Optical properties of biexcitons in ZnS

Abstract

Characteristics of biexcitons in ZnS epitaxial layers with biaxial tensile strain have comprehensively been studied by means of photoluminescence excitation spectroscopy, magnetophotoluminescence spectroscopy, and time-resolved photoluminescence spectroscopy. Photoluminescence excitation measurement of biexcitons allowed us to observe two-photon absorption of biexcitons and to determine the biexciton binding energy of 8.0Ϯ1.2 meV. Under a magnetic field, the luminescence line due to the radiative recombination of light-hole free excitons slightly shifted to the lower-energy side ͑about 0.3 meV at 9 T͒. On the other hand, the luminescence line due to the radiative recombination of biexcitons split into two components. This splitting ͑about 1.2 meV at 9 T͒ originated from the Zeeman splitting of light-hole free excitons in the final state of the optical transition for biexciton luminescence. In addition, the luminescence decay times of both light-hole free excitons and biexcitons were estimated to be about 130 and 80 ps, respectively. The observed temporal behavior was consistent with the expected recombination dynamics between excitons and biexcitons.

Effects of magnetic fields on free excitons in CuInSe2

“…Similar analysis of diamagnetic shifts has been reported for free excitons in ZnS [17]. Recently diamagnetic shifts under magnetic fields up to 10 T have been measured in CuInS 2 [18].…”

Intrinsic exciton transitions in high-quality ZnO thin films grown by plasma-enhanced molecular-beam epitaxy on sapphire substrates

“…It can be seen that the integrated PL intensity of the XX band increases superlinearly with increasing excitation intensity. This result is quite different from that of impurity-or defect-related luminescence, which we would expect to be saturated at relatively high excitation powers, indicating that peak XX is associated with 29,30 formed by the frequent collisions in high concentration excitons. This result confirms that the films are of excellent quality, since the density of defects is so low that the excitons can avoid excessive scattering by impurities and crystalline defects before they form biexcitons.…”

Excitonic Properties of ZnS Quantum Wells in ZnMgS

“…The effective exciton g-values measured for both LH and HH excitons are summarized in Table 1 where it can be seen that the LH value is greater than that for the HH for the range of well widths investigated. Our results are larger than the g-values reported in [9] for non-strained bulk ZnS from PL measurements on biexcitons in magnetic fields up to 9 T. This behaviour is the result of the splitting of the LH and HH exciton states due to the tensile strain in the ZnS well, resulting in the LH being the uppermost valence band. As a result the ordering of the LH spin states is reversed leading to a Zeeman splitting for the exciton where the splittings of the electrons and holes are additive.…”