ZnS中Te等电子中心的时间分辨光谱研究

用时间分辨光谱研究了很大的Te组分范围内的ZnS_1-xTe_x（x=00 05—085）合金的发光动力学特性，结果表明：不同形态的Te等电子中心具有不同的辐射复 合寿命，从几个ns到几十个ns的范围内变化，当x＝015左右时，寿命达到最大值（约 40ns）.其物理机理源于不同的Te等电子中心具有不同的局域化特性.当Te组分较小时，等 电子中心从Te₁逐渐演变到Te₂，Te₃或Te₄ 时，相应发光寿命增加，表现出不断增强 的激子发光局域化特性；而当Te组分较大时，Te原子团变得较大，其局域势与基体原子势的 相互作用增强，等电子中心的局域化特性减弱，而基体价带扩展态特征变得明显起来，相应 发光寿命逐渐减小.还研究了激子束缚能随Te组分的变化以及发光强度随温度的变化关系， 所得结果进一步支持了时间分辨光谱研究所得到的结论. 关键词： ZnS 等电子中心 时间分辨光谱 局域态

Time-resolved photoluminescence of Te isoelectronic center in ZnS

The recombination dynamics of localized exciton in ZnS_1-xTe_{x ternary alloys has been investigated by time-resolved photoluminescence (PL) in a large Te concentration range from 0005 to 085. It is found that the radiativ e recombination lifetimes of different Te isoelectronic centers show a significa nt difference, varying from a few nanoseconds to tens of nanosecond. The lifetim e reaches a maximum of ～ 40 ns in the sample of x=015. The present result s could be understood in terms of the exciton localization effect. When the Te c oncentration is small, the Te isoelectronic centers evolve gradually from a sing le Te impurity (Te1) to the Te clusters (Ten). The exciton localization is enhanced, resulting in the increase of exciton recombination lifetime. When t he Te concentration is further increased, the Te clusters (Ten) becom e lar ge enough to hybridize the Te localized states and the host valence band states. Therefore, the excitons bound to Te isoelectronic centers become more or less d elocalized, resulting in a shorter lifetime. Furthermore, the concentration depe ndence of the exciton binding energy and the PL intensity variation with tempera ture have been mearsured. The results further confirm the above conclusion.}