Development of Blue-Emitting EL devices with High Color-Purity and Brightness

本研究以金属有机分子束沉积法（MOMBD）生长的掺Tm的ZnS为材料，研制高色纯度和高亮度的蓝色电致发光器件。研究结果总结如下。首次以二乙基锌和二乙基硫或硫化氢为锌源和硫源，以元素Tm为掺杂剂，采用MOMBD技术在GaAs和玻璃衬底上成功生长了掺Tm的ZnS薄膜.生长的薄膜显示出蓝色光致发光，这归因于Tm^<3+>离子内的f-f跃迁。研究了Tm^<3+> inos的跃迁过程，并与薄膜和粉末样品的结果进行了比较。光致发光和电致发光测量表明，Tm^<3+>离子的主要激发过程不是由热电子直接激发，而是由ZnS基质的能量转移间接激发.为了提高蓝光发射和激发效率，设计了Tm调制掺杂的电致发光器件发光层。根据第2.4节中描述的结果，对结构的参数进行了优化。ZnS：用MOMBD生长了由δ掺杂层组成的Tm层，发现其发光特性取决于掺杂参数，δ掺杂Tm的片浓度和相邻片之间的距离。How13EA\：二次离子质谱测量已经表明，δ掺杂层的深度分布对于本发明目的而言不够陡峭。所观察到的浓度展宽还有待于详细研究以进一步改善13 EAl：n的不稳定性。

This research aims at the development of blue-emitting electroluminescence(EL)devices with high color-purity and brightness based on Tm-doped ZnS grown by metalorganic molecular beam deposition (MOMBD). The results of the study are summarized below.1. Tn-doped ZnS films have been successfully grown on GaAs and glass substrates by MOMBD, for the first time, using diethylzinc and diethyl sulfide or hydrogen sulfide as Zn and S sources and elemental Tm as the dopant.2. The grown films have shown blue photoluminescence which is ascribed to the f-f transitions within Tm^<3+> ions. The transition processes in Tm^<3+> inos were investigated and compared with the results of film and powder samples. Photoluminescence a13EA\ : nd electroluminescence measurements have indicated that the dominant excitation process of Tm^<3+> ions would be not a direct excitation by hot electrons but an indirect excitation by energy transfer from the ZnS matrix.3. The light-emitting layr with Tm-modulation-doped structures for EL devices have been designed for improving the efficiencies of blue emission and excitation. The parameters of the structure have been optimized the basis of the result described i13EA\ : n section 2.4. ZnS : Tm layrs consisting of delta-doped layrs have been grown by MOMBD.It has been found that the luminescence properties depend on the doping parameters, e.g., sheet concentration of delta-doped Tm and distance between the adjacent sheets. How13EA\ : ever, secondary ion mass spectroscopy measurements have shown that depth profile of delta-doped layrs was not abrupt enough for the present purpose. The observed concentration broadening is yet to be investigated in detail for further improvement i13EA\ : n the abruptness.