Ultrafast spectroscopy of ZnO/ZnMgO quantum wells

Abstract

We review recent work studying the dynamics in zinc oxide quantum wells (QWs) using ultrafast optical spectroscopy. These materials present exciting possibilities for optoelectronic device applications. In order to develop these applications, it is important to understand the mechanisms of the electronic processes occurring in ZnO/ZnMgO QWs. In this review, we discuss the excitonic lifetime and the impact of the internal electric field, the potential profile, phonons, and defects. We also discuss coherence dynamics and the observation of biexcitons at room temperature.The ZnO QW sample appears clear to visible light, but absorbs and radiates in the near UV on laser excitation.

Carrier recombination dynamics in Si doped InN thin films

“…The variation of decay time with photon energy is similar to the case of disordered semiconductor alloy systems which are well-known for having carrier localization. 13 Gourdon and Lavallard 12 developed a model under the assumption that the overall decay rate is equal to the sum of the radiative recombination rate and transfer rate to the lower energy localized states. All of the nonradiative decay rates except for the transfer rate are neglected.…”

“…Moreover, the localization effect has been studied by analyzing the PL spectra at different temperatures. 4-11 The dependence of the PL decay time on emission energy also speculates upon the carrier localization effect 12,13 and can be used to investigate carrier localization in InN. Therefore, the mechanism of the PL formation in InN is controversial.…”

Diffusion and population dynamics of excitons in c-axis grown ZnO quantum wells

“…In order to implement devices based on such structures, it is important to understand their optical and electronic properties. Previous work has explored the exciton recombination dynamics and significance of the quantum confined Stark effect (QCSE) in a range of MBE grown quantum well (QW) systems [2,3,4]. Very little, however, has been reported regarding exciton transport properties in such quantum wells and the role of defects and interface roughness, particularly lateral to the heterointerfaces.…”

Recombination dynamics and screening of the internal electric field inZnO/ZnxMg1−xOmultiple quantum wells

“…2 Of particular interest are the superior exciton and biexciton binding energies ͑ZnO 60 and 15 meV, GaN 25 and 5.3 meV, respectively͒, [4][5][6] which give advantages to ZnO over GaN when considering oscillator strength and efficient light absorbing/emitting devices. 7 By integrating these materials into quantum-well ͑QW͒ structures, not only is there the opportunity to tune the transition energy but also the exciton and biexciton binding energies can be even larger; hence these structures are of considerable interest. 8,9 Growth of ZnO/ZnMgO quantum wells is preferentially c-axis oriented, which, to the detriment of a number of properties, leads to an internal electric field across the quantum well and the quantum-confined Stark effect ͑QCSE͒.…”