| Summary: | 碩士 === 國立交通大學 === 物理研究所 === 87 === Abstract
The p-type ZnSe (ZnSe:N) and n-type ZnSe (ZnSe:Cl) films are grown by molecular-beam epitaxy (MBE).The photoluminescence (PL) spectroscopy is used to characterize the optical properties of these films with various concentration of dopants N and Cl and therefore describe the results specifically. The characteristics of the recombination emission between different impurity levels are studied by PL measurements. The impurity levels are ascribed to the complex defects due to various dopant concentrations, for instance, the donor-type complexes such as NSe-Zn-VSe and NZn-NSe of the N-doped ZnSe (ZnSe:N). The (NSe)n-Zn may play the role of a deep acceptor. And in the Cl-doped ZnSe film there are two complex defects, by ClSe-Zn and ClSe-VZn respective. The high N concentration of N-doped ZnSe causes the prominent red-shift of the donor-acceptor pair (DAP) recombination emission. The DAP peak becomes broaden and shifts to lower energy as the temperature is increased. Consequently, our result explores that the interact ion of the phonons and the exciton within the crystal.
The ZnSe:Cl PL spectra shows exhibits a very strong peak. Let is ascribed that the incorporated Cl atoms are located at the substitutional lattice sites of Se atoms, and thus behaves like a negative isoelectric center which may form a bound-exciton by binding a free hole. The spectra are the result of the recombine emission of these electron-hole pair. The excitons trapping at isoelectric center are located in a smaller region so that they have larger probability to recombine. And thus causes a peak with stronger intensity. Using the annealing technique, we make the material structure rearrange to reduce the inner vacancies. This result may raise the bound-exciton recombine energy and mediate the deep-level emission.
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