Journal
JOURNAL OF APPLIED PHYSICS
Volume 110, Issue 9, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.3658020
Keywords
binding energy; electron-hole recombination; excitons; II-VI semiconductors; magnesium compounds; molecular beam epitaxial growth; plasma materials processing; semiconductor growth; semiconductor quantum wells; stacking faults; wide band gap semiconductors; zinc compounds
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Funding
- Walter Schottky Institut
- Deutsche Forschungsgemeinschaft via NAWACS [EI 518/2-1]
- EU [CP-IP 246334-2]
- Universitat Bayern e.V.
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ZnO/Zn1 - xMgxO single quantum well (SQW) structures with well widths d(W) between 1.1nm and 10.4 nm were grown by plasma-assisted molecular beam epitaxy both heteroepitaxially on c-plane sapphire and homoepitaxially on (000 (1) over bar)-oriented bulk ZnO. A significantly reduced Mg incorporation in the top barrier related to the generation of stacking faults is observed for heteroepitaxial samples. Exciton localization is observed for both types of samples, while an enhancement of the exciton binding energy compared to bulk ZnO is only found for homoepitaxial SQWs for 2nm <= d(W) <= 4 nm. Consistently, for homoepitaxial samples, the carrier dynamics are mainly governed by radiative recombination and carrier cooling processes at temperatures below 170 K, whereas thermally activated non-radiative recombination dominates in heteroepitaxial samples. The effects of polarization-induced electric fields are concealed for Mg concentrations x < 0.1 due to the reduction of the exciton binding energy, the screening by residual carriers as well as the asymmetric barrier structure in heteroepitaxial wells. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3658020]
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