Li掺杂ZnO薄膜的导电和发光特性

通过将含有原子数分数为2%锂的Zn-Li合金薄膜和金属锌薄膜在500℃氮气氛中退火2h,然后在700℃氧气氛下退火1h的方法分别制备出ZnO:Li和ZnO薄膜。Hall效应测量表明,其导电类型分别为p型和n型。通过He-Cd激光器的325nm线激发,测量了样品室温和低温(12K)光致发光光谱,并根据ZnO:Li薄膜的低温发光光谱特征,计算出Li相关受主能级位于价带顶137meV处。

Electrical and Optical Characteristics of Li-doped ZnO

The difficulty in the fabrication of p-type ZnOhinders the development of ZnO-based devices. Group-Ⅰand group-V elements substituting for Zn and Ocan respectively form the different acceptor dopants. Park C Hcalculated the energy levels of different acceptor dopants in ZnO, and it is found that group-Ⅰ elements substituting for Zn are of a shallower acceptor level than group-V elements substituting for O. Especially the acceptor level of Li substituting for Zn (Li_Zn) is 0.09 eV, which is the shallowest value among the energy levels of acceptor dopants in ZnO reported. However, when Li atom substitutes for Zn, it will easily be accompanied by the formation of interstitial Li (Li_i), which is likely to be shallow donor. This causes the p-type doping to be limited by the formation of a Li_Zn-Li_i complex donor. Based on above, Li was used as the acceptor dopant substituting for Zn in this work. In order to repress the formation of Li_i, nitrogen was used as a codopant with lithium by a two step annealing process to form Li_Zn-N complex acceptor.