Observation of coherent biexcitons in ZnO/ZnMgO multiple quantum wells at room temperature

Abstract

We have studied ZnO∕ZnMgO multiple quantum wells by spectrally resolved transient four-wave mixing with both one- and two-color excitations. The presence of an extended signal at negative interpulse delays in the two-color experiment is attributed to the two-photon coherence resulting from the generation of biexcitons. This technique provides a means to observe a transient four-wave mixing from biexcitons in the absence of any other signal, and thereby provides the first clear evidence that biexcitons are present in narrow ZnO∕ZnMgOquantum wells at room temperature. Dephasing times of the order of 100fs for the biexcitons are measured. Show more