Abstract
A-plane-oriented ZnO epilayers grown by plasma-assisted molecular beam epitaxy were studied with respect to their optical properties. 10K-photoluminescence (PL) and reflectivity were used to analyze various 2 µm-thick ZnO films etched at different etching profile. The PL spectra show the band emission of the structures become narrower when the etching profile increase. At 0.75 µm etching profile, two structures at 3.38 eV corresponding to the A-free exciton transition and at 3.41 eV corresponding to the B-free exciton transition and the Y line were observed in the 10K PL spectrum providing that the optical properties of the ZnO sample are preserved and enhanced. Key words: Excitonic, photolumescence, wet-chemical etching, a-plane ZnO.
Highlights
As a wide bandgap (Eg=3.37 eV) semiconductor, ZnO has attracted considerable attention due to its potential applications, such as ultraviolet light-emitting devices and laser devices (Zhang et al, 2002)
At 0.75 μm etching profile, two structures at 3.38 eV corresponding to the A-free exciton transition and at 3.41 eV corresponding to the B-free exciton transition and the Y line were observed in the 10K PL spectrum providing that the optical properties of the ZnO sample are preserved and enhanced
In the paper, we report on the optical properties of wet etching a-plane ZnO films
Summary
As a wide bandgap (Eg=3.37 eV) semiconductor, ZnO has attracted considerable attention due to its potential applications, such as ultraviolet light-emitting devices and laser devices (Zhang et al, 2002). Compared with other wide bandgap materials, ZnO has a larger exciton binding energy (60 meV) (Zhang et al, 2002; Look, 2001), which paves the way for an intense near band edge excitonic emission at room (Bagnall et al, 1997) and even higher temperatures. A notable discovery in ZnO thin film materials is the observation of the ultraviolet (UV)-stimulated emission induced by the exciton–exciton scattering at moderate pumping intensity (Yu et al, 1997; Cao, 1998). These results show that ZnO is a suitable candidate for optoelectronic device applications in the ultraviolet region.
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