通过变温荧光光谱研究了ZnO激子发光的温度依赖特性.在6K的低温下,其光致发光主要来自束缚激子能量位于3.360eV,半宽为3meV的施主束缚激子发光.而随着测量温度的上升,自由激子及其声子辅助跃迁发光逐渐成为ZnO主要发光机制.文中详细讨论了ZnO荧光随温度的演变过程.特别是自由激子的声子伴线与自由激子发光峰之间的能量间距,随温度的上升逐渐偏离了其特征声子模能量,呈现不断缩小趋势.
Temperature dependent photoluminescence(PL)of ZnO single crystals was investigated.In the PL spectrum of ZnO measured at 6K,it is found that the strongest emission peak with a full width at half maximum(FWHM)of 3meV at 3.360eV comes from doner-bound-excitons of ZnO.As temperature increases,the emission from free exciton and its phonon sideband become stronger gradually comparing with doner-bound excitons and become dominant at room temperature.And the photoluminescence evolution of free exciton and its phonon sideband are discussed in detail.Especiallly,it is interested that the energy spacing between emission peaks of free excion and its phonon sidebands shrinks gradually and deviates the characteristic energy (72meV)of the Al-LO mode of ZnO with increasing temperature.
参考文献
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