The research and development of zinc selenide (ZnSe) based wide-gap II¡VVI materials and related blue/green light-emitting devices have significantly progressed since 1990. ZnSe is also a promising material for use in windows, lenses, output couplers, beam expanders, optically controlled switching, visible transmission and giant photo-resistivity. Recently, ZnSe has become an important material used as the window layer of CuInSe2-based solar cells . To improve device performance, it is necessary to reduce interface defects and improve epitaxial layer quality. However, ZnSe thin films on glass substrates with high reliability and applicability have not yet been developed.
In this study, a ZnSe buffer layer was firstly grown by SME during the initial stage of film growth; the film crystallinity could gradually be improved layer by layer with smaller thicknesses. While the lattice disorder of the buffer layer decreased rapidly after several cycles of SME growth, the interfacial lattice mismatch between the buffer layer and the ZnSe film deposited by MBD was reduced. Thus, ZnSe films with buffer layers demonstrated better crystallinity.
Initial growth stage evaluation of high-quality ZnSe films deposited on glass substrate was investigated. The self-limiting monolayer epitaxial (SME) process was used to pre-growth the buffer layer for a zinc selenide (ZnSe) film deposited. After alternating depositions for several cycles, the growth mode was changed to the molecular beam deposition (MBD) mode under growth conditions. Films deposited at substrate temperatures of 250¡V350¢XC and Se/Zn beam equivalent pressure (BEP) ratios of 0.77¡V1.87 were investigated.
The crystal structure and preferred orientation of as-grown ZnSe films were examined using X-ray diffraction (XRD) patterns. The optical properties of the ZnSe films were revealed by photoluminescence spectra.
The structure properties of as-deposited ZnSe films have been measured by X-ray diffraction (XRD) technique. The optimum film growth condition has been determined rapidly by comparing and analyzing the relative full width at half-maximum (FWHM) and peak intensity of XRD spectra. The composition of ZnSe films is determined by energy dispersive spectroscopic (EDS) analysis. Optical properties of ZnSe films are characterized by photoluminescence spectra. In addition, the structural parameters, crystallinity, lattice constant, grain size, strain, dislocation density and orientation of ZnSe film calculated are correlated with their growth conditions. The characteristics of the ZnSe films with and without a buffer layer were compared and discussed in detail.
Finally, our results demonstrate that how the quality of ZnSe film can be improved on glass substrates for application to various devices.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0728110-150844 |
| Date | 28 July 2010 |
| Creators | Huang, Chia-wei |
| Contributors | Tai-Fa Young, Bing-Hwai Hwang, Yeu-Long Jiang, Herng-Yih Ueng, G. M. Wu, Yuh-Fung Huang, Wei-Chu Hsu |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0728110-150844 |
| Rights | not_available, Copyright information available at source archive |
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