40] The "smaller Te cluster emission" represents the emission from Te dyads, while the "larger Te cluster emission" corresponds to emissions from Te clusters composed of three or more Te atoms.…”

Radiative transitions in stacked type-II ZnMgTe quantum dots embedded in ZnSe

“…The value of E A1 $ 3 meV is significantly lower than the free exciton binding energy of either ZnSe 45 ($20 meV) or ZnTe 45 ($13 meV) but in the range of the values previously reported for ZnTe/ZnSe type-II QDs. 5,46,47 We attribute the activation energy, E A2 $ 116 meV to the ionization of the holes, which thermally escapes after making a transition from the QD ground state to the barrier. The activation energy, E A2 $ 116 meV is smaller compared to 178 meV reported for ZnTe/ZnSe QD; 15 this is expected because of lowering of the valence band offset with introduction of Mg (see detailed discussion in Sec.…”

“…9. The behavior of temperature dependent on the characteristic decay time, s c can be fitted to the following expression: 5,46,49 …”